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  • Android--ScrollView边界回弹效果

    /*
     * 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.
     */
    
    import android.content.Context;
    import android.graphics.Color;
    import android.graphics.Rect;
    import android.util.AttributeSet;
    import android.util.DisplayMetrics;
    import android.view.FocusFinder;
    import android.view.KeyEvent;
    import android.view.LayoutInflater;
    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.animation.AnimationUtils;
    import android.view.animation.OvershootInterpolator;
    import android.widget.FrameLayout;
    import android.widget.Scroller;
    import android.view.View.OnTouchListener;
    
    import java.lang.reflect.Field;
    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.
     * <p>
     * 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.
     * <p>
     * ScrollView only supports vertical scrolling.
     */
    public class OverScrollView extends FrameLayout implements OnTouchListener
    {
    
        static final int ANIMATED_SCROLL_GAP = 250;
    
        static final float MAX_SCROLL_FACTOR = 0.5f;
        static final float OVERSHOOT_TENSION = 0.75f;
    
        private long mLastScroll;
    
        private final Rect mTempRect = new Rect();
        private Scroller mScroller;
    
        protected Context mContext;
    
        Field mScrollYField;
        Field mScrollXField;
    
        boolean hasFailedObtainingScrollFields;
        int prevScrollY;
        boolean isInFlingMode = false;
    
        DisplayMetrics metrics;
        LayoutInflater inflater;
        protected View child;
    
        private Runnable overScrollerSpringbackTask;
    
        /**
         * Flag to indicate that we are moving focus ourselves. This is so the code
         * that watches for focus changes initiated outside this ScrollView knows
         * that it does not have to do anything.
         */
        private boolean mScrollViewMovedFocus;
    
        /**
         * Position of the last motion event.
         */
        private float 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.
         */
        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;
    
        /**
         * Sentinel value for no current active pointer. Used by
         * {@link #mActivePointerId}.
         */
        private static final int INVALID_POINTER = -1;
    
        private OnScrollChangedListener onScrollChangedListener;
    
        public OverScrollView(Context context)
        {
            this(context, null);
        }
    
        public OverScrollView(Context context, AttributeSet attrs)
        {
    
            this(context, attrs, 0);
        }
    
        public OverScrollView(Context context, AttributeSet attrs, int defStyle)
        {
            super(context, attrs, defStyle);
            mContext = context;
    
            initScrollView();
            setFillViewport(true);
            initBounce();
        }
    
        private void initBounce()
        {
            metrics = this.mContext.getResources().getDisplayMetrics();
    
            // init the bouncy scroller, and make sure the layout is being drawn
            // after the top padding
            mScroller = new Scroller(getContext(), new OvershootInterpolator(OVERSHOOT_TENSION));
            overScrollerSpringbackTask = new Runnable()
            {
                @Override
                public void run()
                {
                    // scroll till after the padding
                    mScroller.computeScrollOffset();
                    scrollTo(0, mScroller.getCurrY());
    
                    if (!mScroller.isFinished())
                    {
                        post(this);
                    }
                }
            };
            prevScrollY = getPaddingTop();
    
            try
            {
                mScrollXField = View.class.getDeclaredField("mScrollX");
                mScrollYField = View.class.getDeclaredField("mScrollY");
    
            }
            catch (Exception e)
            {
                hasFailedObtainingScrollFields = true;
            }
        }
    
        private void SetScrollY(int value)
        {
            if (mScrollYField != null)
            {
                try
                {
                    mScrollYField.setInt(this, value);
                }
                catch (Exception e)
                {
                }
            }
        }
    
        private void SetScrollX(int value)
        {
            if (mScrollXField != null)
            {
                try
                {
                    mScrollXField.setInt(this, value);
                }
                catch (Exception e)
                {
                }
            }
        }
    
        public void initChildPointer()
        {
            child = getChildAt(0);
            child.setPadding(0, 1500, 0, 1500);
    
        }
    
        @Override
        protected float getTopFadingEdgeStrength()
        {
            if (getChildCount() == 0)
            {
                return 0.0f;
            }
    
            final int length = getVerticalFadingEdgeLength();
            if (getScrollY() < length)
            {
                return getScrollY() / (float) length;
            }
    
            return 1.0f;
        }
    
        @Override
        protected float getBottomFadingEdgeStrength()
        {
            if (getChildCount() == 0)
            {
                return 0.0f;
            }
    
            final int length = getVerticalFadingEdgeLength();
            final int bottomEdge = getHeight() - getPaddingBottom();
            final int span = getChildAt(0).getBottom() - 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 * (getBottom() - getTop()));
        }
    
        private void initScrollView()
        {
            mScroller = new Scroller(getContext());
            setFocusable(true);
            setDescendantFocusability(FOCUS_AFTER_DESCENDANTS);
            setWillNotDraw(false);
            final ViewConfiguration configuration = ViewConfiguration.get(mContext);
            mTouchSlop = configuration.getScaledTouchSlop();
            mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();
            mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
    
            setOnTouchListener(this);
    
            post(new Runnable()
            {
                public void run()
                {
                    scrollTo(0, child.getPaddingTop());
                }
            });
        }
    
