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ScrollView-vs-NestedScrollView

Created 7 months agoDiff never expires

360 removals

605 lines

372 additions

611 lines

Google Git

android / platform / frameworks / base / jb-release / . / core / java / android / widget / ScrollView.java

android / platform / frameworks / support / refs/heads/androidx-main / . / core / core / src / main / java / androidx / core / widget / NestedScrollView.java

blob: ebc54f4527c8165cac4cc387d16b7f6d90bbf0e5 [file] [log] [blame]

blob: 8eebc918c45dd39c7538fa4529b184fb01dfa92e [file] [log] [blame]

* Licensed under the Apache License, Version 2.0 (the "License");

* you may not use this file except in compliance with the License.

* You may obtain a copy of the License at

* http://www.apache.org/licenses/LICENSE-2.0

* Unless required by applicable law or agreed to in writing, software

* distributed under the License is distributed on an "AS IS" BASIS,

* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

* See the License for the specific language governing permissions and

* limitations under the License.

package android.widget;

package androidx.core.widget;

import com.android.internal.R;

import static androidx.annotation.RestrictTo.Scope.LIBRARY;

import static androidx.annotation.RestrictTo.Scope.LIBRARY_GROUP_PREFIX;

import android.content.Context;

import android.content.res.TypedArray;

import android.graphics.Canvas;

import android.graphics.Rect;

import android.hardware.SensorManager;

import android.os.Build;

import android.os.Bundle;

import android.os.StrictMode;

import android.os.Parcel;

import android.os.Parcelable;

import android.util.AttributeSet;

import android.util.Log;

import android.util.TypedValue;

import android.view.FocusFinder;

import android.view.InputDevice;

import android.view.KeyEvent;

import android.view.MotionEvent;

import android.view.VelocityTracker;

import android.view.View;

import android.view.ViewConfiguration;

import android.view.ViewDebug;

import android.view.ViewGroup;

import android.view.ViewParent;

import android.view.accessibility.AccessibilityEvent;

import android.view.accessibility.AccessibilityNodeInfo;

import android.view.animation.AnimationUtils;

import android.widget.EdgeEffect;

import android.widget.FrameLayout;

import android.widget.OverScroller;

import android.widget.ScrollView;

import androidx.annotation.DoNotInline;

import androidx.annotation.NonNull;

import androidx.annotation.Nullable;

import androidx.annotation.RequiresApi;

import androidx.annotation.RestrictTo;

import androidx.annotation.VisibleForTesting;

import androidx.core.R;

import androidx.core.view.AccessibilityDelegateCompat;

import androidx.core.view.DifferentialMotionFlingController;

import androidx.core.view.DifferentialMotionFlingTarget;

import androidx.core.view.MotionEventCompat;

import androidx.core.view.NestedScrollingChild3;

import androidx.core.view.NestedScrollingChildHelper;

import androidx.core.view.NestedScrollingParent3;

import androidx.core.view.NestedScrollingParentHelper;

import androidx.core.view.ScrollingView;

import androidx.core.view.ViewCompat;

import androidx.core.view.accessibility.AccessibilityNodeInfoCompat;

import androidx.core.view.accessibility.AccessibilityRecordCompat;

import java.util.List;

/**

* Layout container for a view hierarchy that can be scrolled by the user,

* NestedScrollView is just like {@link ScrollView}, but it supports acting

* allowing it to be larger than the physical display. A ScrollView

* as both a nested scrolling parent and child on both new and old versions of Android.

* is a {@link FrameLayout}, meaning you should place one child in it

* Nested scrolling is enabled by default.

* containing the entire contents to scroll; this child may itself be a layout

* manager with a complex hierarchy of objects. A child that is often used

* is a {@link LinearLayout} in a vertical orientation, presenting a vertical

* array of top-level items that the user can scroll through.

* You should never use a ScrollView with a {@link ListView}, because

* ListView takes care of its own vertical scrolling. Most importantly, doing this

* defeats all of the important optimizations in ListView for dealing with

* large lists, since it effectively forces the ListView to display its entire

* list of items to fill up the infinite container supplied by ScrollView.

* The {@link TextView} class also

* takes care of its own scrolling, so does not require a ScrollView, but

* using the two together is possible to achieve the effect of a text view

* within a larger container.

* ScrollView only supports vertical scrolling. For horizontal scrolling,

* use {@link HorizontalScrollView}.

* @attr ref android.R.styleable#ScrollView_fillViewport

public class ScrollView extends FrameLayout {

public class NestedScrollView extends FrameLayout implements NestedScrollingParent3,

NestedScrollingChild3, ScrollingView {

static final int ANIMATED_SCROLL_GAP = 250;

static final float MAX_SCROLL_FACTOR = 0.5f;

private static final String TAG = "NestedScrollView";

private static final int DEFAULT_SMOOTH_SCROLL_DURATION = 250;

/**

* The following are copied from OverScroller to determine how far a fling will go.

private static final float SCROLL_FRICTION = 0.015f;

private static final float INFLEXION = 0.35f; // Tension lines cross at (INFLEXION, 1)

private static final float DECELERATION_RATE = (float) (Math.log(0.78) / Math.log(0.9));

private final float mPhysicalCoeff;

/**

* When flinging the stretch towards scrolling content, it should destretch quicker than the

* fling would normally do. The visual effect of flinging the stretch looks strange as little

* appears to happen at first and then when the stretch disappears, the content starts

* scrolling quickly.

private static final float FLING_DESTRETCH_FACTOR = 4f;

/**

* Interface definition for a callback to be invoked when the scroll

* X or Y positions of a view change.

* This version of the interface works on all versions of Android, back to API v4.

* @see #setOnScrollChangeListener(OnScrollChangeListener)

public interface OnScrollChangeListener {

/**

* Called when the scroll position of a view changes.

* @param v The view whose scroll position has changed.

* @param scrollX Current horizontal scroll origin.

* @param scrollY Current vertical scroll origin.

* @param oldScrollX Previous horizontal scroll origin.

* @param oldScrollY Previous vertical scroll origin.

void onScrollChange(@NonNull NestedScrollView v, int scrollX, int scrollY,

int oldScrollX, int oldScrollY);

}

private long mLastScroll;

private final Rect mTempRect = new Rect();

private OverScroller mScroller;

private EdgeEffect mEdgeGlowTop;

@RestrictTo(LIBRARY)

private EdgeEffect mEdgeGlowBottom;

@VisibleForTesting

@NonNull

public EdgeEffect mEdgeGlowTop;

@RestrictTo(LIBRARY)

@VisibleForTesting

@NonNull

public EdgeEffect mEdgeGlowBottom;

/**

* Position of the last motion event.

* Position of the last motion event; only used with touch related events (usually to assist

* in movement changes in a drag gesture).

private int mLastMotionY;

/**

* True when the layout has changed but the traversal has not come through yet.

* Ideally the view hierarchy would keep track of this for us.

private boolean mIsLayoutDirty = true;

private boolean mIsLaidOut = false;

/**

* The child to give focus to in the event that a child has requested focus while the

* layout is dirty. This prevents the scroll from being wrong if the child has not been

* laid out before requesting focus.

private View mChildToScrollTo = null;

/**

* True if the user is currently dragging this ScrollView around. This is

* not the same as 'is being flinged', which can be checked by

* mScroller.isFinished() (flinging begins when the user lifts his finger).

* mScroller.isFinished() (flinging begins when the user lifts their finger).

private boolean mIsBeingDragged = false;

/**

* Determines speed during touch scrolling

private VelocityTracker mVelocityTracker;

/**

* When set to true, the scroll view measure its child to make it fill the currently

* visible area.

@ViewDebug.ExportedProperty(category = "layout")

private boolean mFillViewport;

/**

* Whether arrow scrolling is animated.

private boolean mSmoothScrollingEnabled = true;

private int mTouchSlop;

private int mMinimumVelocity;

private int mMaximumVelocity;

private int mOverscrollDistance;

private int mOverflingDistance;

/**

* ID of the active pointer. This is used to retain consistency during

* drags/flings if multiple pointers are used.

private int mActivePointerId = INVALID_POINTER;

/**

* The StrictMode "critical time span" objects to catch animation

* Used during scrolling to retrieve the new offset within the window. Saves memory by saving

* stutters. Non-null when a time-sensitive animation is

* x, y changes to this array (0 position = x, 1 position = y) vs. reallocating an x and y

* in-flight. Must call finish() on them when done animating.

* every time.

* These are no-ops on user builds.

private StrictMode.Span mScrollStrictSpan = null; // aka "drag"

private final int[] mScrollOffset = new int[2];

private StrictMode.Span mFlingStrictSpan = null;

* Used during scrolling to retrieve the new consumed offset within the window.

* Uses same memory saving strategy as mScrollOffset.

private final int[] mScrollConsumed = new int[2];

// Used to track the position of the touch only events relative to the container.

private int mNestedYOffset;

private int mLastScrollerY;

/**

* Sentinel value for no current active pointer.

* Used by {@link #mActivePointerId}.

private static final int INVALID_POINTER = -1;

public ScrollView(Context context) {

private SavedState mSavedState;

private static final AccessibilityDelegate ACCESSIBILITY_DELEGATE = new AccessibilityDelegate();

private static final int[] SCROLLVIEW_STYLEABLE = new int[] {

android.R.attr.fillViewport

};

private final NestedScrollingParentHelper mParentHelper;

private final NestedScrollingChildHelper mChildHelper;

private float mVerticalScrollFactor;

private OnScrollChangeListener mOnScrollChangeListener;

@VisibleForTesting

final DifferentialMotionFlingTargetImpl mDifferentialMotionFlingTarget =

new DifferentialMotionFlingTargetImpl();

@VisibleForTesting

DifferentialMotionFlingController mDifferentialMotionFlingController =

new DifferentialMotionFlingController(getContext(), mDifferentialMotionFlingTarget);

public NestedScrollView(@NonNull Context context) {

this(context, null);

}

public ScrollView(Context context, AttributeSet attrs) {

public NestedScrollView(@NonNull Context context, @Nullable AttributeSet attrs) {

this(context, attrs, com.android.internal.R.attr.scrollViewStyle);

this(context, attrs, R.attr.nestedScrollViewStyle);

}

public ScrollView(Context context, AttributeSet attrs, int defStyle) {

public NestedScrollView(@NonNull Context context, @Nullable AttributeSet attrs,

super(context, attrs, defStyle);

int defStyleAttr) {

super(context, attrs, defStyleAttr);

mEdgeGlowTop = EdgeEffectCompat.create(context, attrs);

mEdgeGlowBottom = EdgeEffectCompat.create(context, attrs);

final float ppi = context.getResources().getDisplayMetrics().density * 160.0f;

mPhysicalCoeff = SensorManager.GRAVITY_EARTH // g (m/s^2)

* 39.37f // inch/meter

* ppi

* 0.84f; // look and feel tuning

initScrollView();

TypedArray a =

final TypedArray a = context.obtainStyledAttributes(

context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0);

attrs, SCROLLVIEW_STYLEABLE, defStyleAttr, 0);

setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false));

setFillViewport(a.getBoolean(0, false));

a.recycle();

mParentHelper = new NestedScrollingParentHelper(this);

mChildHelper = new NestedScrollingChildHelper(this);

// ...because why else would you be using this widget?

setNestedScrollingEnabled(true);

ViewCompat.setAccessibilityDelegate(this, ACCESSIBILITY_DELEGATE);

}

// NestedScrollingChild3

@Override

public void dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed,

int dyUnconsumed, @Nullable int[] offsetInWindow, int type, @NonNull int[] consumed) {

mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed,

offsetInWindow, type, consumed);

}

// NestedScrollingChild2

@Override

public boolean startNestedScroll(int axes, int type) {

return mChildHelper.startNestedScroll(axes, type);

}

@Override

public void stopNestedScroll(int type) {

mChildHelper.stopNestedScroll(type);

}

@Override

public boolean hasNestedScrollingParent(int type) {

return mChildHelper.hasNestedScrollingParent(type);

}

@Override

public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed,

int dyUnconsumed, @Nullable int[] offsetInWindow, int type) {

return mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed,

offsetInWindow, type);

}

@Override

public boolean dispatchNestedPreScroll(

int dx,

int dy,

@Nullable int[] consumed,

@Nullable int[] offsetInWindow,

int type

) {

return mChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type);

}

// NestedScrollingChild

@Override

public void setNestedScrollingEnabled(boolean enabled) {

mChildHelper.setNestedScrollingEnabled(enabled);

}

@Override

public boolean isNestedScrollingEnabled() {

return mChildHelper.isNestedScrollingEnabled();

}

@Override

public boolean startNestedScroll(int axes) {

return startNestedScroll(axes, ViewCompat.TYPE_TOUCH);

}

@Override

public void stopNestedScroll() {

stopNestedScroll(ViewCompat.TYPE_TOUCH);

}

@Override

public boolean hasNestedScrollingParent() {

return hasNestedScrollingParent(ViewCompat.TYPE_TOUCH);

}

@Override

public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed,

int dyUnconsumed, @Nullable int[] offsetInWindow) {

return mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed,

offsetInWindow);

}

@Override

public boolean dispatchNestedPreScroll(int dx, int dy, @Nullable int[] consumed,

@Nullable int[] offsetInWindow) {

return dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, ViewCompat.TYPE_TOUCH);

}

@Override

public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {

return mChildHelper.dispatchNestedFling(velocityX, velocityY, consumed);

}

@Override

public boolean dispatchNestedPreFling(float velocityX, float velocityY) {

return mChildHelper.dispatchNestedPreFling(velocityX, velocityY);

}

// NestedScrollingParent3

@Override

public void onNestedScroll(@NonNull View target, int dxConsumed, int dyConsumed,

int dxUnconsumed, int dyUnconsumed, int type, @NonNull int[] consumed) {

onNestedScrollInternal(dyUnconsumed, type, consumed);

}

private void onNestedScrollInternal(int dyUnconsumed, int type, @Nullable int[] consumed) {

final int oldScrollY = getScrollY();

scrollBy(0, dyUnconsumed);

final int myConsumed = getScrollY() - oldScrollY;

if (consumed != null) {

consumed[1] += myConsumed;

}

final int myUnconsumed = dyUnconsumed - myConsumed;

mChildHelper.dispatchNestedScroll(0, myConsumed, 0, myUnconsumed, null, type, consumed);

}

// NestedScrollingParent2

@Override

public boolean onStartNestedScroll(@NonNull View child, @NonNull View target, int axes,

int type) {

return (axes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0;

}

@Override

public void onNestedScrollAccepted(@NonNull View child, @NonNull View target, int axes,

int type) {

mParentHelper.onNestedScrollAccepted(child, target, axes, type);

startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL, type);

}

@Override

public void onStopNestedScroll(@NonNull View target, int type) {

mParentHelper.onStopNestedScroll(target, type);

stopNestedScroll(type);

}

@Override

public void onNestedScroll(@NonNull View target, int dxConsumed, int dyConsumed,

int dxUnconsumed, int dyUnconsumed, int type) {

onNestedScrollInternal(dyUnconsumed, type, null);

}

@Override

public void onNestedPreScroll(@NonNull View target, int dx, int dy, @NonNull int[] consumed,

int type) {

dispatchNestedPreScroll(dx, dy, consumed, null, type);

}

// NestedScrollingParent

@Override

public boolean onStartNestedScroll(

@NonNull View child, @NonNull View target, int axes) {

return onStartNestedScroll(child, target, axes, ViewCompat.TYPE_TOUCH);

}

@Override

public void onNestedScrollAccepted(

@NonNull View child, @NonNull View target, int axes) {

onNestedScrollAccepted(child, target, axes, ViewCompat.TYPE_TOUCH);

}

@Override

public void onStopNestedScroll(@NonNull View target) {

onStopNestedScroll(target, ViewCompat.TYPE_TOUCH);

}

@Override

public void onNestedScroll(@NonNull View target, int dxConsumed, int dyConsumed,

int dxUnconsumed, int dyUnconsumed) {

onNestedScrollInternal(dyUnconsumed, ViewCompat.TYPE_TOUCH, null);

}

@Override

public void onNestedPreScroll(@NonNull View target, int dx, int dy, @NonNull int[] consumed) {

onNestedPreScroll(target, dx, dy, consumed, ViewCompat.TYPE_TOUCH);

}

@Override

public boolean onNestedFling(

@NonNull View target, float velocityX, float velocityY, boolean consumed) {

if (!consumed) {

dispatchNestedFling(0, velocityY, true);

fling((int) velocityY);

return true;

Text moved from lines 354-356

}

return false;

}

@Override

public boolean onNestedPreFling(@NonNull View target, float velocityX, float velocityY) {

return dispatchNestedPreFling(velocityX, velocityY);

}

@Override

public int getNestedScrollAxes() {

return mParentHelper.getNestedScrollAxes();

}

// ScrollView import

@Override

public boolean shouldDelayChildPressedState() {

return true;

}

@Override

protected float getTopFadingEdgeStrength() {

if (getChildCount() == 0) {

return 0.0f;

}

final int length = getVerticalFadingEdgeLength();

if (mScrollY < length) {

final int scrollY = getScrollY();

return mScrollY / (float) length;

if (scrollY < length) {

return scrollY / (float) length;

}

return 1.0f;

}

@Override

protected float getBottomFadingEdgeStrength() {

if (getChildCount() == 0) {

return 0.0f;

}

View child = getChildAt(0);

final LayoutParams lp = (LayoutParams) child.getLayoutParams();

final int length = getVerticalFadingEdgeLength();

final int bottomEdge = getHeight() - mPaddingBottom;

final int bottomEdge = getHeight() - getPaddingBottom();

final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge;

final int span = child.getBottom() + lp.bottomMargin - getScrollY() - bottomEdge;

if (span < length) {

return span / (float) length;

}

return 1.0f;

}

/**

* @return The maximum amount this scroll view will scroll in response to

* an arrow event.

public int getMaxScrollAmount() {

return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop));

return (int) (MAX_SCROLL_FACTOR * getHeight());

}

private void initScrollView() {

mScroller = new OverScroller(getContext());

setFocusable(true);

setDescendantFocusability(FOCUS_AFTER_DESCENDANTS);

setWillNotDraw(false);

final ViewConfiguration configuration = ViewConfiguration.get(mContext);

final ViewConfiguration configuration = ViewConfiguration.get(getContext());

mTouchSlop = configuration.getScaledTouchSlop();

mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();

mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();

mOverscrollDistance = configuration.getScaledOverscrollDistance();

mOverflingDistance = configuration.getScaledOverflingDistance();

}

@Override

public void addView(View child) {

public void addView(@NonNull View child) {

if (getChildCount() > 0) {

throw new IllegalStateException("ScrollView can host only one direct child");

}

super.addView(child);

}

@Override

public void addView(View child, int index) {

if (getChildCount() > 0) {

throw new IllegalStateException("ScrollView can host only one direct child");

}

super.addView(child, index);

}

@Override

public void addView(View child, ViewGroup.LayoutParams params) {

if (getChildCount() > 0) {

throw new IllegalStateException("ScrollView can host only one direct child");

}

super.addView(child, params);

}

@Override

public void addView(View child, int index, ViewGroup.LayoutParams params) {

if (getChildCount() > 0) {

throw new IllegalStateException("ScrollView can host only one direct child");

}

super.addView(child, index, params);

}

/**

* Register a callback to be invoked when the scroll X or Y positions of

* this view change.

* This version of the method works on all versions of Android, back to API v4.

* @param l The listener to notify when the scroll X or Y position changes.

* @see View#getScrollX()

* @see View#getScrollY()

public void setOnScrollChangeListener(@Nullable OnScrollChangeListener l) {

mOnScrollChangeListener = l;

}

/**

* @return Returns true this ScrollView can be scrolled

private boolean canScroll() {

View child = getChildAt(0);

if (getChildCount() > 0) {

if (child != null) {

View child = getChildAt(0);

int childHeight = child.getHeight();

final LayoutParams lp = (LayoutParams) child.getLayoutParams();

return getHeight() < childHeight + mPaddingTop + mPaddingBottom;

int childSize = child.getHeight() + lp.topMargin + lp.bottomMargin;

int parentSpace = getHeight() - getPaddingTop() - getPaddingBottom();

return childSize > parentSpace;

}

return false;

}

/**

* Indicates whether this ScrollView's content is stretched to fill the viewport.

* @return True if the content fills the viewport, false otherwise.

* @attr ref android.R.styleable#ScrollView_fillViewport

* @attr name android:fillViewport

public boolean isFillViewport() {

return mFillViewport;

}

/**

* Indicates this ScrollView whether it should stretch its content height to fill

* Set whether this ScrollView should stretch its content height to fill the viewport or not.

* the viewport or not.

* @param fillViewport True to stretch the content's height to the viewport's

* boundaries, false otherwise.

* @attr ref android.R.styleable#ScrollView_fillViewport

* @attr name android:fillViewport

public void setFillViewport(boolean fillViewport) {

if (fillViewport != mFillViewport) {

mFillViewport = fillViewport;

requestLayout();

}

/**

* @return Whether arrow scrolling will animate its transition.

public boolean isSmoothScrollingEnabled() {

return mSmoothScrollingEnabled;

}

/**

* Set whether arrow scrolling will animate its transition.

* @param smoothScrollingEnabled whether arrow scrolling will animate its transition

public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) {

mSmoothScrollingEnabled = smoothScrollingEnabled;

}

@Override

protected void onScrollChanged(int l, int t, int oldl, int oldt) {

super.onScrollChanged(l, t, oldl, oldt);

if (mOnScrollChangeListener != null) {

mOnScrollChangeListener.onScrollChange(this, l, t, oldl, oldt);

Text moved from lines 373-375

}

@Override

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

super.onMeasure(widthMeasureSpec, heightMeasureSpec);

if (!mFillViewport) {

return;

}

final int heightMode = MeasureSpec.getMode(heightMeasureSpec);

if (heightMode == MeasureSpec.UNSPECIFIED) {

return;

}

if (getChildCount() > 0) {

final View child = getChildAt(0);

View child = getChildAt(0);

int height = getMeasuredHeight();

final LayoutParams lp = (LayoutParams) child.getLayoutParams();

if (child.getMeasuredHeight() < height) {

int childSize = child.getMeasuredHeight();

final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams();

int parentSpace = getMeasuredHeight()

- getPaddingTop()

- getPaddingBottom()

- lp.topMargin

- lp.bottomMargin;

if (childSize < parentSpace) {

int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec,

mPaddingLeft + mPaddingRight, lp.width);

getPaddingLeft() + getPaddingRight() + lp.leftMargin + lp.rightMargin,

height -= mPaddingTop;

lp.width);

height -= mPaddingBottom;

int childHeightMeasureSpec =

MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);

MeasureSpec.makeMeasureSpec(parentSpace, MeasureSpec.EXACTLY);

child.measure(childWidthMeasureSpec, childHeightMeasureSpec);

}

@Override

public boolean dispatchKeyEvent(KeyEvent event) {

// Let the focused view and/or our descendants get the key first

return super.dispatchKeyEvent(event) || executeKeyEvent(event);

}

/**

* You can call this function yourself to have the scroll view perform

* scrolling from a key event, just as if the event had been dispatched to

* it by the view hierarchy.

* @param event The key event to execute.

* @return Return true if the event was handled, else false.

public boolean executeKeyEvent(KeyEvent event) {

public boolean executeKeyEvent(@NonNull KeyEvent event) {

mTempRect.setEmpty();

if (!canScroll()) {

if (isFocused() && event.getKeyCode() != KeyEvent.KEYCODE_BACK) {

View currentFocused = findFocus();

if (currentFocused == this) currentFocused = null;

View nextFocused = FocusFinder.getInstance().findNextFocus(this,

currentFocused, View.FOCUS_DOWN);

return nextFocused != null

&& nextFocused != this

&& nextFocused.requestFocus(View.FOCUS_DOWN);

}

return false;

}

boolean handled = false;

if (event.getAction() == KeyEvent.ACTION_DOWN) {

switch (event.getKeyCode()) {

case KeyEvent.KEYCODE_DPAD_UP:

if (!event.isAltPressed()) {

if (event.isAltPressed()) {

handled = fullScroll(View.FOCUS_UP);

} else {

handled = arrowScroll(View.FOCUS_UP);

} else {

handled = fullScroll(View.FOCUS_UP);

}

break;

case KeyEvent.KEYCODE_DPAD_DOWN:

if (!event.isAltPressed()) {

if (event.isAltPressed()) {

handled = fullScroll(View.FOCUS_DOWN);

} else {

handled = arrowScroll(View.FOCUS_DOWN);

} else {

handled = fullScroll(View.FOCUS_DOWN);

}

break;

case KeyEvent.KEYCODE_SPACE:

pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN);

break;

}

return handled;

}

private boolean inChild(int x, int y) {

if (getChildCount() > 0) {

final int scrollY = mScrollY;

final View child = getChildAt(0);

return !(y < child.getTop() - scrollY

|| y >= child.getBottom() - scrollY

|| x < child.getLeft()

|| x >= child.getRight());

Text moved to lines 381-383

}

return false;

}

private void initOrResetVelocityTracker() {

if (mVelocityTracker == null) {

mVelocityTracker = VelocityTracker.obtain();

} else {

mVelocityTracker.clear();

}

private void initVelocityTrackerIfNotExists() {

if (mVelocityTracker == null) {

mVelocityTracker = VelocityTracker.obtain();

}

private void recycleVelocityTracker() {

if (mVelocityTracker != null) {

mVelocityTracker.recycle();

mVelocityTracker = null;

Text moved to lines 536-538

}

@Override

public void requestDisallowInterceptTouchEvent(boolean disallowIntercept) {

if (disallowIntercept) {

recycleVelocityTracker();

}

super.requestDisallowInterceptTouchEvent(disallowIntercept);

}

@Override

public boolean onInterceptTouchEvent(MotionEvent ev) {

* This method JUST determines whether we want to intercept the motion.

* If we return true, onMotionEvent will be called and we do the actual

* scrolling there.

* Shortcut the most recurring case: the user is in the dragging

* state and he is moving his finger. We want to intercept this

* motion.

final int action = ev.getAction();

if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) {

return true;

}

switch (action & MotionEvent.ACTION_MASK) {

case MotionEvent.ACTION_MOVE: {

* mIsBeingDragged == false, otherwise the shortcut would have caught it. Check

* whether the user has moved far enough from his original down touch.

* Locally do absolute value. mLastMotionY is set to the y value

* of the down event.

final int activePointerId = mActivePointerId;

if (activePointerId == INVALID_POINTER) {

// If we don't have a valid id, the touch down wasn't on content.

break;

}

final int pointerIndex = ev.findPointerIndex(activePointerId);

final int y = (int) ev.getY(pointerIndex);

final int yDiff = Math.abs(y - mLastMotionY);

if (yDiff > mTouchSlop) {

mIsBeingDragged = true;

mLastMotionY = y;

initVelocityTrackerIfNotExists();

mVelocityTracker.addMovement(ev);

if (mScrollStrictSpan == null) {

mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll");

}

final ViewParent parent = getParent();

if (parent != null) {

parent.requestDisallowInterceptTouchEvent(true);

}

break;

}

case MotionEvent.ACTION_DOWN: {

final int y = (int) ev.getY();

if (!inChild((int) ev.getX(), (int) y)) {

mIsBeingDragged = false;

recycleVelocityTracker();

break;

}

* Remember location of down touch.

* ACTION_DOWN always refers to pointer index 0.

mLastMotionY = y;

mActivePointerId = ev.getPointerId(0);

initOrResetVelocityTracker();

mVelocityTracker.addMovement(ev);

* If being flinged and user touches the screen, initiate drag;

* otherwise don't. mScroller.isFinished should be false when

* being flinged.

mIsBeingDragged = !mScroller.isFinished();

if (mIsBeingDragged && mScrollStrictSpan == null) {

mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll");

}

break;

}

case MotionEvent.ACTION_CANCEL:

case MotionEvent.ACTION_UP:

/* Release the drag */

mIsBeingDragged = false;

mActivePointerId = INVALID_POINTER;

recycleVelocityTracker();

if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) {

postInvalidateOnAnimation();

}

break;

case MotionEvent.ACTION_POINTER_UP:

onSecondaryPointerUp(ev);

break;

}

* The only time we want to intercept motion events is if we are in the

* drag mode.

return mIsBeingDragged;

}

@Override

public boolean onTouchEvent(MotionEvent ev) {

initVelocityTrackerIfNotExists();

mVelocityTracker.addMovement(ev);

final int action = ev.getAction();

switch (action & MotionEvent.ACTION_MASK) {

case MotionEvent.ACTION_DOWN: {

if (getChildCount() == 0) {

return false;

}

if ((mIsBeingDragged = !mScroller.isFinished())) {

final ViewParent parent = getParent();

if (parent != null) {

parent.requestDisallowInterceptTouchEvent(true);

}

* If being flinged and user touches, stop the fling. isFinished

* will be false if being flinged.

if (!mScroller.isFinished()) {

mScroller.abortAnimation();

if (mFlingStrictSpan != null) {

mFlingStrictSpan.finish();

mFlingStrictSpan = null;

}

// Remember where the motion event started

mLastMotionY = (int) ev.getY();

mActivePointerId = ev.getPointerId(0);

break;

}

case MotionEvent.ACTION_MOVE:

final int activePointerIndex = ev.findPointerIndex(mActivePointerId);

final int y = (int) ev.getY(activePointerIndex);

int deltaY = mLastMotionY - y;

if (!mIsBeingDragged && Math.abs(deltaY) > mTouchSlop) {

final ViewParent parent = getParent();

if (parent != null) {

parent.requestDisallowInterceptTouchEvent(true);

}

mIsBeingDragged = true;

if (deltaY > 0) {

deltaY -= mTouchSlop;

} else {

deltaY += mTouchSlop;

}

if (mIsBeingDragged) {

// Scroll to follow the motion event

mLastMotionY = y;

final int oldX = mScrollX;

final int oldY = mScrollY;

final int range = getScrollRange();

final int overscrollMode = getOverScrollMode();

final boolean canOverscroll = overscrollMode == OVER_SCROLL_ALWAYS ||

(overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0);

if (overScrollBy(0, deltaY, 0, mScrollY,

0, range, 0, mOverscrollDistance, true)) {

// Break our velocity if we hit a scroll barrier.

mVelocityTracker.clear();

}

onScrollChanged(mScrollX, mScrollY, oldX, oldY);

if (canOverscroll) {

final int pulledToY = oldY + deltaY;

if (pulledToY < 0) {

mEdgeGlowTop.onPull((float) deltaY / getHeight());

if (!mEdgeGlowBottom.isFinished()) {

mEdgeGlowBottom.onRelease();

}

} else if (pulledToY > range) {

mEdgeGlowBottom.onPull((float) deltaY / getHeight());

if (!mEdgeGlowTop.isFinished()) {

mEdgeGlowTop.onRelease();

}

if (mEdgeGlowTop != null

&& (!mEdgeGlowTop.isFinished() || !mEdgeGlowBottom.isFinished())) {

postInvalidateOnAnimation();

}

break;

case MotionEvent.ACTION_UP:

if (mIsBeingDragged) {

final VelocityTracker velocityTracker = mVelocityTracker;

velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);

int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId);

if (getChildCount() > 0) {

if ((Math.abs(initialVelocity) > mMinimumVelocity)) {

fling(-initialVelocity);

} else {

if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0,

getScrollRange())) {

postInvalidateOnAnimation();

}

mActivePointerId = INVALID_POINTER;

endDrag();

}

break;

case MotionEvent.ACTION_CANCEL:

if (mIsBeingDragged && getChildCount() > 0) {

if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) {

postInvalidateOnAnimation();

}

mActivePointerId = INVALID_POINTER;

endDrag();

}

break;

case MotionEvent.ACTION_POINTER_DOWN: {

final int index = ev.getActionIndex();

mLastMotionY = (int) ev.getY(index);

mActivePointerId = ev.getPointerId(index);

break;

}

case MotionEvent.ACTION_POINTER_UP:

onSecondaryPointerUp(ev);

mLastMotionY = (int) ev.getY(ev.findPointerIndex(mActivePointerId));

break;

}

return true;

}

private void onSecondaryPointerUp(MotionEvent ev) {

final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >>

MotionEvent.ACTION_POINTER_INDEX_SHIFT;

final int pointerId = ev.getPointerId(pointerIndex);