        @Override
        public void addView(View child)
        {
            if (getChildCount() > 0)
            {
                throw new IllegalStateException("ScrollView can host only one direct child");
            }
    
            super.addView(child);
            initChildPointer();
        }
    
        @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);
            initChildPointer();
        }
    
        @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);
            initChildPointer();
        }
    
        @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 + getPaddingTop() + getPaddingBottom();
            }
            return false;
        }
    
        /**
         * Indicates whether this ScrollView's content is stretched to fill the
         * viewport.
         * @return True if the content fills the viewport, false otherwise.
         */
        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.
         */
        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, getPaddingLeft() + getPaddingRight(),
                            lp.width);
                    height -= getPaddingTop();
                    height -= getPaddingBottom();
                    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;
        }
    
        public 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;
        }
    
        @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 float y = ev.getY(pointerIndex);
                final int yDiff = (int) Math.abs(y - mLastMotionY);
                if (yDiff > mTouchSlop)
                {
                    mIsBeingDragged = true;
                    mLastMotionY = y;
                }
                break;
            }
    
            case MotionEvent.ACTION_DOWN:
            {
                final float y = ev.getY();
                if (!inChild((int) ev.getX(), (int) y))
                {
                    mIsBeingDragged = false;
                    break;
                }
    
                /*
                 * Remember location of down touch. ACTION_DOWN always refers to
                 * pointer index 0.
                 */
                mLastMotionY = y;
                mActivePointerId = ev.getPointerId(0);
    
                /*
                 * If being flinged and user touches the screen, initiate drag;
                 * otherwise don't. mScroller.isFinished should be false when being
                 * flinged.
                 */
                mIsBeingDragged = !mScroller.isFinished();
                break;
            }
    
            case MotionEvent.ACTION_CANCEL:
            case MotionEvent.ACTION_UP:
                /* Release the drag */
                mIsBeingDragged = false;
                mActivePointerId = INVALID_POINTER;
                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)
        {
    
            if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0)
            {
                // Don't handle edge touches immediately -- they may actually belong
                // to one of our
                // descendants.
                return false;
            }
    
            if (mVelocityTracker == null)
            {
                mVelocityTracker = VelocityTracker.obtain();
            }
            mVelocityTracker.addMovement(ev);
    
            final int action = ev.getAction();
    
            switch (action & MotionEvent.ACTION_MASK)
            {
            case MotionEvent.ACTION_DOWN:
            {
                final float y = ev.getY();
                if (!(mIsBeingDragged = inChild((int) ev.getX(), (int) y)))
                {
                    return false;
                }
    
                /*
                 * If being flinged and user touches, stop the fling. isFinished
                 * will be false if being flinged.
                 */
                if (!mScroller.isFinished())
                {
                    mScroller.abortAnimation();
                }
    
                // Remember where the motion event started
                mLastMotionY = y;
                mActivePointerId = ev.getPointerId(0);
                break;
            }
            case MotionEvent.ACTION_MOVE:
                if (mIsBeingDragged)
                {
                    // Scroll to follow the motion event
                    final int activePointerIndex = ev.findPointerIndex(mActivePointerId);
                    final float y = ev.getY(activePointerIndex);
                    final int deltaY = (int) (mLastMotionY - y);
                    mLastMotionY = y;
    
                    if (isOverScrolled())
                    {
                        // when overscrolling, move the scroller just half of the
                        // finger movement, to make it feel like a spring...
                        scrollBy(0, deltaY * 2 / 3);
                    }
                    else
                    {
                        scrollBy(0, deltaY);
                    }
                }
                break;
            case MotionEvent.ACTION_UP:
                if (mIsBeingDragged)
                {
                    final VelocityTracker velocityTracker = mVelocityTracker;
                    velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
                    int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId);
    
                    if (getChildCount() > 0 && Math.abs(initialVelocity) > mMinimumVelocity)
                    {
                        fling(-initialVelocity);
                    }
    
                    mActivePointerId = INVALID_POINTER;
                    mIsBeingDragged = false;
    