if (pointerId ==

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android / platform / frameworks / base / jb-release / . / core / java / android / widget / ScrollView.java
blob: ebc54f4527c8165cac4cc387d16b7f6d90bbf0e5 [file] [log] [blame]
/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package android.widget;
import com.android.internal.R;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.os.Bundle;
import android.os.StrictMode;
import android.util.AttributeSet;
import android.view.FocusFinder;
import android.view.InputDevice;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewDebug;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.view.accessibility.AccessibilityEvent;
import android.view.accessibility.AccessibilityNodeInfo;
import android.view.animation.AnimationUtils;
import java.util.List;
/**
 * Layout container for a view hierarchy that can be scrolled by the user,
 * allowing it to be larger than the physical display. A ScrollView
 * is a {@link FrameLayout}, meaning you should place one child in it
 * containing the entire contents to scroll; this child may itself be a layout
 * manager with a complex hierarchy of objects. A child that is often used
 * is a {@link LinearLayout} in a vertical orientation, presenting a vertical
 * array of top-level items that the user can scroll through.
 * You should never use a ScrollView with a {@link ListView}, because
 * ListView takes care of its own vertical scrolling. Most importantly, doing this
 * defeats all of the important optimizations in ListView for dealing with
 * large lists, since it effectively forces the ListView to display its entire
 * list of items to fill up the infinite container supplied by ScrollView.
 * The {@link TextView} class also
 * takes care of its own scrolling, so does not require a ScrollView, but
 * using the two together is possible to achieve the effect of a text view
 * within a larger container.
 *
 * ScrollView only supports vertical scrolling. For horizontal scrolling,
 * use {@link HorizontalScrollView}.
 *
 * @attr ref android.R.styleable#ScrollView_fillViewport
 */
public class ScrollView extends FrameLayout {
 static final int ANIMATED_SCROLL_GAP = 250;
 static final float MAX_SCROLL_FACTOR = 0.5f;
 private long mLastScroll;
 private final Rect mTempRect = new Rect();
 private OverScroller mScroller;
 private EdgeEffect mEdgeGlowTop;
 private EdgeEffect mEdgeGlowBottom;
 /**
 * Position of the last motion event.
 */
 private int mLastMotionY;
 /**
 * True when the layout has changed but the traversal has not come through yet.
 * Ideally the view hierarchy would keep track of this for us.
 */
 private boolean mIsLayoutDirty = true;
 /**
 * The child to give focus to in the event that a child has requested focus while the
 * layout is dirty. This prevents the scroll from being wrong if the child has not been
 * laid out before requesting focus.
 */
 private View mChildToScrollTo = null;
 /**
 * True if the user is currently dragging this ScrollView around. This is
 * not the same as 'is being flinged', which can be checked by
 * mScroller.isFinished() (flinging begins when the user lifts his finger).
 */
 private boolean mIsBeingDragged = false;
 /**
 * Determines speed during touch scrolling
 */
 private VelocityTracker mVelocityTracker;
 /**
 * When set to true, the scroll view measure its child to make it fill the currently
 * visible area.
 */
 @ViewDebug.ExportedProperty(category = "layout")
 private boolean mFillViewport;
 /**
 * Whether arrow scrolling is animated.
 */
 private boolean mSmoothScrollingEnabled = true;
 private int mTouchSlop;
 private int mMinimumVelocity;
 private int mMaximumVelocity;
 private int mOverscrollDistance;
 private int mOverflingDistance;
 /**
 * ID of the active pointer. This is used to retain consistency during
 * drags/flings if multiple pointers are used.
 */
 private int mActivePointerId = INVALID_POINTER;
 /**
 * The StrictMode "critical time span" objects to catch animation
 * stutters. Non-null when a time-sensitive animation is
 * in-flight. Must call finish() on them when done animating.
 * These are no-ops on user builds.
 */
 private StrictMode.Span mScrollStrictSpan = null; // aka "drag"
 private StrictMode.Span mFlingStrictSpan = null;
 /**
 * Sentinel value for no current active pointer.
 * Used by {@link #mActivePointerId}.
 */
 private static final int INVALID_POINTER = -1;
 public ScrollView(Context context) {
 this(context, null);
 }
 public ScrollView(Context context, AttributeSet attrs) {
 this(context, attrs, com.android.internal.R.attr.scrollViewStyle);
 }
 public ScrollView(Context context, AttributeSet attrs, int defStyle) {
 super(context, attrs, defStyle);
 initScrollView();
 TypedArray a =
 context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0);
 setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false));
 a.recycle();
 }
 @Override
 public boolean shouldDelayChildPressedState() {
 return true;
 }
 @Override
 protected float getTopFadingEdgeStrength() {
 if (getChildCount() == 0) {
 return 0.0f;
 }
 final int length = getVerticalFadingEdgeLength();
 if (mScrollY < length) {
 return mScrollY / (float) length;
 }
 return 1.0f;
 }
 @Override
 protected float getBottomFadingEdgeStrength() {
 if (getChildCount() == 0) {
 return 0.0f;
 }
 final int length = getVerticalFadingEdgeLength();
 final int bottomEdge = getHeight() - mPaddingBottom;
 final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge;
 if (span < length) {
 return span / (float) length;
 }
 return 1.0f;
 }
 /**
 * @return The maximum amount this scroll view will scroll in response to
 * an arrow event.
 */
 public int getMaxScrollAmount() {
 return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop));
 }
 private void initScrollView() {
 mScroller = new OverScroller(getContext());
 setFocusable(true);
 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS);
 setWillNotDraw(false);
 final ViewConfiguration configuration = ViewConfiguration.get(mContext);
 mTouchSlop = configuration.getScaledTouchSlop();
 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();
 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
 mOverscrollDistance = configuration.getScaledOverscrollDistance();
 mOverflingDistance = configuration.getScaledOverflingDistance();
 }
 @Override
 public void addView(View child) {
 if (getChildCount() > 0) {
 throw new IllegalStateException("ScrollView can host only one direct child");
 }
 super.addView(child);
 }
 @Override
 public void addView(View child, int index) {
 if (getChildCount() > 0) {
 throw new IllegalStateException("ScrollView can host only one direct child");
 }
 super.addView(child, index);
 }
 @Override
 public void addView(View child, ViewGroup.LayoutParams params) {
 if (getChildCount() > 0) {
 throw new IllegalStateException("ScrollView can host only one direct child");
 }
 super.addView(child, params);
 }
 @Override
 public void addView(View child, int index, ViewGroup.LayoutParams params) {
 if (getChildCount() > 0) {
 throw new IllegalStateException("ScrollView can host only one direct child");
 }
 super.addView(child, index, params);
 }
 /**
 * @return Returns true this ScrollView can be scrolled
 */
 private boolean canScroll() {
 View child = getChildAt(0);
 if (child != null) {
 int childHeight = child.getHeight();
 return getHeight() < childHeight + mPaddingTop + mPaddingBottom;
 }
 return false;
 }
 /**
 * Indicates whether this ScrollView's content is stretched to fill the viewport.
 *
 * @return True if the content fills the viewport, false otherwise.
 *
 * @attr ref android.R.styleable#ScrollView_fillViewport
 */
 public boolean isFillViewport() {
 return mFillViewport;
 }
 /**
 * Indicates this ScrollView whether it should stretch its content height to fill
 * the viewport or not.
 *
 * @param fillViewport True to stretch the content's height to the viewport's
 * boundaries, false otherwise.
 *
 * @attr ref android.R.styleable#ScrollView_fillViewport
 */
 public void setFillViewport(boolean fillViewport) {
 if (fillViewport != mFillViewport) {
 mFillViewport = fillViewport;
 requestLayout();
 }
 }
 /**
 * @return Whether arrow scrolling will animate its transition.
 */
 public boolean isSmoothScrollingEnabled() {
 return mSmoothScrollingEnabled;
 }
 /**
 * Set whether arrow scrolling will animate its transition.
 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition
 */
 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) {
 mSmoothScrollingEnabled = smoothScrollingEnabled;
 }
 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
 super.onMeasure(widthMeasureSpec, heightMeasureSpec);
 if (!mFillViewport) {
 return;
 }
 final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
 if (heightMode == MeasureSpec.UNSPECIFIED) {
 return;
 }
 if (getChildCount() > 0) {
 final View child = getChildAt(0);
 int height = getMeasuredHeight();
 if (child.getMeasuredHeight() < height) {
 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams();
 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec,
 mPaddingLeft + mPaddingRight, lp.width);
 height -= mPaddingTop;
 height -= mPaddingBottom;
 int childHeightMeasureSpec =
 MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);
 child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
 }
 }
 }
 @Override
 public boolean dispatchKeyEvent(KeyEvent event) {
 // Let the focused view and/or our descendants get the key first
 return super.dispatchKeyEvent(event) || executeKeyEvent(event);
 }
 /**
 * You can call this function yourself to have the scroll view perform
 * scrolling from a key event, just as if the event had been dispatched to
 * it by the view hierarchy.
 *
 * @param event The key event to execute.
 * @return Return true if the event was handled, else false.
 */
 public boolean executeKeyEvent(KeyEvent event) {
 mTempRect.setEmpty();
 if (!canScroll()) {
 if (isFocused() && event.getKeyCode() != KeyEvent.KEYCODE_BACK) {
 View currentFocused = findFocus();
 if (currentFocused == this) currentFocused = null;
 View nextFocused = FocusFinder.getInstance().findNextFocus(this,
 currentFocused, View.FOCUS_DOWN);
 return nextFocused != null
 && nextFocused != this
 && nextFocused.requestFocus(View.FOCUS_DOWN);
 }
 return false;
 }
 boolean handled = false;
 if (event.getAction() == KeyEvent.ACTION_DOWN) {
 switch (event.getKeyCode()) {
 case KeyEvent.KEYCODE_DPAD_UP:
 if (!event.isAltPressed()) {
 handled = arrowScroll(View.FOCUS_UP);
 } else {
 handled = fullScroll(View.FOCUS_UP);
 }
 break;
 case KeyEvent.KEYCODE_DPAD_DOWN:
 if (!event.isAltPressed()) {
 handled = arrowScroll(View.FOCUS_DOWN);
 } else {
 handled = fullScroll(View.FOCUS_DOWN);
 }
 break;
 case KeyEvent.KEYCODE_SPACE:
 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN);
 break;
 }
 }
 return handled;
 }
 private boolean inChild(int x, int y) {
 if (getChildCount() > 0) {
 final int scrollY = mScrollY;
 final View child = getChildAt(0);
 return !(y < child.getTop() - scrollY
 || y >= child.getBottom() - scrollY
 || x < child.getLeft()
 || x >= child.getRight());
 }
 return false;
 }
 private void initOrResetVelocityTracker() {
 if (mVelocityTracker == null) {
 mVelocityTracker = VelocityTracker.obtain();
 } else {
 mVelocityTracker.clear();
 }
 }
 private void initVelocityTrackerIfNotExists() {
 if (mVelocityTracker == null) {
 mVelocityTracker = VelocityTracker.obtain();
 }
 }
 private void recycleVelocityTracker() {
 if (mVelocityTracker != null) {
 mVelocityTracker.recycle();
 mVelocityTracker = null;
 }
 }
 @Override
 public void requestDisallowInterceptTouchEvent(boolean disallowIntercept) {
 if (disallowIntercept) {
 recycleVelocityTracker();
 }
 super.requestDisallowInterceptTouchEvent(disallowIntercept);
 }
 @Override
 public boolean onInterceptTouchEvent(MotionEvent ev) {
 /*
 * This method JUST determines whether we want to intercept the motion.
 * If we return true, onMotionEvent will be called and we do the actual
 * scrolling there.
 */
 /*
 * Shortcut the most recurring case: the user is in the dragging
 * state and he is moving his finger. We want to intercept this
 * motion.
 */
 final int action = ev.getAction();
 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) {
 return true;
 }
 switch (action & MotionEvent.ACTION_MASK) {
 case MotionEvent.ACTION_MOVE: {
 /*
 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check
 * whether the user has moved far enough from his original down touch.
 */
 /*
 * Locally do absolute value. mLastMotionY is set to the y value
 * of the down event.
 */
 final int activePointerId = mActivePointerId;
 if (activePointerId == INVALID_POINTER) {
 // If we don't have a valid id, the touch down wasn't on content.
 break;
 }
 final int pointerIndex = ev.findPointerIndex(activePointerId);
 final int y = (int) ev.getY(pointerIndex);
 final int yDiff = Math.abs(y - mLastMotionY);
 if (yDiff > mTouchSlop) {
 mIsBeingDragged = true;
 mLastMotionY = y;
 initVelocityTrackerIfNotExists();
 mVelocityTracker.addMovement(ev);
 if (mScrollStrictSpan == null) {
 mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll");
 }
 final ViewParent parent = getParent();
 if (parent != null) {
 parent.requestDisallowInterceptTouchEvent(true);
 }
 }
 break;
 }
 case MotionEvent.ACTION_DOWN: {
 final int y = (int) ev.getY();
 if (!inChild((int) ev.getX(), (int) y)) {
 mIsBeingDragged = false;
 recycleVelocityTracker();
 break;
 }
 /*
 * Remember location of down touch.
 * ACTION_DOWN always refers to pointer index 0.
 */
 mLastMotionY = y;
 mActivePointerId = ev.getPointerId(0);
 initOrResetVelocityTracker();
 mVelocityTracker.addMovement(ev);
 /*
 * If being flinged and user touches the screen, initiate drag;
 * otherwise don't. mScroller.isFinished should be false when
 * being flinged.
 */
 mIsBeingDragged = !mScroller.isFinished();
 if (mIsBeingDragged && mScrollStrictSpan == null) {
 mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll");
 }
 break;
 }
 case MotionEvent.ACTION_CANCEL:
 case MotionEvent.ACTION_UP:
 /* Release the drag */
 mIsBeingDragged = false;
 mActivePointerId = INVALID_POINTER;
 recycleVelocityTracker();
 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) {
 postInvalidateOnAnimation();
 }
 break;
 case MotionEvent.ACTION_POINTER_UP:
 onSecondaryPointerUp(ev);
 break;
 }
 /*
 * The only time we want to intercept motion events is if we are in the
 * drag mode.
 */
 return mIsBeingDragged;
 }
 @Override
 public boolean onTouchEvent(MotionEvent ev) {
 initVelocityTrackerIfNotExists();
 mVelocityTracker.addMovement(ev);
 final int action = ev.getAction();
 switch (action & MotionEvent.ACTION_MASK) {
 case MotionEvent.ACTION_DOWN: {
 if (getChildCount() == 0) {
 return false;
 }
 if ((mIsBeingDragged = !mScroller.isFinished())) {
 final ViewParent parent = getParent();
 if (parent != null) {
 parent.requestDisallowInterceptTouchEvent(true);
 }
 }
 /*
 * If being flinged and user touches, stop the fling. isFinished
 * will be false if being flinged.
 */
 if (!mScroller.isFinished()) {
 mScroller.abortAnimation();
 if (mFlingStrictSpan != null) {
 mFlingStrictSpan.finish();
 mFlingStrictSpan = null;
 }
 }
 // Remember where the motion event started
 mLastMotionY = (int) ev.getY();
 mActivePointerId = ev.getPointerId(0);
 break;
 }
 case MotionEvent.ACTION_MOVE:
 final int activePointerIndex = ev.findPointerIndex(mActivePointerId);
 final int y = (int) ev.getY(activePointerIndex);
 int deltaY = mLastMotionY - y;
 if (!mIsBeingDragged && Math.abs(deltaY) > mTouchSlop) {
 final ViewParent parent = getParent();
 if (parent != null) {
 parent.requestDisallowInterceptTouchEvent(true);
 }
 mIsBeingDragged = true;
 if (deltaY > 0) {
 deltaY -= mTouchSlop;
 } else {
 deltaY += mTouchSlop;
 }
 }
 if (mIsBeingDragged) {
 // Scroll to follow the motion event
 mLastMotionY = y;
 final int oldX = mScrollX;
 final int oldY = mScrollY;
 final int range = getScrollRange();
 final int overscrollMode = getOverScrollMode();
 final boolean canOverscroll = overscrollMode == OVER_SCROLL_ALWAYS ||
 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0);
 if (overScrollBy(0, deltaY, 0, mScrollY,
 0, range, 0, mOverscrollDistance, true)) {
 // Break our velocity if we hit a scroll barrier.
 mVelocityTracker.clear();
 }
 onScrollChanged(mScrollX, mScrollY, oldX, oldY);
 if (canOverscroll) {
 final int pulledToY = oldY + deltaY;
 if (pulledToY < 0) {
 mEdgeGlowTop.onPull((float) deltaY / getHeight());
 if (!mEdgeGlowBottom.isFinished()) {
 mEdgeGlowBottom.onRelease();
 }
 } else if (pulledToY > range) {
 mEdgeGlowBottom.onPull((float) deltaY / getHeight());
 if (!mEdgeGlowTop.isFinished()) {
 mEdgeGlowTop.onRelease();
 }
 }
 if (mEdgeGlowTop != null
 && (!mEdgeGlowTop.isFinished() || !mEdgeGlowBottom.isFinished())) {
 postInvalidateOnAnimation();
 }
 }
 }
 break;
 case MotionEvent.ACTION_UP:
 if (mIsBeingDragged) {
 final VelocityTracker velocityTracker = mVelocityTracker;
 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
 int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId);
 if (getChildCount() > 0) {
 if ((Math.abs(initialVelocity) > mMinimumVelocity)) {
 fling(-initialVelocity);
 } else {
 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0,
 getScrollRange())) {
 postInvalidateOnAnimation();
 }
 }
 }
 mActivePointerId = INVALID_POINTER;
 endDrag();
 }
 break;
 case MotionEvent.ACTION_CANCEL:
 if (mIsBeingDragged && getChildCount() > 0) {
 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) {
 postInvalidateOnAnimation();
 }
 mActivePointerId = INVALID_POINTER;
 endDrag();
 }
 break;
 case MotionEvent.ACTION_POINTER_DOWN: {
 final int index = ev.getActionIndex();
 mLastMotionY = (int) ev.getY(index);
 mActivePointerId = ev.getPointerId(index);
 break;
 }
 case MotionEvent.ACTION_POINTER_UP:
 onSecondaryPointerUp(ev);
 mLastMotionY = (int) ev.getY(ev.findPointerIndex(mActivePointerId));
 break;
 }
 return true;
 }
 private void onSecondaryPointerUp(MotionEvent ev) {
 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >>
 MotionEvent.ACTION_POINTER_INDEX_SHIFT;
 final int pointerId = ev.getPointerId(pointerIndex);
 if (pointerId == mActivePointerId) {
 // This was our active pointer going up. Choose a new
 // active pointer and adjust accordingly.
 // TODO: Make this decision more intelligent.
 final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
 mLastMotionY = (int) ev.getY(newPointerIndex);
 mActivePointerId = ev.getPointerId(newPointerIndex);
 if (mVelocityTracker != null) {
 mVelocityTracker.clear();
 }
 }
 }
 @Override
 public boolean onGenericMotionEvent(MotionEvent event) {
 if ((event.getSource() & InputDevice.SOURCE_CLASS_POINTER) != 0) {
 switch (event.getAction()) {
 case MotionEvent.ACTION_SCROLL: {
 if (!mIsBeingDragged) {
 final float vscroll = event.getAxisValue(MotionEvent.AXIS_VSCROLL);
 if (vscroll != 0) {
 final int delta = (int) (vscroll * getVerticalScrollFactor());
 final int range = getScrollRange();
 int oldScrollY = mScrollY;
 int newScrollY = oldScrollY - delta;
 if (newScrollY < 0) {
 newScrollY = 0;
 } else if (newScrollY > range) {
 newScrollY = range;
 }
 if (newScrollY != oldScrollY) {
 super.scrollTo(mScrollX, newScrollY);
 return true;
 }
 }
 }
 }
 }
 }
 return super.onGenericMotionEvent(event);
 }
 @Override
 protected void onOverScrolled(int scrollX, int scrollY,
 boolean clampedX, boolean clampedY) {
 // Treat animating scrolls differently; see #computeScroll() for why.
 if (!mScroller.isFinished()) {
 mScrollX = scrollX;
 mScrollY = scrollY;
 invalidateParentIfNeeded();
 if (clampedY) {
 mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange());
 }
 } else {
 super.scrollTo(scrollX, scrollY);
 }
 awakenScrollBars();
 }
 @Override
 public boolean performAccessibilityAction(int action, Bundle arguments) {
 if (super.performAccessibilityAction(action, arguments)) {
 return true;
 }
 if (!isEnabled()) {
 return false;
 }
 switch (action) {
 case AccessibilityNodeInfo.ACTION_SCROLL_FORWARD: {
 final int viewportHeight = getHeight() - mPaddingBottom - mPaddingTop;
 final int targetScrollY = Math.min(mScrollY + viewportHeight, getScrollRange());
 if (targetScrollY != mScrollY) {
 smoothScrollTo(0, targetScrollY);
 return true;
 }
 } return false;
 case AccessibilityNodeInfo.ACTION_SCROLL_BACKWARD: {
 final int viewportHeight = getHeight() - mPaddingBottom - mPaddingTop;
 final int targetScrollY = Math.max(mScrollY - viewportHeight, 0);
 if (targetScrollY != mScrollY) {
 smoothScrollTo(0, targetScrollY);
 return true;
 }
 } return false;
 }
 return false;
 }
 @Override
 public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) {
 super.onInitializeAccessibilityNodeInfo(info);
 info.setClassName(ScrollView.class.getName());
 if (isEnabled()) {
 final int scrollRange = getScrollRange();
 if (scrollRange > 0) {
 info.setScrollable(true);
 if (mScrollY > 0) {
 info.addAction(AccessibilityNodeInfo.ACTION_SCROLL_BACKWARD);
 }
 if (mScrollY < scrollRange) {
 info.addAction(AccessibilityNodeInfo.ACTION_SCROLL_FORWARD);
 }
 }
 }
 }
 @Override
 public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
 super.onInitializeAccessibilityEvent(event);
 event.setClassName(ScrollView.class.getName());
 final boolean scrollable = getScrollRange() > 0;
 event.setScrollable(scrollable);
 event.setScrollX(mScrollX);
 event.setScrollY(mScrollY);
 event.setMaxScrollX(mScrollX);
 event.setMaxScrollY(getScrollRange());
 }
 private int getScrollRange() {
 int scrollRange = 0;
 if (getChildCount() > 0) {
 View child = getChildAt(0);
 scrollRange = Math.max(0,
 child.getHeight() - (getHeight() - mPaddingBottom - mPaddingTop));
 }
 return scrollRange;
 }
 /**
 * 
 * Finds the next focusable component that fits in the specified bounds.
 * 
 *
 * @param topFocus look for a candidate is the one at the top of the bounds
 * if topFocus is true, or at the bottom of the bounds if topFocus is
 * false
 * @param top the top offset of the bounds in which a focusable must be
 * found
 * @param bottom the bottom offset of the bounds in which a focusable must
 * be found
 * @return the next focusable component in the bounds or null if none can
 * be found
 */
 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) {
 List<View> focusables = getFocusables(View.FOCUS_FORWARD);
 View focusCandidate = null;
 /*
 * A fully contained focusable is one where its top is below the bound's
 * top, and its bottom is above the bound's bottom. A partially
 * contained focusable is one where some part of it is within the
 * bounds, but it also has some part that is not within bounds. A fully contained
 * focusable is preferred to a partially contained focusable.
 */
 boolean foundFullyContainedFocusable = false;
 int count = focusables.size();
 for (int i = 0; i < count; i++) {
 View view = focusables.get(i);
 int viewTop = view.getTop();
 int viewBottom = view.getBottom();
 if (top < viewBottom && viewTop < bottom) {
 /*
 * the focusable is in the target area, it is a candidate for
 * focusing
 */
 final boolean viewIsFullyContained = (top < viewTop) &&
 (viewBottom < bottom);
 if (focusCandidate == null) {
 /* No candidate, take this one */
 focusCandidate = view;
 foundFullyContainedFocusable = viewIsFullyContained;
 } else {
 final boolean viewIsCloserToBoundary =
 (topFocus && viewTop < focusCandidate.getTop()) ||
 (!topFocus && viewBottom > focusCandidate
 .getBottom());
 if (foundFullyContainedFocusable) {
 if (viewIsFullyContained && viewIsCloserToBoundary) {
 /*
 * We're dealing with only fully contained views, so
 * it has to be closer to the boundary to beat our
 * candidate
 */
 focusCandidate = view;
 }
 } else {
 if (viewIsFullyContained) {
 /* Any fully contained view beats a partially contained view */
 focusCandidate = view;
 foundFullyContainedFocusable = true;
 } else if (viewIsCloserToBoundary) {
 /*
 * Partially contained view beats another partially
 * contained view if it's closer
 */
 focusCandidate = view;
 }
 }
 }
 }
 }
 return focusCandidate;
 }
 /**
 * Handles scrolling in response to a "page up/down" shortcut press. This
 * method will scroll the view by one page up or down and give the focus
 * to the topmost/bottommost component in the new visible area. If no
 * component is a good candidate for focus, this scrollview reclaims the
 * focus.
 *
 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP}
 * to go one page up or
 * {@link android.view.View#FOCUS_DOWN} to go one page down
 * @return true if the key event is consumed by this method, false otherwise
 */
 public boolean pageScroll(int direction) {
 boolean down = direction == View.FOCUS_DOWN;
 int height = getHeight();
 if (down) {
 mTempRect.top = getScrollY() + height;
 int count = getChildCount();
 if (count > 0) {
 View view = getChildAt(count - 1);
 if (mTempRect.top + height > view.getBottom()) {
 mTempRect.top = view.getBottom() - height;
 }
 }
 } else {
 mTempRect.top = getScrollY() - height;
 if (mTempRect.top < 0) {
 mTempRect.top = 0;
 }
 }
 mTempRect.bottom = mTempRect.top + height;
 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom);
 }
 /**
 * Handles scrolling in response to a "home/end" shortcut press. This
 * method will scroll the view to the top or bottom and give the focus
 * to the topmost/bottommost component in the new visible area. If no
 * component is a good candidate for focus, this scrollview reclaims the
 * focus.
 *
 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP}
 * to go the top of the view or
 * {@link android.view.View#FOCUS_DOWN} to go the bottom
 * @return true if the key event is consumed by this method, false otherwise
 */
 public boolean fullScroll(int direction) {
 boolean down = direction == View.FOCUS_DOWN;
 int height = getHeight();
 mTempRect.top = 0;
 mTempRect.bottom = height;
 if (down) {
 int count = getChildCount();
 if (count > 0) {
 View view = getChildAt(count - 1);
 mTempRect.bottom = view.getBottom() + mPaddingBottom;
 mTempRect.top = mTempRect.bottom - height;
 }
 }
 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom);
 }
 /**
 * Scrolls the view to make the area defined by <code>top</code> and
 * <code>bottom</code> visible. This method attempts to give the focus
 * to a component visible in this area. If no component can be focused in
 * the new visible area, the focus is reclaimed by this ScrollView.
 *
 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP}
 * to go upward, {@link android.view.View#FOCUS_DOWN} to downward
 * @param top the top offset of the new area to be made visible
 * @param bottom the bottom offset of the new area to be made visible
 * @return true if the key event is consumed by this method, false otherwise
 */
 private boolean scrollAndFocus(int direction, int top, int bottom) {
 boolean handled = true;
 int height = getHeight();
 int containerTop = getScrollY();
 int containerBottom = containerTop + height;
 boolean up = direction == View.FOCUS_UP;
 View newFocused = findFocusableViewInBounds(up, top, bottom);
 if (newFocused == null) {
 newFocused = this;
 }
 if (top >= containerTop && bottom <= containerBottom) {
 handled = false;
 } else {
 int delta = up ? (top - containerTop) : (bottom - containerBottom);
 doScrollY(delta);
 }
 if (newFocused != findFocus()) newFocused.requestFocus(direction);
 return handled;
 }
 /**
 * Handle scrolling in response to an up or down arrow click.
 *
 * @param direction The direction corresponding to the arrow key that was
 * pressed
 * @return True if we consumed the event, false otherwise
 */
 public boolean arrowScroll(int direction) {
 View currentFocused = findFocus();
 if (currentFocused == this) currentFocused = null;
 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction);
 final int maxJump = getMaxScrollAmount();
 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) {
 nextFocused.getDrawingRect(mTempRect);
 offsetDescendantRectToMyCoords(nextFocused, mTempRect);
 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect);
 doScrollY(scrollDelta);
 nextFocused.requestFocus(direction);
 } else {
 // no new focus
 int scrollDelta = maxJump;
 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) {
 scrollDelta = getScrollY();
 } else if (direction == View.FOCUS_DOWN) {
 if (getChildCount() > 0) {
 int daBottom = getChildAt(0).getBottom();
 int screenBottom = getScrollY() + getHeight() - mPaddingBottom;
 if (daBottom - screenBottom < maxJump) {
 scrollDelta = daBottom - screenBottom;
 }
 }
 }
 if (scrollDelta == 0) {
 return false;
 }
 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta);
 }
 if (currentFocused != null && currentFocused.isFocused()
 && isOffScreen(currentFocused)) {
 // previously focused item still has focus and is off screen, give
 // it up (take it back to ourselves)
 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are
 // sure to
 // get it)
 final int descendantFocusability = getDescendantFocusability(); // save
 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS);
 requestFocus();
 setDescendantFocusability(descendantFocusability); // restore
 }
 return true;
 }
 /**
 * @return whether the descendant of this scroll view is scrolled off
 * screen.
 */
 private boolean isOffScreen(View descendant) {
 return !isWithinDeltaOfScreen(descendant, 0, getHeight());
 }
 /**
 * @return whether the descendant of this scroll view is within delta
 * pixels of being on the screen.
 */
 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) {
 descendant.getDrawingRect(mTempRect);
 offsetDescendantRectToMyCoords(descendant, mTempRect);
 return (mTempRect.bottom + delta) >= getScrollY()
 && (mTempRect.top - delta) <= (getScrollY() + height);
 }
 /**
 * Smooth scroll by a Y delta
 *
 * @param delta the number of pixels to scroll by on the Y axis
 */
 private void doScrollY(int delta) {
 if (delta != 0) {
 if (mSmoothScrollingEnabled) {
 smoothScrollBy(0, delta);
 } else {
 scrollBy(0, delta);
 }
 }
 }
 /**
 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately.
 *
 * @param dx the number of pixels to scroll by on the X axis
 * @param dy the number of pixels to scroll by on the Y axis
 */
 public final void smoothScrollBy(int dx, int dy) {
 if (getChildCount() == 0) {
 // Nothing to do.
 return;
 }
 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll;
 if (duration > ANIMATED_SCROLL_GAP) {
 final int height = getHeight() - mPaddingBottom - mPaddingTop;
 final int bottom = getChildAt(0).getHeight();
 final int maxY = Math.max(0, bottom - height);
 final int scrollY = mScrollY;
 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY;
 mScroller.startScroll(mScrollX, scrollY, 0, dy);
 postInvalidateOnAnimation();
 } else {
 if (!mScroller.isFinished()) {
 mScroller.abortAnimation();
 if (mFlingStrictSpan != null) {
 mFlingStrictSpan.finish();
 mFlingStrictSpan = null;
 }
 }
 scrollBy(dx, dy);
 }
 mLastScroll = AnimationUtils.currentAnimationTimeMillis();
 }
 /**
 * Like {@link #scrollTo}, but scroll smoothly instead of immediately.
 *
 * @param x the position where to scroll on the X axis
 * @param y the position where to scroll on the Y axis
 */
 public final void smoothScrollTo(int x, int y) {
 smoothScrollBy(x - mScrollX, y - mScrollY);
 }
 /**
 * The scroll range of a scroll view is the overall height of all of its
 * children.
 */
 @Override
 protected int computeVerticalScrollRange() {
 final int count = getChildCount();
 final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop;
 if (count == 0) {
 return contentHeight;
 }
 int scrollRange = getChildAt(0).getBottom();
 final int scrollY = mScrollY;
 final int overscrollBottom = Math.max(0, scrollRange - contentHeight);
 if (scrollY < 0) {
 scrollRange -= scrollY;
 } else if (scrollY > overscrollBottom) {
 scrollRange += scrollY - overscrollBottom;
 }
 return scrollRange;
 }
 @Override
 protected int computeVerticalScrollOffset() {
 return Math.max(0, super.computeVerticalScrollOffset());
 }
 @Override
 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) {
 ViewGroup.LayoutParams lp = child.getLayoutParams();
 int childWidthMeasureSpec;
 int childHeightMeasureSpec;
 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft
 + mPaddingRight, lp.width);
 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
 child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
 }
 @Override
 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed,
 int parentHeightMeasureSpec, int heightUsed) {
 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec,
 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin
 + widthUsed, lp.width);
 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(
 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED);
 child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
 }
 @Override
 public void computeScroll() {
 if (mScroller.computeScrollOffset()) {
 // This is called at drawing time by ViewGroup. We don't want to
 // re-show the scrollbars at this point, which scrollTo will do,
 // so we replicate most of scrollTo here.
 //
 // It's a little odd to call onScrollChanged from inside the drawing.
 //
 // It is, except when you remember that computeScroll() is used to
 // animate scrolling. So unless we want to defer the onScrollChanged()
 // until the end of the animated scrolling, we don't really have a
 // choice here.
 //
 // I agree. The alternative, which I think would be worse, is to post
 // something and tell the subclasses later. This is bad because there
 // will be a window where mScrollX/Y is different from what the app
 // thinks it is.
 //
 int oldX = mScrollX;
 int oldY = mScrollY;
 int x = mScroller.getCurrX();
 int y = mScroller.getCurrY();
 if (oldX != x || oldY != y) {
 final int range = getScrollRange();
 final int overscrollMode = getOverScrollMode();
 final boolean canOverscroll = overscrollMode == OVER_SCROLL_ALWAYS ||
 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0);
 overScrollBy(x - oldX, y - oldY, oldX, oldY, 0, range,
 0, mOverflingDistance, false);
 onScrollChanged(mScrollX, mScrollY, oldX, oldY);
 if (canOverscroll) {
 if (y < 0 && oldY >= 0) {
 mEdgeGlowTop.onAbsorb((int) mScroller.getCurrVelocity());
 } else if (y > range && oldY <= range) {
 mEdgeGlowBottom.onAbsorb((int) mScroller.getCurrVelocity());
 }
 }
 }
 if (!awakenScrollBars()) {
 // Keep on drawing until the animation has finished.
 postInvalidateOnAnimation();
 }
 } else {
 if (mFlingStrictSpan != null) {
 mFlingStrictSpan.finish();
 mFlingStrictSpan = null;
 }
 }
 }
 /**
 * Scrolls the view to the given child.
 *
 * @param child the View to scroll to
 */
 private void scrollToChild(View child) {
 child.getDrawingRect(mTempRect);
 /* Offset from child's local coordinates to ScrollView coordinates */
 offsetDescendantRectToMyCoords(child, mTempRect);
 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect);
 if (scrollDelta != 0) {
 scrollBy(0, scrollDelta);
 }
 }
 /**
 * If rect is off screen, scroll just enough to get it (or at least the
 * first screen size chunk of it) on screen.
 *
 * @param rect The rectangle.
 * @param immediate True to scroll immediately without animation
 * @return true if scrolling was performed
 */
 private boolean scrollToChildRect(Rect rect, boolean immediate) {
 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect);
 final boolean scroll = delta != 0;
 if (scroll) {
 if (immediate) {
 scrollBy(0, delta);
 } else {
 smoothScrollBy(0, delta);
 }
 }
 return scroll;
 }
 /**
 * Compute the amount to scroll in the Y direction in order to get
 * a rectangle completely on the screen (or, if taller than the screen,
 * at least the first screen size chunk of it).
 *
 * @param rect The rect.
 * @return The scroll delta.
 */
 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) {
 if (getChildCount() == 0) return 0;
 int height = getHeight();
 int screenTop = getScrollY();
 int screenBottom = screenTop + height;
 int fadingEdge = getVerticalFadingEdgeLength();
 // leave room for top fading edge as long as rect isn't at very top
 if (rect.top > 0) {
 screenTop += fadingEdge;
 }
 // leave room for bottom fading edge as long as rect isn't at very bottom
 if (rect.bottom < getChildAt(0).getHeight()) {
 screenBottom -= fadingEdge;
 }
 int scrollYDelta = 0;
 if (rect.bottom > screenBottom && rect.top > screenTop) {
 // need to move down to get it in view: move down just enough so
 // that the entire rectangle is in view (or at least the first
 // screen size chunk).
 if (rect.height() > height) {
 // just enough to get screen size chunk on
 scrollYDelta += (rect.top - screenTop);
 } else {
 // get entire rect at bottom of screen
 scrollYDelta += (rect.bottom - screenBottom);
 }
 // make sure we aren't scrolling beyond the end of our content
 int bottom = getChildAt(0).getBottom();
 int distanceToBottom = bottom - screenBottom;
 scrollYDelta = Math.min(scrollYDelta, distanceToBottom);
 } else if (rect.top < screenTop && rect.bottom < screenBottom) {
 // need to move up to get it in view: move up just enough so that
 // entire rectangle is in view (or at least the first screen
 // size chunk of it).
 if (rect.height() > height) {
 // screen size chunk
 scrollYDelta -= (screenBottom - rect.bottom);
 } else {
 // entire rect at top
 scrollYDelta -= (screenTop - rect.top);
 }
 // make sure we aren't scrolling any further than the top our content
 scrollYDelta = Math.max(scrollYDelta, -getScrollY());
 }
 return scrollYDelta;
 }
 @Override
 public void requestChildFocus(View child, View focused) {
 if (!mIsLayoutDirty) {
 scrollToChild(focused);
 } else {
 // The child may not be laid out yet, we can't compute the scroll yet
 mChildToScrollTo = focused;
 }
 super.requestChildFocus(child, focused);
 }
 /**
 * When looking for focus in children of a scroll view, need to be a little
 * more careful not to give focus to something that is scrolled off screen.
 *
 * This is more expensive than the default {@link android.view.ViewGroup}
 * implementation, otherwise this behavior might have been made the default.
 */
 @Override
 protected boolean onRequestFocusInDescendants(int direction,
 Rect previouslyFocusedRect) {
 // convert from forward / backward notation to up / down / left / right
 // (ugh).
 if (direction == View.FOCUS_FORWARD) {
 direction = View.FOCUS_DOWN;
 } else if (direction == View.FOCUS_BACKWARD) {
 direction = View.FOCUS_UP;
 }
 final View nextFocus = previouslyFocusedRect == null ?
 FocusFinder.getInstance().findNextFocus(this, null, direction) :
 FocusFinder.getInstance().findNextFocusFromRect(this,
 previouslyFocusedRect, direction);
 if (nextFocus == null) {
 return false;
 }
 if (isOffScreen(nextFocus)) {
 return false;
 }
 return nextFocus.requestFocus(direction, previouslyFocusedRect);
 }
 @Override
 public boolean requestChildRectangleOnScreen(View child, Rect rectangle,
 boolean immediate) {
 // offset into coordinate space of this scroll view
 rectangle.offset(child.getLeft() - child.getScrollX(),
 child.getTop() - child.getScrollY());
 return scrollToChildRect(rectangle, immediate);
 }
 @Override
 public void requestLayout() {
 mIsLayoutDirty = true;
 super.requestLayout();
 }
 @Override
 protected void onDetachedFromWindow() {
 super.onDetachedFromWindow();
 if (mScrollStrictSpan != null) {
 mScrollStrictSpan.finish();
 mScrollStrictSpan = null;
 }
 if (mFlingStrictSpan != null) {
 mFlingStrictSpan.finish();
 mFlingStrictSpan = null;
 }
 }
 @Override
 protected void onLayout(boolean changed, int l, int t, int r, int b) {
 super.onLayout(changed, l, t, r, b);
 mIsLayoutDirty = false;
 // Give a child focus if it needs it
 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) {
 scrollToChild(mChildToScrollTo);
 }
 mChildToScrollTo = null;
 // Calling this with the present values causes it to re-claim them
 scrollTo(mScrollX, mScrollY);
 }
 @Override
 protected void onSizeChanged(int w, int h, int oldw, int oldh) {
 super.onSizeChanged(w, h, oldw, oldh);
 View currentFocused = findFocus();
 if (null == currentFocused || this == currentFocused)
 return;
 // If the currently-focused view was visible on the screen when the
 // screen was at the old height, then scroll the screen to make that
 // view visible with the new screen height.