                    if (mVelocityTracker != null)
                    {
                        mVelocityTracker.recycle();
                        mVelocityTracker = null;
                    }
                }
                break;
            case MotionEvent.ACTION_CANCEL:
                if (mIsBeingDragged && getChildCount() > 0)
                {
                    mActivePointerId = INVALID_POINTER;
                    mIsBeingDragged = false;
                    if (mVelocityTracker != null)
                    {
                        mVelocityTracker.recycle();
                        mVelocityTracker = null;
                    }
                }
                break;
            case MotionEvent.ACTION_POINTER_UP:
                onSecondaryPointerUp(ev);
                break;
            }
            return true;
        }
    
        public boolean isOverScrolled()
        {
            return (getScrollY() < child.getPaddingTop() || getScrollY() > child.getBottom() - child.getPaddingBottom()
                    - getHeight());
        }
    
        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 = ev.getY(newPointerIndex);
                mActivePointerId = ev.getPointerId(newPointerIndex);
                if (mVelocityTracker != null)
                {
                    mVelocityTracker.clear();
                }
            }
        }
    
        /**
         * <p>
         * Finds the next focusable component that fits in this View's bounds
         * (excluding fading edges) pretending that this View's top is located at
         * the parameter top.
         * </p>
         * @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 (the fading edge is assumed to start at this position)
         * @param preferredFocusable the View that has highest priority and will be
         * returned if it is within my bounds (null is valid)
         * @return the next focusable component in the bounds or null if none can be
         * found
         */
        private View findFocusableViewInMyBounds(final boolean topFocus, final int top, View preferredFocusable)
        {
            /*
             * The fading edge's transparent side should be considered for focus
             * since it's mostly visible, so we divide the actual fading edge length
             * by 2.
             */
            final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2;
            final int topWithoutFadingEdge = top + fadingEdgeLength;
            final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength;
    
            if ((preferredFocusable != null) && (preferredFocusable.getTop() < bottomWithoutFadingEdge)
                    && (preferredFocusable.getBottom() > topWithoutFadingEdge))
            {
                return preferredFocusable;
            }
    
            return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, bottomWithoutFadingEdge);
        }
    
        /**
         * <p>
         * Finds the next focusable component that fits in the specified bounds.
         * </p>
         * @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;
        }
    
        /**
         * <p>
         * 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.
         * </p>
         * @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);
        }
    
        /**
         * <p>
         * 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.
         * </p>
         * @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();
                    mTempRect.top = mTempRect.bottom - height;
                }
            }
    
            return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom);
        }
    
        /**
         * <p>
         * 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.
         * </p>
         * @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))
            {
                mScrollViewMovedFocus = true;
                mScrollViewMovedFocus = false;
            }
    
            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();
    
                        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() - getPaddingBottom() - getPaddingTop();
                final int bottom = getChildAt(0).getHeight();
                final int maxY = Math.max(0, bottom - height);
                final int scrollY = getScrollY();
                dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY;
    
                mScroller.startScroll(getScrollX(), scrollY, 0, dy);
                invalidate();
            }
            else
            {
                if (!mScroller.isFinished())
                {
                    mScroller.abortAnimation();
                }
                scrollBy(dx, dy);
            }
            mLastScroll = AnimationUtils.currentAnimationTimeMillis();
        }
    
        public final void smoothScrollToTop()
        {
            smoothScrollTo(0, child.getPaddingTop());
        }
    
        public final void smoothScrollToBottom()
        {
            smoothScrollTo(0, child.getHeight() - child.getPaddingTop() - getHeight());
        }
    
        /**
         * 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 - getScrollX(), y - getScrollY());
        }
    
        /**
         * <p>
         * The scroll range of a scroll view is the overall height of all of its
         * children.
         * </p>
         */
        @Override
        protected int computeVerticalScrollRange()
        {
            final int count = getChildCount();
            final int contentHeight = getHeight() - getPaddingBottom() - getPaddingTop();
            if (count == 0)
            {
                return contentHeight;
            }
    
            return getChildAt(0).getBottom();
        }
    
        @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, 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 android implementation has changed and we cannot obtain mScrollY -
            // The default behavior will be applied by the parent.
            if (hasFailedObtainingScrollFields)
            {
                super.computeScroll();
                return;
            }
    
            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 getScrollX()/Y is different from what the
                // app
                // thinks it is.
                //
                int oldX = getScrollX();
                int oldY = getScrollY();
                int x = mScroller.getCurrX();
                int y = mScroller.getCurrY();
    
                if (getChildCount() > 0)
                {
                    View child = getChildAt(0);
                    x = clamp(x, getWidth() - getPaddingRight() - getPaddingLeft(), child.getWidth());
                    y = clamp(y, getHeight() - getPaddingBottom() - getPaddingTop(), child.getHeight());
                    if (x != oldX || y != oldY)
                    {
                        SetScrollX(x);
                        // mScrollX = x;
                        SetScrollY(y);
                        // mScrollY = y;
                        onScrollChanged(x, y, oldX, oldY);
                    }
                }
                awakenScrollBars();
    