 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) {
 currentFocused.getDrawingRect(mTempRect);
 offsetDescendantRectToMyCoords(currentFocused, mTempRect);
 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect);
 doScrollY(scrollDelta);
 }
 }
 /**
 * Return true if child is a descendant of parent, (or equal to the parent).
 */
 private static boolean isViewDescendantOf(View child, View parent) {
 if (child == parent) {
 return true;
 }
 final ViewParent theParent = child.getParent();
 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent);
 }
 /**
 * Fling the scroll view
 *
 * @param velocityY The initial velocity in the Y direction. Positive
 * numbers mean that the finger/cursor is moving down the screen,
 * which means we want to scroll towards the top.
 */
 public void fling(int velocityY) {
 if (getChildCount() > 0) {
 int height = getHeight() - mPaddingBottom - mPaddingTop;
 int bottom = getChildAt(0).getHeight();
 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0,
 Math.max(0, bottom - height), 0, height/2);
 if (mFlingStrictSpan == null) {
 mFlingStrictSpan = StrictMode.enterCriticalSpan("ScrollView-fling");
 }
 postInvalidateOnAnimation();
 }
 }
 private void endDrag() {
 mIsBeingDragged = false;
 recycleVelocityTracker();
 if (mEdgeGlowTop != null) {
 mEdgeGlowTop.onRelease();
 mEdgeGlowBottom.onRelease();
 }
 if (mScrollStrictSpan != null) {
 mScrollStrictSpan.finish();
 mScrollStrictSpan = null;
 }
 }
 /**
 * {@inheritDoc}
 *
 * This version also clamps the scrolling to the bounds of our child.
 */
 @Override
 public void scrollTo(int x, int y) {
 // we rely on the fact the View.scrollBy calls scrollTo.
 if (getChildCount() > 0) {
 View child = getChildAt(0);
 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth());
 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight());
 if (x != mScrollX || y != mScrollY) {
 super.scrollTo(x, y);
 }
 }
 }
 @Override
 public void setOverScrollMode(int mode) {
 if (mode != OVER_SCROLL_NEVER) {
 if (mEdgeGlowTop == null) {
 Context context = getContext();
 mEdgeGlowTop = new EdgeEffect(context);
 mEdgeGlowBottom = new EdgeEffect(context);
 }
 } else {
 mEdgeGlowTop = null;
 mEdgeGlowBottom = null;
 }
 super.setOverScrollMode(mode);
 }
 @Override
 public void draw(Canvas canvas) {
 super.draw(canvas);
 if (mEdgeGlowTop != null) {
 final int scrollY = mScrollY;
 if (!mEdgeGlowTop.isFinished()) {
 final int restoreCount = canvas.save();
 final int width = getWidth() - mPaddingLeft - mPaddingRight;
 canvas.translate(mPaddingLeft, Math.min(0, scrollY));
 mEdgeGlowTop.setSize(width, getHeight());
 if (mEdgeGlowTop.draw(canvas)) {
 postInvalidateOnAnimation();
 }
 canvas.restoreToCount(restoreCount);
 }
 if (!mEdgeGlowBottom.isFinished()) {
 final int restoreCount = canvas.save();
 final int width = getWidth() - mPaddingLeft - mPaddingRight;
 final int height = getHeight();
 canvas.translate(-width + mPaddingLeft,
 Math.max(getScrollRange(), scrollY) + height);
 canvas.rotate(180, width, 0);
 mEdgeGlowBottom.setSize(width, height);
 if (mEdgeGlowBottom.draw(canvas)) {
 postInvalidateOnAnimation();
 }
 canvas.restoreToCount(restoreCount);
 }
 }
 }
 private static int clamp(int n, int my, int child) {
 if (my >= child || n < 0) {
 /* my >= child is this case:
 * |--------------- me ---------------|
 * |------ child ------|
 * or
 * |--------------- me ---------------|
 * |------ child ------|
 * or
 * |--------------- me ---------------|
 * |------ child ------|
 *
 * n < 0 is this case:
 * |------ me ------|
 * |-------- child --------|
 * |-- mScrollX --|
 */
 return 0;
 }
 if ((my+n) > child) {
 /* this case:
 * |------ me ------|
 * |------ child ------|
 * |-- mScrollX --|
 */
 return child-my;
 }
 return n;
 }
}
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android / platform / frameworks / support / refs/heads/androidx-main / . / core / core / src / main / java / androidx / core / widget / NestedScrollView.java
blob: 8eebc918c45dd39c7538fa4529b184fb01dfa92e [file] [log] [blame]
/*
 * Copyright (C) 2015 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package androidx.core.widget;
import static androidx.annotation.RestrictTo.Scope.LIBRARY;
import static androidx.annotation.RestrictTo.Scope.LIBRARY_GROUP_PREFIX;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.hardware.SensorManager;
import android.os.Build;
import android.os.Bundle;
import android.os.Parcel;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.util.Log;
import android.util.TypedValue;
import android.view.FocusFinder;
import android.view.InputDevice;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.view.accessibility.AccessibilityEvent;
import android.view.animation.AnimationUtils;
import android.widget.EdgeEffect;
import android.widget.FrameLayout;
import android.widget.OverScroller;
import android.widget.ScrollView;
import androidx.annotation.DoNotInline;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.RequiresApi;
import androidx.annotation.RestrictTo;
import androidx.annotation.VisibleForTesting;
import androidx.core.R;
import androidx.core.view.AccessibilityDelegateCompat;
import androidx.core.view.DifferentialMotionFlingController;
import androidx.core.view.DifferentialMotionFlingTarget;
import androidx.core.view.MotionEventCompat;
import androidx.core.view.NestedScrollingChild3;
import androidx.core.view.NestedScrollingChildHelper;
import androidx.core.view.NestedScrollingParent3;
import androidx.core.view.NestedScrollingParentHelper;
import androidx.core.view.ScrollingView;
import androidx.core.view.ViewCompat;
import androidx.core.view.accessibility.AccessibilityNodeInfoCompat;
import androidx.core.view.accessibility.AccessibilityRecordCompat;
import java.util.List;
/**
 * NestedScrollView is just like {@link ScrollView}, but it supports acting
 * as both a nested scrolling parent and child on both new and old versions of Android.
 * Nested scrolling is enabled by default.
 */
public class NestedScrollView extends FrameLayout implements NestedScrollingParent3,
 NestedScrollingChild3, ScrollingView {
 static final int ANIMATED_SCROLL_GAP = 250;
 static final float MAX_SCROLL_FACTOR = 0.5f;
 private static final String TAG = "NestedScrollView";
 private static final int DEFAULT_SMOOTH_SCROLL_DURATION = 250;
 /**
 * The following are copied from OverScroller to determine how far a fling will go.
 */
 private static final float SCROLL_FRICTION = 0.015f;
 private static final float INFLEXION = 0.35f; // Tension lines cross at (INFLEXION, 1)
 private static final float DECELERATION_RATE = (float) (Math.log(0.78) / Math.log(0.9));
 private final float mPhysicalCoeff;
 /**
 * When flinging the stretch towards scrolling content, it should destretch quicker than the
 * fling would normally do. The visual effect of flinging the stretch looks strange as little
 * appears to happen at first and then when the stretch disappears, the content starts
 * scrolling quickly.
 */
 private static final float FLING_DESTRETCH_FACTOR = 4f;
 /**
 * Interface definition for a callback to be invoked when the scroll
 * X or Y positions of a view change.
 *
 * This version of the interface works on all versions of Android, back to API v4.
 *
 * @see #setOnScrollChangeListener(OnScrollChangeListener)
 */
 public interface OnScrollChangeListener {
 /**
 * Called when the scroll position of a view changes.
 * @param v The view whose scroll position has changed.
 * @param scrollX Current horizontal scroll origin.
 * @param scrollY Current vertical scroll origin.
 * @param oldScrollX Previous horizontal scroll origin.
 * @param oldScrollY Previous vertical scroll origin.
 */
 void onScrollChange(@NonNull NestedScrollView v, int scrollX, int scrollY,
 int oldScrollX, int oldScrollY);
 }
 private long mLastScroll;
 private final Rect mTempRect = new Rect();
 private OverScroller mScroller;
 @RestrictTo(LIBRARY)
 @VisibleForTesting
 @NonNull
 public EdgeEffect mEdgeGlowTop;
 @RestrictTo(LIBRARY)
 @VisibleForTesting
 @NonNull
 public EdgeEffect mEdgeGlowBottom;
 /**
 * Position of the last motion event; only used with touch related events (usually to assist
 * in movement changes in a drag gesture).
 */
 private int mLastMotionY;
 /**
 * True when the layout has changed but the traversal has not come through yet.
 * Ideally the view hierarchy would keep track of this for us.
 */
 private boolean mIsLayoutDirty = true;
 private boolean mIsLaidOut = false;
 /**
 * The child to give focus to in the event that a child has requested focus while the
 * layout is dirty. This prevents the scroll from being wrong if the child has not been
 * laid out before requesting focus.
 */
 private View mChildToScrollTo = null;
 /**
 * True if the user is currently dragging this ScrollView around. This is
 * not the same as 'is being flinged', which can be checked by
 * mScroller.isFinished() (flinging begins when the user lifts their finger).
 */
 private boolean mIsBeingDragged = false;
 /**
 * Determines speed during touch scrolling
 */
 private VelocityTracker mVelocityTracker;
 /**
 * When set to true, the scroll view measure its child to make it fill the currently
 * visible area.
 */
 private boolean mFillViewport;
 /**
 * Whether arrow scrolling is animated.
 */
 private boolean mSmoothScrollingEnabled = true;
 private int mTouchSlop;
 private int mMinimumVelocity;
 private int mMaximumVelocity;
 /**
 * ID of the active pointer. This is used to retain consistency during
 * drags/flings if multiple pointers are used.
 */
 private int mActivePointerId = INVALID_POINTER;
 /**
 * Used during scrolling to retrieve the new offset within the window. Saves memory by saving
 * x, y changes to this array (0 position = x, 1 position = y) vs. reallocating an x and y
 * every time.
 */
 private final int[] mScrollOffset = new int[2];
 /*
 * Used during scrolling to retrieve the new consumed offset within the window.
 * Uses same memory saving strategy as mScrollOffset.
 */
 private final int[] mScrollConsumed = new int[2];
 // Used to track the position of the touch only events relative to the container.
 private int mNestedYOffset;
 private int mLastScrollerY;
 /**
 * Sentinel value for no current active pointer.
 * Used by {@link #mActivePointerId}.
 */
 private static final int INVALID_POINTER = -1;
 private SavedState mSavedState;
 private static final AccessibilityDelegate ACCESSIBILITY_DELEGATE = new AccessibilityDelegate();
 private static final int[] SCROLLVIEW_STYLEABLE = new int[] {
 android.R.attr.fillViewport
 };
 private final NestedScrollingParentHelper mParentHelper;
 private final NestedScrollingChildHelper mChildHelper;
 private float mVerticalScrollFactor;
 private OnScrollChangeListener mOnScrollChangeListener;
 @VisibleForTesting
 final DifferentialMotionFlingTargetImpl mDifferentialMotionFlingTarget =
 new DifferentialMotionFlingTargetImpl();
 @VisibleForTesting
 DifferentialMotionFlingController mDifferentialMotionFlingController =
 new DifferentialMotionFlingController(getContext(), mDifferentialMotionFlingTarget);
 public NestedScrollView(@NonNull Context context) {
 this(context, null);
 }
 public NestedScrollView(@NonNull Context context, @Nullable AttributeSet attrs) {
 this(context, attrs, R.attr.nestedScrollViewStyle);
 }
 public NestedScrollView(@NonNull Context context, @Nullable AttributeSet attrs,
 int defStyleAttr) {
 super(context, attrs, defStyleAttr);
 mEdgeGlowTop = EdgeEffectCompat.create(context, attrs);
 mEdgeGlowBottom = EdgeEffectCompat.create(context, attrs);
 final float ppi = context.getResources().getDisplayMetrics().density * 160.0f;
 mPhysicalCoeff = SensorManager.GRAVITY_EARTH // g (m/s^2)
 * 39.37f // inch/meter
 * ppi
 * 0.84f; // look and feel tuning
 initScrollView();
 final TypedArray a = context.obtainStyledAttributes(
 attrs, SCROLLVIEW_STYLEABLE, defStyleAttr, 0);
 setFillViewport(a.getBoolean(0, false));
 a.recycle();
 mParentHelper = new NestedScrollingParentHelper(this);
 mChildHelper = new NestedScrollingChildHelper(this);
 // ...because why else would you be using this widget?
 setNestedScrollingEnabled(true);
 ViewCompat.setAccessibilityDelegate(this, ACCESSIBILITY_DELEGATE);
 }
 // NestedScrollingChild3
 @Override
 public void dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed,
 int dyUnconsumed, @Nullable int[] offsetInWindow, int type, @NonNull int[] consumed) {
 mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed,
 offsetInWindow, type, consumed);
 }
 // NestedScrollingChild2
 @Override
 public boolean startNestedScroll(int axes, int type) {
 return mChildHelper.startNestedScroll(axes, type);
 }
 @Override
 public void stopNestedScroll(int type) {
 mChildHelper.stopNestedScroll(type);
 }
 @Override
 public boolean hasNestedScrollingParent(int type) {
 return mChildHelper.hasNestedScrollingParent(type);
 }
 @Override
 public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed,
 int dyUnconsumed, @Nullable int[] offsetInWindow, int type) {
 return mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed,
 offsetInWindow, type);
 }
 @Override
 public boolean dispatchNestedPreScroll(
 int dx,
 int dy,
 @Nullable int[] consumed,
 @Nullable int[] offsetInWindow,
 int type
 ) {
 return mChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type);
 }
 // NestedScrollingChild
 @Override
 public void setNestedScrollingEnabled(boolean enabled) {
 mChildHelper.setNestedScrollingEnabled(enabled);
 }
 @Override
 public boolean isNestedScrollingEnabled() {
 return mChildHelper.isNestedScrollingEnabled();
 }
 @Override
 public boolean startNestedScroll(int axes) {
 return startNestedScroll(axes, ViewCompat.TYPE_TOUCH);
 }
 @Override
 public void stopNestedScroll() {
 stopNestedScroll(ViewCompat.TYPE_TOUCH);
 }
 @Override
 public boolean hasNestedScrollingParent() {
 return hasNestedScrollingParent(ViewCompat.TYPE_TOUCH);
 }
 @Override
 public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed,
 int dyUnconsumed, @Nullable int[] offsetInWindow) {
 return mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed,
 offsetInWindow);
 }
 @Override
 public boolean dispatchNestedPreScroll(int dx, int dy, @Nullable int[] consumed,
 @Nullable int[] offsetInWindow) {
 return dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, ViewCompat.TYPE_TOUCH);
 }
 @Override
 public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
 return mChildHelper.dispatchNestedFling(velocityX, velocityY, consumed);
 }
 @Override
 public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
 return mChildHelper.dispatchNestedPreFling(velocityX, velocityY);
 }
 // NestedScrollingParent3
 @Override
 public void onNestedScroll(@NonNull View target, int dxConsumed, int dyConsumed,
 int dxUnconsumed, int dyUnconsumed, int type, @NonNull int[] consumed) {
 onNestedScrollInternal(dyUnconsumed, type, consumed);
 }
 private void onNestedScrollInternal(int dyUnconsumed, int type, @Nullable int[] consumed) {
 final int oldScrollY = getScrollY();
 scrollBy(0, dyUnconsumed);
 final int myConsumed = getScrollY() - oldScrollY;
 if (consumed != null) {
 consumed[1] += myConsumed;
 }
 final int myUnconsumed = dyUnconsumed - myConsumed;
 mChildHelper.dispatchNestedScroll(0, myConsumed, 0, myUnconsumed, null, type, consumed);
 }
 // NestedScrollingParent2
 @Override
 public boolean onStartNestedScroll(@NonNull View child, @NonNull View target, int axes,
 int type) {
 return (axes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0;
 }
 @Override
 public void onNestedScrollAccepted(@NonNull View child, @NonNull View target, int axes,
 int type) {
 mParentHelper.onNestedScrollAccepted(child, target, axes, type);
 startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL, type);
 }
 @Override
 public void onStopNestedScroll(@NonNull View target, int type) {
 mParentHelper.onStopNestedScroll(target, type);
 stopNestedScroll(type);
 }
 @Override
 public void onNestedScroll(@NonNull View target, int dxConsumed, int dyConsumed,
 int dxUnconsumed, int dyUnconsumed, int type) {
 onNestedScrollInternal(dyUnconsumed, type, null);
 }
 @Override
 public void onNestedPreScroll(@NonNull View target, int dx, int dy, @NonNull int[] consumed,
 int type) {
 dispatchNestedPreScroll(dx, dy, consumed, null, type);
 }
 // NestedScrollingParent
 @Override
 public boolean onStartNestedScroll(
 @NonNull View child, @NonNull View target, int axes) {
 return onStartNestedScroll(child, target, axes, ViewCompat.TYPE_TOUCH);
 }
 @Override
 public void onNestedScrollAccepted(
 @NonNull View child, @NonNull View target, int axes) {
 onNestedScrollAccepted(child, target, axes, ViewCompat.TYPE_TOUCH);
 }
 @Override
 public void onStopNestedScroll(@NonNull View target) {
 onStopNestedScroll(target, ViewCompat.TYPE_TOUCH);
 }
 @Override
 public void onNestedScroll(@NonNull View target, int dxConsumed, int dyConsumed,
 int dxUnconsumed, int dyUnconsumed) {
 onNestedScrollInternal(dyUnconsumed, ViewCompat.TYPE_TOUCH, null);
 }
 @Override
 public void onNestedPreScroll(@NonNull View target, int dx, int dy, @NonNull int[] consumed) {
 onNestedPreScroll(target, dx, dy, consumed, ViewCompat.TYPE_TOUCH);
 }
 @Override
 public boolean onNestedFling(
 @NonNull View target, float velocityX, float velocityY, boolean consumed) {
 if (!consumed) {
 dispatchNestedFling(0, velocityY, true);
 fling((int) velocityY);
 return true;
 }
 return false;
 }
 @Override
 public boolean onNestedPreFling(@NonNull View target, float velocityX, float velocityY) {
 return dispatchNestedPreFling(velocityX, velocityY);
 }
 @Override
 public int getNestedScrollAxes() {
 return mParentHelper.getNestedScrollAxes();
 }
 // ScrollView import
 @Override
 public boolean shouldDelayChildPressedState() {
 return true;
 }
 @Override
 protected float getTopFadingEdgeStrength() {
 if (getChildCount() == 0) {
 return 0.0f;
 }
 final int length = getVerticalFadingEdgeLength();
 final int scrollY = getScrollY();
 if (scrollY < length) {
 return scrollY / (float) length;
 }
 return 1.0f;
 }
 @Override
 protected float getBottomFadingEdgeStrength() {
 if (getChildCount() == 0) {
 return 0.0f;
 }
 View child = getChildAt(0);
 final LayoutParams lp = (LayoutParams) child.getLayoutParams();
 final int length = getVerticalFadingEdgeLength();
 final int bottomEdge = getHeight() - getPaddingBottom();
 final int span = child.getBottom() + lp.bottomMargin - getScrollY() - bottomEdge;
 if (span < length) {
 return span / (float) length;
 }
 return 1.0f;
 }
 /**
 * @return The maximum amount this scroll view will scroll in response to
 * an arrow event.
 */
 public int getMaxScrollAmount() {
 return (int) (MAX_SCROLL_FACTOR * getHeight());
 }
 private void initScrollView() {
 mScroller = new OverScroller(getContext());
 setFocusable(true);
 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS);
 setWillNotDraw(false);
 final ViewConfiguration configuration = ViewConfiguration.get(getContext());
 mTouchSlop = configuration.getScaledTouchSlop();
 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();
 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
 }
 @Override
 public void addView(@NonNull View child) {
 if (getChildCount() > 0) {
 throw new IllegalStateException("ScrollView can host only one direct child");
 }
 super.addView(child);
 }
 @Override
 public void addView(View child, int index) {
 if (getChildCount() > 0) {
 throw new IllegalStateException("ScrollView can host only one direct child");
 }
 super.addView(child, index);
 }
 @Override
 public void addView(View child, ViewGroup.LayoutParams params) {
 if (getChildCount() > 0) {
 throw new IllegalStateException("ScrollView can host only one direct child");
 }
 super.addView(child, params);
 }
 @Override
 public void addView(View child, int index, ViewGroup.LayoutParams params) {
 if (getChildCount() > 0) {
 throw new IllegalStateException("ScrollView can host only one direct child");
 }
 super.addView(child, index, params);
 }
 /**
 * Register a callback to be invoked when the scroll X or Y positions of
 * this view change.
 * This version of the method works on all versions of Android, back to API v4.
 *
 * @param l The listener to notify when the scroll X or Y position changes.
 * @see View#getScrollX()
 * @see View#getScrollY()
 */
 public void setOnScrollChangeListener(@Nullable OnScrollChangeListener l) {
 mOnScrollChangeListener = l;
 }
 /**
 * @return Returns true this ScrollView can be scrolled
 */
 private boolean canScroll() {
 if (getChildCount() > 0) {
 View child = getChildAt(0);
 final LayoutParams lp = (LayoutParams) child.getLayoutParams();
 int childSize = child.getHeight() + lp.topMargin + lp.bottomMargin;
 int parentSpace = getHeight() - getPaddingTop() - getPaddingBottom();
 return childSize > parentSpace;
 }
 return false;
 }
 /**
 * Indicates whether this ScrollView's content is stretched to fill the viewport.
 *
 * @return True if the content fills the viewport, false otherwise.
 *
 * @attr name android:fillViewport
 */
 public boolean isFillViewport() {
 return mFillViewport;
 }
 /**
 * Set whether this ScrollView should stretch its content height to fill the viewport or not.
 *
 * @param fillViewport True to stretch the content's height to the viewport's
 * boundaries, false otherwise.
 *
 * @attr name android:fillViewport
 */
 public void setFillViewport(boolean fillViewport) {
 if (fillViewport != mFillViewport) {
 mFillViewport = fillViewport;
 requestLayout();
 }
 }
 /**
 * @return Whether arrow scrolling will animate its transition.
 */
 public boolean isSmoothScrollingEnabled() {
 return mSmoothScrollingEnabled;
 }
 /**
 * Set whether arrow scrolling will animate its transition.
 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition
 */
 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) {
 mSmoothScrollingEnabled = smoothScrollingEnabled;
 }
 @Override
 protected void onScrollChanged(int l, int t, int oldl, int oldt) {
 super.onScrollChanged(l, t, oldl, oldt);
 if (mOnScrollChangeListener != null) {
 mOnScrollChangeListener.onScrollChange(this, l, t, oldl, oldt);
 }
 }
 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
 super.onMeasure(widthMeasureSpec, heightMeasureSpec);
 if (!mFillViewport) {
 return;
 }
 final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
 if (heightMode == MeasureSpec.UNSPECIFIED) {
 return;
 }
 if (getChildCount() > 0) {
 View child = getChildAt(0);
 final LayoutParams lp = (LayoutParams) child.getLayoutParams();
 int childSize = child.getMeasuredHeight();
 int parentSpace = getMeasuredHeight()
 - getPaddingTop()
 - getPaddingBottom()
 - lp.topMargin
 - lp.bottomMargin;
 if (childSize < parentSpace) {
 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec,
 getPaddingLeft() + getPaddingRight() + lp.leftMargin + lp.rightMargin,
 lp.width);
 int childHeightMeasureSpec =
 MeasureSpec.makeMeasureSpec(parentSpace, MeasureSpec.EXACTLY);
 child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
 }
 }
 }
 @Override
 public boolean dispatchKeyEvent(KeyEvent event) {
 // Let the focused view and/or our descendants get the key first
 return super.dispatchKeyEvent(event) || executeKeyEvent(event);
 }
 /**
 * You can call this function yourself to have the scroll view perform
 * scrolling from a key event, just as if the event had been dispatched to
 * it by the view hierarchy.
 *
 * @param event The key event to execute.
 * @return Return true if the event was handled, else false.
 */
 public boolean executeKeyEvent(@NonNull KeyEvent event) {
 mTempRect.setEmpty();
 if (!canScroll()) {
 if (isFocused() && event.getKeyCode() != KeyEvent.KEYCODE_BACK) {
 View currentFocused = findFocus();
 if (currentFocused == this) currentFocused = null;
 View nextFocused = FocusFinder.getInstance().findNextFocus(this,
 currentFocused, View.FOCUS_DOWN);
 return nextFocused != null
 && nextFocused != this
 && nextFocused.requestFocus(View.FOCUS_DOWN);
 }
 return false;
 }
 boolean handled = false;
 if (event.getAction() == KeyEvent.ACTION_DOWN) {
 switch (event.getKeyCode()) {
 case KeyEvent.KEYCODE_DPAD_UP:
 if (event.isAltPressed()) {
 handled = fullScroll(View.FOCUS_UP);
 } else {
 handled = arrowScroll(View.FOCUS_UP);
 }
 break;
 case KeyEvent.KEYCODE_DPAD_DOWN:
 if (event.isAltPressed()) {
 handled = fullScroll(View.FOCUS_DOWN);
 } else {
 handled = arrowScroll(View.FOCUS_DOWN);
 }
 break;
 case KeyEvent.KEYCODE_PAGE_UP:
 handled = fullScroll(View.FOCUS_UP);
 break;
 case KeyEvent.KEYCODE_PAGE_DOWN:
 handled = fullScroll(View.FOCUS_DOWN);
 break;
 case KeyEvent.KEYCODE_SPACE:
 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN);
 break;
 case KeyEvent.KEYCODE_MOVE_HOME:
 pageScroll(View.FOCUS_UP);
 break;
 case KeyEvent.KEYCODE_MOVE_END:
 pageScroll(View.FOCUS_DOWN);
 break;
 }
 }
 return handled;
 }
 private boolean inChild(int x, int y) {
 if (getChildCount() > 0) {
 final int scrollY = getScrollY();
 final View child = getChildAt(0);
 return !(y < child.getTop() - scrollY
 || y >= child.getBottom() - scrollY
 || x < child.getLeft()
 || x >= child.getRight());
 }
 return false;
 }
 private void initOrResetVelocityTracker() {
 if (mVelocityTracker == null) {
 mVelocityTracker = VelocityTracker.obtain();
 } else {
 mVelocityTracker.clear();
 }
 }
 private void initVelocityTrackerIfNotExists() {
 if (mVelocityTracker == null) {
 mVelocityTracker = VelocityTracker.obtain();
 }
 }
 private void recycleVelocityTracker() {
 if (mVelocityTracker != null) {
 mVelocityTracker.recycle();
 mVelocityTracker = null;
 }
 }
 @Override
 public void requestDisallowInterceptTouchEvent(boolean disallowIntercept) {
 if (disallowIntercept) {
 recycleVelocityTracker();
 }
 super.requestDisallowInterceptTouchEvent(disallowIntercept);
 }
 @Override
 public boolean onInterceptTouchEvent(@NonNull MotionEvent ev) {
 /*
 * This method JUST determines whether we want to intercept the motion.
 * If we return true, onMotionEvent will be called and we do the actual
 * scrolling there.
 */
 /*
 * Shortcut the most recurring case: the user is in the dragging
 * state and they are moving their finger. We want to intercept this
 * motion.
 */
 final int action = ev.getAction();
 if ((action == MotionEvent.ACTION_MOVE) && mIsBeingDragged) {
 return true;
 }
 switch (action & MotionEvent.ACTION_MASK) {
 case MotionEvent.ACTION_MOVE: {
 /*
 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check
 * whether the user has moved far enough from their original down touch.
 */
 /*
 * Locally do absolute value. mLastMotionY is set to the y value
 * of the down event.
 */
 final int activePointerId = mActivePointerId;
 if (activePointerId == INVALID_POINTER) {
 // If we don't have a valid id, the touch down wasn't on content.
 break;
 }
 final int pointerIndex = ev.findPointerIndex(activePointerId);
 if (pointerIndex == -1) {
 Log.e(TAG, "Invalid pointerId=" + activePointerId
 + " in onInterceptTouchEvent");
 break;
 }
 final int y = (int) ev.getY(pointerIndex);
 final int yDiff = Math.abs(y - mLastMotionY);
 if (yDiff > mTouchSlop
 && (getNestedScrollAxes() & ViewCompat.SCROLL_AXIS_VERTICAL) == 0) {
 mIsBeingDragged = true;
 mLastMotionY = y;
 initVelocityTrackerIfNotExists();
 mVelocityTracker.addMovement(ev);
 mNestedYOffset = 0;
 final ViewParent parent = getParent();
 if (parent != null) {
 parent.requestDisallowInterceptTouchEvent(true);
 }
 }
 break;
 }
 case MotionEvent.ACTION_DOWN: {
 final int y = (int) ev.getY();
 if (!inChild((int) ev.getX(), y)) {
 mIsBeingDragged = stopGlowAnimations(ev) || !mScroller.isFinished();
 recycleVelocityTracker();
 break;
 }
 /*
 * Remember location of down touch.
 * ACTION_DOWN always refers to pointer index 0.
 */
 mLastMotionY = y;
 mActivePointerId = ev.getPointerId(0);
 initOrResetVelocityTracker();
 mVelocityTracker.addMovement(ev);
 /*
 * If being flinged and user touches the screen, initiate drag;
 * otherwise don't. mScroller.isFinished should be false when
 * being flinged. We also want to catch the edge glow and start dragging
 * if one is being animated. We need to call computeScrollOffset() first so that
 * isFinished() is correct.
 */
 mScroller.computeScrollOffset();
 mIsBeingDragged = stopGlowAnimations(ev) || !mScroller.isFinished();
 startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL, ViewCompat.TYPE_TOUCH);
 break;
 }
 case MotionEvent.ACTION_CANCEL:
 case MotionEvent.ACTION_UP:
 /* Release the drag */
 mIsBeingDragged = false;
 mActivePointerId = INVALID_POINTER;
 recycleVelocityTracker();
 if (mScroller.springBack(getScrollX(), getScrollY(), 0, 0, 0, getScrollRange())) {
 postInvalidateOnAnimation();
 }
 stopNestedScroll(ViewCompat.TYPE_TOUCH);
 break;
 case MotionEvent.ACTION_POINTER_UP:
 onSecondaryPointerUp(ev);
 break;
 }
 /*
 * The only time we want to intercept motion events is if we are in the
 * drag mode.
 */
 return mIsBeingDragged;
 }
 @Override
 public boolean onTouchEvent(@NonNull MotionEvent motionEvent) {
 initVelocityTrackerIfNotExists();
 final int actionMasked = motionEvent.getActionMasked();
 if (actionMasked == MotionEvent.ACTION_DOWN) {
 mNestedYOffset = 0;
 }
 MotionEvent velocityTrackerMotionEvent = MotionEvent.obtain(motionEvent);
 velocityTrackerMotionEvent.offsetLocation(0, mNestedYOffset);
 switch (actionMasked) {
 case MotionEvent.ACTION_DOWN: {
 if (getChildCount() == 0) {
 return false;
 }
 // If additional fingers touch the screen while a drag is in progress, this block
 // of code will make sure the drag isn't interrupted.
 if (mIsBeingDragged) {
 final ViewParent parent = getParent();
 if (parent != null) {
 parent.requestDisallowInterceptTouchEvent(true);
 }
 }
 /*
 * If being flinged and user touches, stop the fling. isFinished
 * will be false if being flinged.
 */
 if (!mScroller.isFinished()) {
 abortAnimatedScroll();
 }
 initializeTouchDrag(
 (int) motionEvent.getY(),
 motionEvent.getPointerId(0)
 );
 break;
 }
 case MotionEvent.ACTION_MOVE: {
 final int activePointerIndex = motionEvent.findPointerIndex(mActivePointerId);
 if (activePointerIndex == -1) {
 Log.e(TAG, "Invalid pointerId=" + mActivePointerId + " in onTouchEvent");
 break;
 }
 final int y = (int) motionEvent.getY(activePointerIndex);
 int deltaY = mLastMotionY - y;
 deltaY -= releaseVerticalGlow(deltaY, motionEvent.getX(activePointerIndex));
 // Changes to dragged state if delta is greater than the slop (and not in
 // the dragged state).
 if (!mIsBeingDragged && Math.abs(deltaY) > mTouchSlop) {
 final ViewParent parent = getParent();
 if (parent != null) {
 parent.requestDisallowInterceptTouchEvent(true);
 }
 mIsBeingDragged = true;
 if (deltaY > 0) {
 deltaY -= mTouchSlop;
 } else {
 deltaY += mTouchSlop;
 }
 }
 if (mIsBeingDragged) {
 final int x = (int) motionEvent.getX(activePointerIndex);
 int scrollOffset = scrollBy(deltaY, x, ViewCompat.TYPE_TOUCH, false);
 // Updates the global positions (used by later move events to properly scroll).
 mLastMotionY = y - scrollOffset;
 mNestedYOffset += scrollOffset;
 }
 break;
 }
 case MotionEvent.ACTION_UP: {
 final VelocityTracker velocityTracker = mVelocityTracker;
 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
 int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId);
 if ((Math.abs(initialVelocity) >= mMinimumVelocity)) {
 if (!edgeEffectFling(initialVelocity)
 && !dispatchNestedPreFling(0, -initialVelocity)) {
 dispatchNestedFling(0, -initialVelocity, true);
 fling(-initialVelocity);
 }
 } else if (mScroller.springBack(getScrollX(), getScrollY(), 0, 0, 0,
 getScrollRange())) {
 postInvalidateOnAnimation();
 }
 endTouchDrag();
 break;
 }
 case MotionEvent.ACTION_CANCEL: {
 if (mIsBeingDragged && getChildCount() > 0) {
 if (mScroller.springBack(getScrollX(), getScrollY(), 0, 0, 0,
 getScrollRange())) {
 postInvalidateOnAnimation();
 }
 }
 endTouchDrag();
 break;
 }
 case MotionEvent.ACTION_POINTER_DOWN: {
 final int index = motionEvent.getActionIndex();
 mLastMotionY = (int) motionEvent.getY(index);
 mActivePointerId = motionEvent.getPointerId(index);
 break;
 }
 case MotionEvent.ACTION_POINTER_UP: {
 onSecondaryPointerUp(motionEvent);
 mLastMotionY =
 (int) motionEvent.getY(motionEvent.findPointerIndex(mActivePointerId));
 break;
 }
 }
 if (mVelocityTracker != null) {
 mVelocityTracker.addMovement(velocityTrackerMotionEvent);
 }
 // Returns object back to be re-used by others.
 velocityTrackerMotionEvent.recycle();
 return true;
 }
 private void initializeTouchDrag(int lastMotionY, int activePointerId) {
 mLastMotionY = lastMotionY;
 mActivePointerId = activePointerId;
 startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL, ViewCompat.TYPE_TOUCH);
 }
 // Ends drag in a nested scroll.
 private void endTouchDrag() {
 mActivePointerId = INVALID_POINTER;
 mIsBeingDragged = false;
 recycleVelocityTracker();
 stopNestedScroll(ViewCompat.TYPE_TOUCH);
 mEdgeGlowTop.onRelease();
 mEdgeGlowBottom.onRelease();
 }
 /*
 * Handles scroll events for both touch and non-touch events (mouse scroll wheel,
 * rotary button, keyboard, etc.).
 *
 * Note: This function returns the total scroll offset for this scroll event which is required
 * for calculating the total scroll between multiple move events (touch). This returned value
 * is NOT needed for non-touch events since a scroll is a one time event (vs. touch where a
 * drag may be triggered multiple times with the movement of the finger).
 */
 // TODO: You should rename this to nestedScrollBy() so it is different from View.scrollBy
 private int scrollBy(
 int verticalScrollDistance,
 int x,
 int touchType,
 boolean isSourceMouseOrKeyboard
 ) {
 int totalScrollOffset = 0;
 /*
 * Starts nested scrolling for non-touch events (mouse scroll wheel, rotary button, etc.).
 * This is in contrast to a touch event which would trigger the start of nested scrolling
 * with a touch down event outside of this method, since for a single gesture scrollBy()
 * might be called several times for a move event for a single drag gesture.
 */
 if (touchType == ViewCompat.TYPE_NON_TOUCH) {
 startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL, touchType);
 }
 // Dispatches scrolling delta amount available to parent (to consume what it needs).
 // Note: The amounts the parent consumes are saved in arrays named mScrollConsumed and
 // mScrollConsumed to save space.
 if (dispatchNestedPreScroll(
 0,
 verticalScrollDistance,
 mScrollConsumed,
 mScrollOffset,
 touchType)
 ) {
 // Deducts the scroll amount (y) consumed by the parent (x in position 0,
 // y in position 1). Nested scroll only works with Y position (so we don't use x).
 verticalScrollDistance -= mScrollConsumed[1];
 totalScrollOffset += mScrollOffset[1];
 }
 // Retrieves the scroll y position (top position of this view) and scroll Y range (how far
 // the scroll can go).
 final int initialScrollY = getScrollY();
 final int scrollRangeY = getScrollRange();
 // Overscroll is for adding animations at the top/bottom of a view when the user scrolls
 // beyond the beginning/end of the view. Overscroll is not used with a mouse.
 boolean canOverscroll = canOverScroll() && !isSourceMouseOrKeyboard;
 // Scrolls content in the current View, but clamps it if it goes too far.
 boolean hitScrollBarrier =
 overScrollByCompat(
 0,
 verticalScrollDistance,
 0,
 initialScrollY,
 0,
 scrollRangeY,
 0,
 0,
 true
 ) && !hasNestedScrollingParent(touchType);
 // The position may have been adjusted in the previous call, so we must revise our values.
 final int scrollYDelta = getScrollY() - initialScrollY;
 final int unconsumedY = verticalScrollDistance - scrollYDelta;
 // Reset the Y consumed scroll to zero
 mScrollConsumed[1] = 0;
 // Dispatch the unconsumed delta Y to the children to consume.
 dispatchNestedScroll(
 0,
 scrollYDelta,
 0,
 unconsumedY,
 mScrollOffset,
 touchType,
 mScrollConsumed
 );
 totalScrollOffset += mScrollOffset[1];
 // Handle overscroll of the children.
 verticalScrollDistance -= mScrollConsumed[1];
 int newScrollY = initialScrollY + verticalScrollDistance;
 if (newScrollY < 0) {
 if (canOverscroll) {
 EdgeEffectCompat.onPullDistance(
 mEdgeGlowTop,
 (float) -verticalScrollDistance / getHeight(),
 (float) x / getWidth()
 );
 if (!mEdgeGlowBottom.isFinished()) {
 mEdgeGlowBottom.onRelease();
 }
 }
 } else if (newScrollY > scrollRangeY) {
 if (canOverscroll) {
 EdgeEffectCompat.onPullDistance(
 mEdgeGlowBottom,
 (float) verticalScrollDistance / getHeight(),
 1.f - ((float) x / getWidth())
 );
 if (!mEdgeGlowTop.isFinished()) {
 mEdgeGlowTop.onRelease();
 }
 }
 }
 if (!mEdgeGlowTop.isFinished() || !mEdgeGlowBottom.isFinished()) {
 postInvalidateOnAnimation();
 hitScrollBarrier = false;
 }
 if (hitScrollBarrier && (touchType == ViewCompat.TYPE_TOUCH)) {
 // Break our velocity if we hit a scroll barrier.
 if (mVelocityTracker != null) {
 mVelocityTracker.clear();
 }
 }
 /*
 * Ends nested scrolling for non-touch events (mouse scroll wheel, rotary button, etc.).
 * As noted above, this is in contrast to a touch event.
 */
 if (touchType == ViewCompat.TYPE_NON_TOUCH) {
 stopNestedScroll(touchType);
 // Required for scrolling with Rotary Device stretch top/bottom to work properly
 mEdgeGlowTop.onRelease();
 mEdgeGlowBottom.onRelease();
 }
 return totalScrollOffset;
 }
 /**
 * Returns true if edgeEffect should call onAbsorb() with veclocity or false if it should
 * animate with a fling. It will animate with a fling if the velocity will remove the
 * EdgeEffect through its normal operation.
 *
 * @param edgeEffect The EdgeEffect that might absorb the velocity.
 * @param velocity The velocity of the fling motion
 * @return true if the velocity should be absorbed or false if it should be flung.
 */
 private boolean shouldAbsorb(@NonNull EdgeEffect edgeEffect, int velocity) {
 if (velocity > 0) {
 return true;
 }
 float distance = EdgeEffectCompat.getDistance(edgeEffect) * getHeight();
 // This is flinging without the spring, so let's see if it will fling past the overscroll
 float flingDistance = getSplineFlingDistance(-velocity);
 return flingDistance < distance;
 }
 /**
 * If mTopGlow or mBottomGlow is currently active and the motion will remove some of the
 * stretch, this will consume any of unconsumedY that the glow can. If the motion would
 * increase the stretch, or the EdgeEffect isn't a stretch, then nothing will be consumed.
 *
 * @param unconsumedY The vertical delta that might be consumed by the vertical EdgeEffects
 * @return The remaining unconsumed delta after the edge effects have consumed.
 */
 int consumeFlingInVerticalStretch(int unconsumedY) {
 int height = getHeight();
 if (unconsumedY > 0 && EdgeEffectCompat.getDistance(mEdgeGlowTop) != 0f) {
 float deltaDistance = -unconsumedY * FLING_DESTRETCH_FACTOR / height;
 int consumed = Math.round(-height / FLING_DESTRETCH_FACTOR
 * EdgeEffectCompat.onPullDistance(mEdgeGlowTop, deltaDistance, 0.5f));
 if (consumed != unconsumedY) {
 mEdgeGlowTop.finish();
 }
 return unconsumedY - consumed;
 }
 if (unconsumedY < 0 && EdgeEffectCompat.getDistance(mEdgeGlowBottom) != 0f) {
 float deltaDistance = unconsumedY * FLING_DESTRETCH_FACTOR / height;
 int consumed = Math.round(height / FLING_DESTRETCH_FACTOR
 * EdgeEffectCompat.onPullDistance(mEdgeGlowBottom, deltaDistance, 0.5f));
 if (consumed != unconsumedY) {
 mEdgeGlowBottom.finish();
 }
 return unconsumedY - consumed;
 }
 return unconsumedY;
 }
 /**
 * Copied from OverScroller, this returns the distance that a fling with the given velocity
 * will go.
 * @param velocity The velocity of the fling
 * @return The distance that will be traveled by a fling of the given velocity.
 */
 private float getSplineFlingDistance(int velocity) {
 final double l =
 Math.log(INFLEXION * Math.abs(velocity) / (SCROLL_FRICTION * mPhysicalCoeff));
 final double decelMinusOne = DECELERATION_RATE - 1.0;
 return (float) (SCROLL_FRICTION * mPhysicalCoeff
 * Math.exp(DECELERATION_RATE / decelMinusOne * l));
 }
 private boolean edgeEffectFling(int velocityY) {
 boolean consumed = true;
 if (EdgeEffectCompat.getDistance(mEdgeGlowTop) != 0) {
 if (shouldAbsorb(mEdgeGlowTop, velocityY)) {
 mEdgeGlowTop.onAbsorb(velocityY);
 } else {
 fling(-velocityY);
 }
 } else if (EdgeEffectCompat.getDistance(mEdgeGlowBottom) != 0) {
 if (shouldAbsorb(mEdgeGlowBottom, -velocityY)) {
 mEdgeGlowBottom.onAbsorb(-velocityY);
 } else {
 fling(-velocityY);
 }
 } else {
 consumed = false;
 }
 return consumed;
 }
 /**
 * This stops any edge glow animation that is currently running by applying a
 * 0 length pull at the displacement given by the provided MotionEvent. On pre-S devices,
 * this method does nothing, allowing any animating edge effect to continue animating and
 * returning <code>false</code> always.
 *
 * @param e The motion event to use to indicate the finger position for the displacement of
 * the current pull.
 * @return <code>true</code> if any edge effect had an existing effect to be drawn ond the
 * animation was stopped or <code>false</code> if no edge effect had a value to display.
 */
 private boolean stopGlowAnimations(MotionEvent e) {
 boolean stopped = false;
 if (EdgeEffectCompat.getDistance(mEdgeGlowTop) != 0) {
 EdgeEffectCompat.onPullDistance(mEdgeGlowTop, 0, e.getX() / getWidth());
 stopped = true;
 }
 if (EdgeEffectCompat.getDistance(mEdgeGlowBottom) != 0) {
 EdgeEffectCompat.onPullDistance(mEdgeGlowBottom, 0, 1 - e.getX() / getWidth());
 stopped = true;
 }
 return stopped;
 }
 private void onSecondaryPointerUp(MotionEvent ev) {
 final int pointerIndex = ev.getActionIndex();
 final int pointerId = ev.getPointerId(pointerIndex);
 if (pointerId == mActivePointerId) {
 // This was our active pointer going up. Choose a new
 // active pointer and adjust accordingly.
 // TODO: Make this decision more intelligent.
 final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
 mLastMotionY = (int) ev.getY(newPointerIndex);
 mActivePointerId = ev.getPointerId(newPointerIndex);
 if (mVelocityTracker != null) {
 mVelocityTracker.clear();
 }
 }
 }
 @Override
 public boolean onGenericMotionEvent(@NonNull MotionEvent motionEvent) {
 if (motionEvent.getAction() == MotionEvent.ACTION_SCROLL && !mIsBeingDragged) {
 final float verticalScroll;
 final int x;
 final int flingAxis;
 if (MotionEventCompat.isFromSource(motionEvent, InputDevice.SOURCE_CLASS_POINTER)) {
 verticalScroll = motionEvent.getAxisValue(MotionEvent.AXIS_VSCROLL);
 x = (int) motionEvent.getX();
 flingAxis = MotionEvent.AXIS_VSCROLL;
 } else if (
 MotionEventCompat.isFromSource(motionEvent, InputDevice.SOURCE_ROTARY_ENCODER)
 ) {
 verticalScroll = motionEvent.getAxisValue(MotionEvent.AXIS_SCROLL);
 // Since a Wear rotary event doesn't have a true X and we want to support proper
 // overscroll animations, we put the x at the center of the screen.
 x = getWidth() / 2;
 flingAxis = MotionEvent.AXIS_SCROLL;
 } else {
 verticalScroll = 0;
 x = 0;
 flingAxis = 0;
 }
 if (verticalScroll != 0) {
 // Rotary and Mouse scrolls are inverted from a touch scroll.
 final int invertedDelta = (int) (verticalScroll * getVerticalScrollFactorCompat());
 final boolean isSourceMouse =
 MotionEventCompat.isFromSource(motionEvent, InputDevice.SOURCE_MOUSE);
 scrollBy(-invertedDelta, x, ViewCompat.TYPE_NON_TOUCH, isSourceMouse);
 if (flingAxis != 0) {
 mDifferentialMotionFlingController.onMotionEvent(motionEvent, flingAxis);
 }
 return true;
 }
 }
 return false;
 }
 /**
 * Returns true if the NestedScrollView supports over scroll.
 */
 private boolean canOverScroll() {
 final int mode = getOverScrollMode();
 return mode == OVER_SCROLL_ALWAYS
 || (mode == OVER_SCROLL_IF_CONTENT_SCROLLS && getScrollRange() > 0);
 }
 @VisibleForTesting
 float getVerticalScrollFactorCompat() {
 if (mVerticalScrollFactor == 0) {
 TypedValue outValue = new TypedValue();
 final Context context = getContext();
 if (!context.getTheme().resolveAttribute(
 android.R.attr.listPreferredItemHeight, outValue, true)) {
 throw new IllegalStateException(
 "Expected theme to define listPreferredItemHeight.");
 }
 mVerticalScrollFactor = outValue.getDimension(
 context.getResources().getDisplayMetrics());
 }
 return mVerticalScrollFactor;
 }
 @Override
 protected void onOverScrolled(int scrollX, int scrollY,
 boolean clampedX, boolean clampedY) {
 super.scrollTo(scrollX, scrollY);
 }
 @SuppressWarnings({"SameParameterValue", "unused"})
 boolean overScrollByCompat(int deltaX, int deltaY,
 int scrollX, int scrollY,
 int scrollRangeX, int scrollRangeY,
 int maxOverScrollX, int maxOverScrollY,
 boolean isTouchEvent) {
 final int overScrollMode = getOverScrollMode();
 final boolean canScrollHorizontal =
 computeHorizontalScrollRange() > computeHorizontalScrollExtent();
 final boolean canScrollVertical =
 computeVerticalScrollRange() > computeVerticalScrollExtent();
 final boolean overScrollHorizontal = overScrollMode == View.OVER_SCROLL_ALWAYS
 || (overScrollMode == View.OVER_SCROLL_IF_CONTENT_SCROLLS && canScrollHorizontal);
 final boolean overScrollVertical = overScrollMode == View.OVER_SCROLL_ALWAYS
 || (overScrollMode == View.OVER_SCROLL_IF_CONTENT_SCROLLS && canScrollVertical);
 int newScrollX = scrollX + deltaX;
 if (!overScrollHorizontal) {
 maxOverScrollX = 0;
 }
 int newScrollY = scrollY + deltaY;
 if (!overScrollVertical) {
 maxOverScrollY = 0;
 }
 // Clamp values if at the limits and record
 final int left = -maxOverScrollX;
 final int right = maxOverScrollX + scrollRangeX;
 final int top = -maxOverScrollY;
 final int bottom = maxOverScrollY + scrollRangeY;
 boolean clampedX = false;
 if (newScrollX > right) {
 newScrollX = right;
 clampedX = true;
 } else if (newScrollX < left) {
 newScrollX = left;
 clampedX = true;
 }
 boolean clampedY = false;
 if (newScrollY > bottom) {
 newScrollY = bottom;
 clampedY = true;
 } else if (newScrollY < top) {
 newScrollY = top;
 clampedY = true;
 }
 if (clampedY && !hasNestedScrollingParent(ViewCompat.TYPE_NON_TOUCH)) {
 mScroller.springBack(newScrollX, newScrollY, 0, 0, 0, getScrollRange());
 }
 onOverScrolled(newScrollX, newScrollY, clampedX, clampedY);
 return clampedX || clampedY;
 }
 int getScrollRange() {
 int scrollRange = 0;
 if (getChildCount() > 0) {
 View child = getChildAt(0);
 LayoutParams lp = (LayoutParams) child.getLayoutParams();
 int childSize = child.getHeight() + lp.topMargin + lp.bottomMargin;
 int parentSpace = getHeight() - getPaddingTop() - getPaddingBottom();
 scrollRange = Math.max(0, childSize - parentSpace);
 }
 return scrollRange;
 }
 /**
 * 
 * Finds the next focusable component that fits in the specified bounds.
 * 
 *
 * @param topFocus look for a candidate is the one at the top of the bounds
 * if topFocus is true, or at the bottom of the bounds if topFocus is
 * false
 * @param top the top offset of the bounds in which a focusable must be
 * found
 * @param bottom the bottom offset of the bounds in which a focusable must
 * be found
 * @return the next focusable component in the bounds or null if none can
 * be found
 */
 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) {
 List<View> focusables = getFocusables(View.FOCUS_FORWARD);
 View focusCandidate = null;
 /*
 * A fully contained focusable is one where its top is below the bound's
 * top, and its bottom is above the bound's bottom. A partially
 * contained focusable is one where some part of it is within the
 * bounds, but it also has some part that is not within bounds. A fully contained
 * focusable is preferred to a partially contained focusable.
 */
 boolean foundFullyContainedFocusable = false;
 int count = focusables.size();
 for (int i = 0; i < count; i++) {
 View view = focusables.get(i);
 int viewTop = view.getTop();
 int viewBottom = view.getBottom();
 if (top < viewBottom && viewTop < bottom) {
 /*
 * the focusable is in the target area, it is a candidate for
 * focusing
 */
 final boolean viewIsFullyContained = (top < viewTop) && (viewBottom < bottom);
 if (focusCandidate == null) {
 /* No candidate, take this one */
 focusCandidate = view;
 foundFullyContainedFocusable = viewIsFullyContained;
 } else {
 final boolean viewIsCloserToBoundary =
 (topFocus && viewTop < focusCandidate.getTop())
 || (!topFocus && viewBottom > focusCandidate.getBottom());
 if (foundFullyContainedFocusable) {
 if (viewIsFullyContained && viewIsCloserToBoundary) {
 /*
 * We're dealing with only fully contained views, so
 * it has to be closer to the boundary to beat our
 * candidate
 */
 focusCandidate = view;
 }
 } else {
 if (viewIsFullyContained) {
 /* Any fully contained view beats a partially contained view */
 focusCandidate = view;
 foundFullyContainedFocusable = true;
 } else if (viewIsCloserToBoundary) {
 /*
 * Partially contained view beats another partially
 * contained view if it's closer
 */
 focusCandidate = view;
 }
 }
 }
 }
 }
 return focusCandidate;
 }
 /**
 * Handles scrolling in response to a "page up/down" shortcut press. This
 * method will scroll the view by one page up or down and give the focus
 * to the topmost/bottommost component in the new visible area. If no
 * component is a good candidate for focus, this scrollview reclaims the
 * focus.
 *
 * @param direction the scroll direction: {@link View#FOCUS_UP}
 * to go one page up or
 * {@link View#FOCUS_DOWN} to go one page down
 * @return true if the key event is consumed by this method, false otherwise
 */
 public boolean pageScroll(int direction) {
 boolean down = direction == View.FOCUS_DOWN;
 int height = getHeight();
 if (down) {
 mTempRect.top = getScrollY() + height;
 int count = getChildCount();
 if (count > 0) {
 View view = getChildAt(count - 1);
 LayoutParams lp = (LayoutParams) view.getLayoutParams();
 int bottom = view.getBottom() + lp.bottomMargin + getPaddingBottom();
 if (mTempRect.top + height > bottom) {
 mTempRect.top = bottom - height;
 }
 }
 } else {
 mTempRect.top = getScrollY() - height;
 if (mTempRect.top < 0) {
 mTempRect.top = 0;
 }
 }
 mTempRect.bottom = mTempRect.top + height;
 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom);
 }
 /**
 * Handles scrolling in response to a "home/end" shortcut press. This
 * method will scroll the view to the top or bottom and give the focus
 * to the topmost/bottommost component in the new visible area. If no
 * component is a good candidate for focus, this scrollview reclaims the
 * focus.
 *
 * @param direction the scroll direction: {@link View#FOCUS_UP}
 * to go the top of the view or
 * {@link View#FOCUS_DOWN} to go the bottom
 * @return true if the key event is consumed by this method, false otherwise
 */
 public boolean fullScroll(int direction) {
 boolean down = direction == View.FOCUS_DOWN;
 int height = getHeight();
 mTempRect.top = 0;
 mTempRect.bottom = height;
 if (down) {
 int count = getChildCount();
 if (count > 0) {
 View view = getChildAt(count - 1);
 LayoutParams lp = (LayoutParams) view.getLayoutParams();
 mTempRect.bottom = view.getBottom() + lp.bottomMargin + getPaddingBottom();
 mTempRect.top = mTempRect.bottom - height;
 }
 }
 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom);
 }
 /**
 * Scrolls the view to make the area defined by <code>top</code> and
 * <code>bottom</code> visible. This method attempts to give the focus
 * to a component visible in this area. If no component can be focused in
 * the new visible area, the focus is reclaimed by this ScrollView.
 *
 * @param direction the scroll direction: {@link View#FOCUS_UP}
 * to go upward, {@link View#FOCUS_DOWN} to downward
 * @param top the top offset of the new area to be made visible
 * @param bottom the bottom offset of the new area to be made visible
 * @return true if the key event is consumed by this method, false otherwise
 */
 private boolean scrollAndFocus(int direction, int top, int bottom) {
 boolean handled = true;
 int height = getHeight();
 int containerTop = getScrollY();
 int containerBottom = containerTop + height;
 boolean up = direction == View.FOCUS_UP;
 View newFocused = findFocusableViewInBounds(up, top, bottom);
 if (newFocused == null) {
 newFocused = this;
 }
 if (top >= containerTop && bottom <= containerBottom) {
 handled = false;
 } else {
 int delta = up ? (top - containerTop) : (bottom - containerBottom);
 scrollBy(delta, 0, ViewCompat.TYPE_NON_TOUCH, true);
 }
 if (newFocused != findFocus()) newFocused.requestFocus(direction);
 return handled;
 }
 /**
 * Handle scrolling in response to an up or down arrow click.
 *
 * @param direction The direction corresponding to the arrow key that was
 * pressed
 * @return True if we consumed the event, false otherwise
 */
 public boolean arrowScroll(int direction) {
 View currentFocused = findFocus();
 if (currentFocused == this) currentFocused = null;
 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction);
 final int maxJump = getMaxScrollAmount();
 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) {
 nextFocused.getDrawingRect(mTempRect);
 offsetDescendantRectToMyCoords(nextFocused, mTempRect);
 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect);
 scrollBy(scrollDelta, 0, ViewCompat.TYPE_NON_TOUCH, true);
 nextFocused.requestFocus(direction);
 } else {
 // no new focus
 int scrollDelta = maxJump;
 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) {
 scrollDelta = getScrollY();
 } else if (direction == View.FOCUS_DOWN) {
 if (getChildCount() > 0) {
 View child = getChildAt(0);
 LayoutParams lp = (LayoutParams) child.getLayoutParams();
 int daBottom = child.getBottom() + lp.bottomMargin;
 int screenBottom = getScrollY() + getHeight() - getPaddingBottom();
 scrollDelta = Math.min(daBottom - screenBottom, maxJump);
 }
 }
 if (scrollDelta == 0) {
 return false;
 }
 int finalScrollDelta = direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta;
 scrollBy(finalScrollDelta, 0, ViewCompat.TYPE_NON_TOUCH, true);
 }
 if (currentFocused != null && currentFocused.isFocused()
 && isOffScreen(currentFocused)) {
 // previously focused item still has focus and is off screen, give
 // it up (take it back to ourselves)
 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are
 // sure to
 // get it)
 final int descendantFocusability = getDescendantFocusability(); // save
 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS);
 requestFocus();
 setDescendantFocusability(descendantFocusability); // restore
 }
 return true;
 }
 /**
 * @return whether the descendant of this scroll view is scrolled off
 * screen.
 */
 private boolean isOffScreen(View descendant) {
 return !isWithinDeltaOfScreen(descendant, 0, getHeight());
 }
 /**
 * @return whether the descendant of this scroll view is within delta
 * pixels of being on the screen.
 */
 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) {
 descendant.getDrawingRect(mTempRect);
 offsetDescendantRectToMyCoords(descendant, mTempRect);
 return (mTempRect.bottom + delta) >= getScrollY()
 && (mTempRect.top - delta) <= (getScrollY() + height);
 }
 /**
 * Smooth scroll by a Y delta
 *
 * @param delta the number of pixels to scroll by on the Y axis
 */
 private void doScrollY(int delta) {
 if (delta != 0) {
 if (mSmoothScrollingEnabled) {
 smoothScrollBy(0, delta);
 } else {
 scrollBy(0, delta);
 }
 }
 }
 /**
 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately.
 *
 * @param dx the number of pixels to scroll by on the X axis
 * @param dy the number of pixels to scroll by on the Y axis
 */
 public final void smoothScrollBy(int dx, int dy) {
 smoothScrollBy(dx, dy, DEFAULT_SMOOTH_SCROLL_DURATION, false);
 }
 /**
 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately.
 *
 * @param dx the number of pixels to scroll by on the X axis
 * @param dy the number of pixels to scroll by on the Y axis
 * @param scrollDurationMs the duration of the smooth scroll operation in milliseconds
 */
 public final void smoothScrollBy(int dx, int dy, int scrollDurationMs) {
 smoothScrollBy(dx, dy, scrollDurationMs, false);
 }
 /**
 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately.
 *
 * @param dx the number of pixels to scroll by on the X axis
 * @param dy the number of pixels to scroll by on the Y axis
 * @param scrollDurationMs the duration of the smooth scroll operation in milliseconds
 * @param withNestedScrolling whether to include nested scrolling operations.
 */
 private void smoothScrollBy(int dx, int dy, int scrollDurationMs, boolean withNestedScrolling) {
 if (getChildCount() == 0) {
 // Nothing to do.
 return;
 }
 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll;
 if (duration > ANIMATED_SCROLL_GAP) {
 View child = getChildAt(0);
 LayoutParams lp = (LayoutParams) child.getLayoutParams();
 int childSize = child.getHeight() + lp.topMargin + lp.bottomMargin;
 int parentSpace = getHeight() - getPaddingTop() - getPaddingBottom();
 final int scrollY = getScrollY();
 final int maxY = Math.max(0, childSize - parentSpace);
 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY;
 mScroller.startScroll(getScrollX(), scrollY, 0, dy, scrollDurationMs);
 runAnimatedScroll(withNestedScrolling);
 } else {
 if (!mScroller.isFinished()) {
 abortAnimatedScroll();
 }
 scrollBy(dx, dy);
 }
 mLastScroll = AnimationUtils.currentAnimationTimeMillis();
 }
 /**
 * Like {@link #scrollTo}, but scroll smoothly instead of immediately.
 *
 * @param x the position where to scroll on the X axis
 * @param y the position where to scroll on the Y axis
 */
 public final void smoothScrollTo(int x, int y) {
 smoothScrollTo(x, y, DEFAULT_SMOOTH_SCROLL_DURATION, false);
 }
 /**
 * Like {@link #scrollTo}, but scroll smoothly instead of immediately.
 *
 * @param x the position where to scroll on the X axis
 * @param y the position where to scroll on the Y axis
 * @param scrollDurationMs the duration of the smooth scroll operation in milliseconds
 */
 public final void smoothScrollTo(int x, int y, int scrollDurationMs) {
 smoothScrollTo(x, y, scrollDurationMs, false);
 }
 /**
 * Like {@link #scrollTo}, but scroll smoothly instead of immediately.
 *
 * @param x the position where to scroll on the X axis
 * @param y the position where to scroll on the Y axis
 * @param withNestedScrolling whether to include nested scrolling operations.
 */
 // This should be considered private, it is package private to avoid a synthetic ancestor.
 @SuppressWarnings("SameParameterValue")
 void smoothScrollTo(int x, int y, boolean withNestedScrolling) {
 smoothScrollTo(x, y, DEFAULT_SMOOTH_SCROLL_DURATION, withNestedScrolling);
 }
 /**
 * Like {@link #scrollTo}, but scroll smoothly instead of immediately.
 *
 * @param x the position where to scroll on the X axis
 * @param y the position where to scroll on the Y axis
 * @param scrollDurationMs the duration of the smooth scroll operation in milliseconds
 * @param withNestedScrolling whether to include nested scrolling operations.
 */
 // This should be considered private, it is package private to avoid a synthetic ancestor.
 void smoothScrollTo(int x, int y, int scrollDurationMs, boolean withNestedScrolling) {
 smoothScrollBy(x - getScrollX(), y - getScrollY(), scrollDurationMs, withNestedScrolling);
 }
 /**
 * The scroll range of a scroll view is the overall height of all of its
 * children.
 */
 @RestrictTo(LIBRARY_GROUP_PREFIX)
 @Override
 public int computeVerticalScrollRange() {
 final int count = getChildCount();
 final int parentSpace = getHeight() - getPaddingBottom() - getPaddingTop();
 if (count == 0) {
 return parentSpace;
 }
 View child = getChildAt(0);
 LayoutParams lp = (LayoutParams) child.getLayoutParams();
 int scrollRange = child.getBottom() + lp.bottomMargin;
 final int scrollY = getScrollY();
 final int overscrollBottom = Math.max(0, scrollRange - parentSpace);
 if (scrollY < 0) {
 scrollRange -= scrollY;
 } else if (scrollY > overscrollBottom) {
 scrollRange += scrollY - overscrollBottom;
 }
 return scrollRange;
 }
 @RestrictTo(LIBRARY_GROUP_PREFIX)
 @Override
 public int computeVerticalScrollOffset() {
 return Math.max(0, super.computeVerticalScrollOffset());
 }
 @RestrictTo(LIBRARY_GROUP_PREFIX)
 @Override
 public int computeVerticalScrollExtent() {
 return super.computeVerticalScrollExtent();
 }
 @RestrictTo(LIBRARY_GROUP_PREFIX)
 @Override
 public int computeHorizontalScrollRange() {
 return super.computeHorizontalScrollRange();
 }
 @RestrictTo(LIBRARY_GROUP_PREFIX)
 @Override
 public int computeHorizontalScrollOffset() {
 return super.computeHorizontalScrollOffset();
 }
 @RestrictTo(LIBRARY_GROUP_PREFIX)
 @Override
 public int computeHorizontalScrollExtent() {
 return super.computeHorizontalScrollExtent();
 }
 @Override
 protected void measureChild(@NonNull View child, int parentWidthMeasureSpec,
 int parentHeightMeasureSpec) {
 ViewGroup.LayoutParams lp = child.getLayoutParams();
 int childWidthMeasureSpec;
 int childHeightMeasureSpec;
 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, getPaddingLeft()
 + getPaddingRight(), lp.width);
 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
 child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
 }
 @Override
 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed,
 int parentHeightMeasureSpec, int heightUsed) {
 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec,
 getPaddingLeft() + getPaddingRight() + lp.leftMargin + lp.rightMargin
 + widthUsed, lp.width);
 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(
 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED);
 child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
 }
 @Override
 public void computeScroll() {
 if (mScroller.isFinished()) {
 return;
 }
 mScroller.computeScrollOffset();
 final int y = mScroller.getCurrY();
 int unconsumed = consumeFlingInVerticalStretch(y - mLastScrollerY);
 mLastScrollerY = y;
 // Nested Scrolling Pre Pass
 mScrollConsumed[1] = 0;
 dispatchNestedPreScroll(0, unconsumed, mScrollConsumed, null,
 ViewCompat.TYPE_NON_TOUCH);
 unconsumed -= mScrollConsumed[1];
 final int range = getScrollRange();
 if (unconsumed != 0) {
 // Internal Scroll
 final int oldScrollY = getScrollY();
 overScrollByCompat(0, unconsumed, getScrollX(), oldScrollY, 0, range, 0, 0, false);
 final int scrolledByMe = getScrollY() - oldScrollY;
 unconsumed -= scrolledByMe;
 // Nested Scrolling Post Pass
 mScrollConsumed[1] = 0;
 dispatchNestedScroll(0, scrolledByMe, 0, unconsumed, mScrollOffset,
 ViewCompat.TYPE_NON_TOUCH, mScrollConsumed);
 unconsumed -= mScrollConsumed[1];
 }
 if (unconsumed != 0) {
 final int mode = getOverScrollMode();
 final boolean canOverscroll = mode == OVER_SCROLL_ALWAYS
 || (mode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0);
 if (canOverscroll) {
 if (unconsumed < 0) {
 if (mEdgeGlowTop.isFinished()) {
 mEdgeGlowTop.onAbsorb((int) mScroller.getCurrVelocity());
 }
 } else {
 if (mEdgeGlowBottom.isFinished()) {
 mEdgeGlowBottom.onAbsorb((int) mScroller.getCurrVelocity());
 }
 }
 }
 abortAnimatedScroll();
 }
 if (!mScroller.isFinished()) {
 postInvalidateOnAnimation();
 } else {
 stopNestedScroll(ViewCompat.TYPE_NON_TOUCH);
 }
 }
 /**
 * If either of the vertical edge glows are currently active, this consumes part or all of
 * deltaY on the edge glow.
 *
 * @param deltaY The pointer motion, in pixels, in the vertical direction, positive
 * for moving down and negative for moving up.
 * @param x The vertical position of the pointer.
 * @return The amount of <code>deltaY</code> that has been consumed by the
 * edge glow.
 */
 private int releaseVerticalGlow(int deltaY, float x) {
 // First allow releasing existing overscroll effect:
 float consumed = 0;
 float displacement = x / getWidth();
 float pullDistance = (float) deltaY / getHeight();
 if (EdgeEffectCompat.getDistance(mEdgeGlowTop) != 0) {
 consumed = -EdgeEffectCompat.onPullDistance(mEdgeGlowTop, -pullDistance, displacement);
 if (EdgeEffectCompat.getDistance(mEdgeGlowTop) == 0) {
 mEdgeGlowTop.onRelease();
 }
 } else if (EdgeEffectCompat.getDistance(mEdgeGlowBottom) != 0) {
 consumed = EdgeEffectCompat.onPullDistance(mEdgeGlowBottom, pullDistance,
 1 - displacement);
 if (EdgeEffectCompat.getDistance(mEdgeGlowBottom) == 0) {
 mEdgeGlowBottom.onRelease();
 }
 }
 int pixelsConsumed = Math.round(consumed * getHeight());
 if (pixelsConsumed != 0) {
 invalidate();
 }
 return pixelsConsumed;
 }
 private void runAnimatedScroll(boolean participateInNestedScrolling) {
 if (participateInNestedScrolling) {
 startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL, ViewCompat.TYPE_NON_TOUCH);
 } else {
 stopNestedScroll(ViewCompat.TYPE_NON_TOUCH);
 }
 mLastScrollerY = getScrollY();
 postInvalidateOnAnimation();
 }
 private void abortAnimatedScroll() {
 mScroller.abortAnimation();
 stopNestedScroll(ViewCompat.TYPE_NON_TOUCH);
 }
 /**
 * Scrolls the view to the given child.
 *
 * @param child the View to scroll to
 */
 private void scrollToChild(View child) {
 child.getDrawingRect(mTempRect);
 /* Offset from child's local coordinates to ScrollView coordinates */
 offsetDescendantRectToMyCoords(child, mTempRect);
 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect);
 if (scrollDelta != 0) {
 scrollBy(0, scrollDelta);
 }
 }
 /**
 * If rect is off screen, scroll just enough to get it (or at least the
 * first screen size chunk of it) on screen.
 *
 * @param rect The rectangle.
 * @param immediate True to scroll immediately without animation
 * @return true if scrolling was performed
 */
 private boolean scrollToChildRect(Rect rect, boolean immediate) {
 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect);
 final boolean scroll = delta != 0;
 if (scroll) {
 if (immediate) {
 scrollBy(0, delta);
 } else {
 smoothScrollBy(0, delta);
 }
 }
 return scroll;
 }
 /**
 * Compute the amount to scroll in the Y direction in order to get
 * a rectangle completely on the screen (or, if taller than the screen,
 * at least the first screen size chunk of it).
 *
 * @param rect The rect.
 * @return The scroll delta.
 */
 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) {
 if (getChildCount() == 0) return 0;
 int height = getHeight();
 int screenTop = getScrollY();
 int screenBottom = screenTop + height;
 int actualScreenBottom = screenBottom;
 int fadingEdge = getVerticalFadingEdgeLength();
 // TODO: screenTop should be incremented by fadingEdge * getTopFadingEdgeStrength (but for
 // the target scroll distance).
 // leave room for top fading edge as long as rect isn't at very top
 if (rect.top > 0) {
 screenTop += fadingEdge;
 }
 // TODO: screenBottom should be decremented by fadingEdge * getBottomFadingEdgeStrength (but
 // for the target scroll distance).
 // leave room for bottom fading edge as long as rect isn't at very bottom
 View child = getChildAt(0);
 final LayoutParams lp = (LayoutParams) child.getLayoutParams();
 if (rect.bottom < child.getHeight() + lp.topMargin + lp.bottomMargin) {
 screenBottom -= fadingEdge;
 }
 int scrollYDelta = 0;
 if (rect.bottom > screenBottom && rect.top > screenTop) {
 // need to move down to get it in view: move down just enough so
 // that the entire rectangle is in view (or at least the first
 // screen size chunk).
 if (rect.height() > height) {
 // just enough to get screen size chunk on
 scrollYDelta += (rect.top - screenTop);
 } else {
 // get entire rect at bottom of screen
 scrollYDelta += (rect.bottom - screenBottom);
 }
 // make sure we aren't scrolling beyond the end of our content
 int bottom = child.getBottom() + lp.bottomMargin;
 int distanceToBottom = bottom - actualScreenBottom;
 scrollYDelta = Math.min(scrollYDelta, distanceToBottom);
 } else if (rect.top < screenTop && rect.bottom < screenBottom) {
 // need to move up to get it in view: move up just enough so that
 // entire rectangle is in view (or at least the first screen
 // size chunk of it).
 if (rect.height() > height) {
 // screen size chunk
 scrollYDelta -= (screenBottom - rect.bottom);
 } else {
 // entire rect at top
 scrollYDelta -= (screenTop - rect.top);
 }
 // make sure we aren't scrolling any further than the top our content
 scrollYDelta = Math.max(scrollYDelta, -getScrollY());
 }
 return scrollYDelta;
 }
 @Override
 public void requestChildFocus(View child, View focused) {
 if (!mIsLayoutDirty) {
 scrollToChild(focused);
 } else {
 // The child may not be laid out yet, we can't compute the scroll yet
 mChildToScrollTo = focused;
 }
 super.requestChildFocus(child, focused);
 }
 /**
 * When looking for focus in children of a scroll view, need to be a little
 * more careful not to give focus to something that is scrolled off screen.
 *
 * This is more expensive than the default {@link ViewGroup}
 * implementation, otherwise this behavior might have been made the default.
 */
 @Override
 protected boolean onRequestFocusInDescendants(int direction,
 Rect previouslyFocusedRect) {
 // convert from forward / backward notation to up / down / left / right
 // (ugh).
 if (direction == View.FOCUS_FORWARD) {
 direction = View.FOCUS_DOWN;
 } else if (direction == View.FOCUS_BACKWARD) {
 direction = View.FOCUS_UP;
 }
 final View nextFocus = previouslyFocusedRect == null
 ? FocusFinder.getInstance().findNextFocus(this, null, direction)
 : FocusFinder.getInstance().findNextFocusFromRect(
 this, previouslyFocusedRect, direction);
 if (nextFocus == null) {
 return false;
 }
 if (isOffScreen(nextFocus)) {
 return false;
 }
 return nextFocus.requestFocus(direction, previouslyFocusedRect);
 }
 @Override
 public boolean requestChildRectangleOnScreen(@NonNull View child, Rect rectangle,
 boolean immediate) {
 // offset into coordinate space of this scroll view
 rectangle.offset(child.getLeft() - child.getScrollX(),
 child.getTop() - child.getScrollY());
 return scrollToChildRect(rectangle, immediate);
 }
 @Override
 public void requestLayout() {
 mIsLayoutDirty = true;
 super.requestLayout();
 }
 @Override
 protected void onLayout(boolean changed, int l, int t, int r, int b) {
 super.onLayout(changed, l, t, r, b);
 mIsLayoutDirty = false;
 // Give a child focus if it needs it
 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) {
 scrollToChild(mChildToScrollTo);
 }
 mChildToScrollTo = null;
 if (!mIsLaidOut) {
 // If there is a saved state, scroll to the position saved in that state.
 if (mSavedState != null) {
 scrollTo(getScrollX(), mSavedState.scrollPosition);
 mSavedState = null;
 } // mScrollY default value is "0"
 // Make sure current scrollY position falls into the scroll range. If it doesn't,
 // scroll such that it does.
 int childSize = 0;
 if (getChildCount() > 0) {
 View child = getChildAt(0);
 LayoutParams lp = (LayoutParams) child.getLayoutParams();
 childSize = child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;
 }
 int parentSpace = b - t - getPaddingTop() - getPaddingBottom();
 int currentScrollY = getScrollY();
 int newScrollY = clamp(currentScrollY, parentSpace, childSize);
 if (newScrollY != currentScrollY) {
 scrollTo(getScrollX(), newScrollY);
 }
 }
 // Calling this with the present values causes it to re-claim them
 scrollTo(getScrollX(), getScrollY());
 mIsLaidOut = true;
 }
 @Override
 public void onAttachedToWindow() {
 super.onAttachedToWindow();
 mIsLaidOut = false;
 }
 @Override
 protected void onSizeChanged(int w, int h, int oldw, int oldh) {
 super.onSizeChanged(w, h, oldw, oldh);
 View currentFocused = findFocus();
 if (null == currentFocused || this == currentFocused) {
 return;
 }
 // If the currently-focused view was visible on the screen when the
 // screen was at the old height, then scroll the screen to make that
 // view visible with the new screen height.
 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) {
 currentFocused.getDrawingRect(mTempRect);
 offsetDescendantRectToMyCoords(currentFocused, mTempRect);
 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect);
 doScrollY(scrollDelta);
 }
 }
 /**
 * Return true if child is a descendant of parent, (or equal to the parent).
 */
 private static boolean isViewDescendantOf(View child, View parent) {
 if (child == parent) {
 return true;
 }
 final ViewParent theParent = child.getParent();
 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent);
 }
 /**
 * Fling the scroll view
 *
 * @param velocityY The initial velocity in the Y direction. Positive
 * numbers mean that the finger/cursor is moving down the screen,
 * which means we want to scroll towards the top.
 */
 public void fling(int velocityY) {
 if (getChildCount() > 0) {
 mScroller.fling(getScrollX(), getScrollY(), // start
 0, velocityY, // velocities
 0, 0, // x
 Integer.MIN_VALUE, Integer.MAX_VALUE, // y
 0, 0); // overscroll
 runAnimatedScroll(true);
 }
 }
 /**
 * {@inheritDoc}
 *
 * This version also clamps the scrolling to the bounds of our child.
 */
 @Override
 public void scrollTo(int x, int y) {
 // we rely on the fact the View.scrollBy calls scrollTo.
 if (getChildCount() > 0) {
 View child = getChildAt(0);
 final LayoutParams lp = (LayoutParams) child.getLayoutParams();
 int parentSpaceHorizontal = getWidth() - getPaddingLeft() - getPaddingRight();
 int childSizeHorizontal = child.getWidth() + lp.leftMargin + lp.rightMargin;
 int parentSpaceVertical = getHeight() - getPaddingTop() - getPaddingBottom();
 int childSizeVertical = child.getHeight() + lp.topMargin + lp.bottomMargin;
 x = clamp(x, parentSpaceHorizontal, childSizeHorizontal);
 y = clamp(y, parentSpaceVertical, childSizeVertical);
 if (x != getScrollX() || y != getScrollY()) {
 super.scrollTo(x, y);
 }
 }
 }
 @Override
 public void draw(@NonNull Canvas canvas) {
 super.draw(canvas);
 final int scrollY = getScrollY();
 if (!mEdgeGlowTop.isFinished()) {
 final int restoreCount = canvas.save();
 int width = getWidth();
 int height = getHeight();
 int xTranslation = 0;
 int yTranslation = Math.min(0, scrollY);
 if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP
 || Api21Impl.getClipToPadding(this)) {
 width -= getPaddingLeft() + getPaddingRight();
 xTranslation += getPaddingLeft();
 }
 if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP
 && Api21Impl.getClipToPadding(this)) {
 height -= getPaddingTop() + getPaddingBottom();
 yTranslation += getPaddingTop();
 }
 canvas.translate(xTranslation, yTranslation);
 mEdgeGlowTop.setSize(width, height);
 if (mEdgeGlowTop.draw(canvas)) {
 postInvalidateOnAnimation();
 }
 canvas.restoreToCount(restoreCount);
 }
 if (!mEdgeGlowBottom.isFinished()) {
 final int restoreCount = canvas.save();
 int width = getWidth();
 int height = getHeight();
 int xTranslation = 0;
 int yTranslation = Math.max(getScrollRange(), scrollY) + height;
 if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP
 || Api21Impl.getClipToPadding(this)) {
 width -= getPaddingLeft() + getPaddingRight();
 xTranslation += getPaddingLeft();
 }
 if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP
 && Api21Impl.getClipToPadding(this)) {
 height -= getPaddingTop() + getPaddingBottom();
 yTranslation -= getPaddingBottom();
 }
 canvas.translate(xTranslation - width, yTranslation);
 canvas.rotate(180, width, 0);
 mEdgeGlowBottom.setSize(width, height);
 if (mEdgeGlowBottom.draw(canvas)) {
 postInvalidateOnAnimation();
 }
 canvas.restoreToCount(restoreCount);
 }
 }
 private static int clamp(int n, int my, int child) {
 if (my >= child || n < 0) {
 /* my >= child is this case:
 * |--------------- me ---------------|
 * |------ child ------|
 * or
 * |--------------- me ---------------|
 * |------ child ------|
 * or
 * |--------------- me ---------------|
 * |------ child ------|
 *
 * n < 0 is this case:
 * |------ me ------|
 * |-------- child --------|
 * |-- mScrollX --|
 */
 return 0;
 }
 if ((my + n) > child) {
 /* this case:
 * |------ me ------|
 * |------ child ------|
 * |-- mScrollX --|
 */
 return child - my;
 }
 return n;
 }
 @Override
 protected void onRestoreInstanceState(Parcelable state) {
 if (!(state instanceof SavedState)) {
 super.onRestoreInstanceState(state);
 return;
 }
 SavedState ss = (SavedState) state;
 super.onRestoreInstanceState(ss.getSuperState());
 mSavedState = ss;
 requestLayout();
 }
 @NonNull
 @Override
 protected Parcelable onSaveInstanceState() {
 Parcelable superState = super.onSaveInstanceState();
 SavedState ss = new SavedState(superState);
 ss.scrollPosition = getScrollY();
 return ss;
 }
 static class SavedState extends BaseSavedState {
 public int scrollPosition;
 SavedState(Parcelable superState) {
 super(superState);
 }
 SavedState(Parcel source) {
 super(source);
 scrollPosition = source.readInt();
 }
 @Override
 public void writeToParcel(Parcel dest, int flags) {
 super.writeToParcel(dest, flags);
 dest.writeInt(scrollPosition);
 }
 @NonNull
 @Override
 public String toString() {
 return "HorizontalScrollView.SavedState{"
 + Integer.toHexString(System.identityHashCode(this))
 + " scrollPosition=" + scrollPosition + "}";
 }
 public static final Creator<SavedState> CREATOR =
 new Creator<SavedState>() {
 @Override
 public SavedState createFromParcel(Parcel in) {
 return new SavedState(in);
 }
 @Override
 public SavedState[] newArray(int size) {
 return new SavedState[size];
 }
 };
 }
 static class AccessibilityDelegate extends AccessibilityDelegateCompat {
 @Override
 public boolean performAccessibilityAction(View host, int action, Bundle arguments) {
 if (super.performAccessibilityAction(host, action, arguments)) {
 return true;
 }
 final NestedScrollView nsvHost = (NestedScrollView) host;
 if (!nsvHost.isEnabled()) {
 return false;
 }
 int height = nsvHost.getHeight();
 Rect rect = new Rect();
 // Gets the visible rect on the screen except for the rotation or scale cases which
 // might affect the result.
 if (nsvHost.getMatrix().isIdentity() && nsvHost.getGlobalVisibleRect(rect)) {
 height = rect.height();
 }
 switch (action) {
 case AccessibilityNodeInfoCompat.ACTION_SCROLL_FORWARD:
 case android.R.id.accessibilityActionScrollDown: {
 final int viewportHeight = height - nsvHost.getPaddingBottom()
 - nsvHost.getPaddingTop();
 final int targetScrollY = Math.min(nsvHost.getScrollY() + viewportHeight,
 nsvHost.getScrollRange());
 if (targetScrollY != nsvHost.getScrollY()) {
 nsvHost.smoothScrollTo(0, targetScrollY, true);
 return true;
 }
 }
 return false;
 case AccessibilityNodeInfoCompat.ACTION_SCROLL_BACKWARD:
 case android.R.id.accessibilityActionScrollUp: {
 final int viewportHeight = height - nsvHost.getPaddingBottom()
 - nsvHost.getPaddingTop();
 final int targetScrollY = Math.max(nsvHost.getScrollY() - viewportHeight, 0);
 if (targetScrollY != nsvHost.getScrollY()) {
 nsvHost.smoothScrollTo(0, targetScrollY, true);
 return true;
 }
 }
 return false;
 }
 return false;
 }
 @Override
 public void onInitializeAccessibilityNodeInfo(View host, AccessibilityNodeInfoCompat info) {
 super.onInitializeAccessibilityNodeInfo(host, info);
 final NestedScrollView nsvHost = (NestedScrollView) host;
 info.setClassName(ScrollView.class.getName());
 if (nsvHost.isEnabled()) {
 final int scrollRange = nsvHost.getScrollRange();
 if (scrollRange > 0) {
 info.setScrollable(true);
 if (nsvHost.getScrollY() > 0) {
 info.addAction(AccessibilityNodeInfoCompat.AccessibilityActionCompat
 .ACTION_SCROLL_BACKWARD);
 info.addAction(AccessibilityNodeInfoCompat.AccessibilityActionCompat
 .ACTION_SCROLL_UP);
 }
 if (nsvHost.getScrollY() < scrollRange) {
 info.addAction(AccessibilityNodeInfoCompat.AccessibilityActionCompat
 .ACTION_SCROLL_FORWARD);
 info.addAction(AccessibilityNodeInfoCompat.AccessibilityActionCompat
 .ACTION_SCROLL_DOWN);
 }
 }
 }
 }
 @Override
 public void onInitializeAccessibilityEvent(View host, AccessibilityEvent event) {
 super.onInitializeAccessibilityEvent(host, event);
 final NestedScrollView nsvHost = (NestedScrollView) host;
 event.setClassName(ScrollView.class.getName());
 final boolean scrollable = nsvHost.getScrollRange() > 0;
 event.setScrollable(scrollable);
 event.setScrollX(nsvHost.getScrollX());
 event.setScrollY(nsvHost.getScrollY());
 AccessibilityRecordCompat.setMaxScrollX(event, nsvHost.getScrollX());
 AccessibilityRecordCompat.setMaxScrollY(event, nsvHost.getScrollRange());
 }
 }
 class DifferentialMotionFlingTargetImpl implements DifferentialMotionFlingTarget {
 @Override
 public boolean startDifferentialMotionFling(float velocity) {
 if (velocity == 0) {
 return false;
 }
 stopDifferentialMotionFling();
 fling((int) velocity);
 return true;
 }
 @Override
 public void stopDifferentialMotionFling() {
 mScroller.abortAnimation();
 }
 @Override
 public float getScaledScrollFactor() {
 return -getVerticalScrollFactorCompat();
 }
 }
 @RequiresApi(21)
 static class Api21Impl {
 private Api21Impl() {
 // This class is not instantiable.
 }
 @DoNotInline
 static boolean getClipToPadding(ViewGroup viewGroup) {
 return viewGroup.getClipToPadding();
 }
 }
}
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