                // Keep on drawing until the animation has finished.
                postInvalidate();
            }
        }
    
        /**
         * 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 (!mScrollViewMovedFocus)
            {
                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 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-clam them
            scrollTo(getScrollX(), getScrollY());
        }
    
        @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);
            }
        }
    
        @Override
        protected void onScrollChanged(int leftOfVisibleView, int topOfVisibleView, int oldLeftOfVisibleView,
                int oldTopOfVisibleView)
        {
            int displayHeight = getHeight();
            int paddingTop = child.getPaddingTop();
            int contentBottom = child.getHeight() - child.getPaddingBottom();
            if (onScrollChangedListener != null)
            {
                onScrollChangedListener.onScrollChanged(leftOfVisibleView, topOfVisibleView, oldLeftOfVisibleView,
                        oldTopOfVisibleView);
            }
            if (isInFlingMode)
            {
    
                if (topOfVisibleView < paddingTop || topOfVisibleView > contentBottom - displayHeight)
                {
                    if (topOfVisibleView < paddingTop)
                    {
                        mScroller.startScroll(0, topOfVisibleView, 0, paddingTop - topOfVisibleView, 1000);
                    }
                    else if (topOfVisibleView > contentBottom - displayHeight)
                    {
                        mScroller.startScroll(0, topOfVisibleView, 0, contentBottom - displayHeight - topOfVisibleView,
                                1000);
                    }
    
                    // Start animation.
                    post(overScrollerSpringbackTask);
                    isInFlingMode = false;
                    return;
    
                }
            }
    
            super.onScrollChanged(leftOfVisibleView, topOfVisibleView, oldLeftOfVisibleView, oldTopOfVisibleView);
        }
    
        /**
         * Return true if child is an descendant of parent, (or equal to the
         * parent).
         */
        private 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() - getPaddingBottom() - getPaddingTop();
                int bottom = getChildAt(0).getHeight();
    
                mScroller.fling(getScrollX(), getScrollY(), 0, velocityY, 0, 0, 0, Math.max(0, bottom - height));
    
                final boolean movingDown = velocityY > 0;
    
                View newFocused = findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus());
                if (newFocused == null)
                {
                    newFocused = this;
                }
    
                if (newFocused != findFocus() && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP))
                {
                    mScrollViewMovedFocus = true;
                    mScrollViewMovedFocus = false;
                }
    
                invalidate();
            }
        }
    
        /**
         * {@inheritDoc}
         * <p>
         * This version also clamps the scrolling to the bounds of our child.
         */
        @Override
        public void scrollTo(int x, int y)
        {
            super.scrollTo(x, y);
            // we rely on the fact the View.scrollBy calls scrollTo.
            if (getChildCount() > 0)
            {
                View child = getChildAt(0);
                x = clamp(x, getWidth() - getPaddingRight() - getPaddingLeft(), child.getWidth());
                y = clamp(y, getHeight() - getPaddingBottom() - getPaddingTop(), child.getHeight());
                if (x != getScrollX() || y != getScrollY())
                {
                    super.scrollTo(x, y);
                }
            }
    
        }
    
        private 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 --------| |-- getScrollX() --|
                 */
                return 0;
            }
            if ((my + n) > child)
            {
                /*
                 * this case: |------ me ------| |------ child ------| |--
                 * getScrollX() --|
                 */
                return child - my;
            }
            return n;
        }
    
        @Override
        public boolean onTouch(View v, MotionEvent event)
        {
            // Stop scrolling calculation.
            mScroller.forceFinished(true);
            // Stop scrolling animation.
            removeCallbacks(overScrollerSpringbackTask);
    
            if (event.getAction() == MotionEvent.ACTION_UP)
            {
                return overScrollView();
            }
    
            else if (event.getAction() == MotionEvent.ACTION_CANCEL)
            {
                return overScrollView();
            }
    
            return false;
        }
    
        private boolean overScrollView()
        {
    
            // The height of scroll view, in pixels
            int displayHeight = getHeight();
            // The top of content view, in pixels.
            int contentTop = child.getPaddingTop();
            // The top of content view, in pixels.
            int contentBottom = child.getHeight() - child.getPaddingBottom();
            // The scrolled top position of scroll view, in pixels.
            int currScrollY = getScrollY();
    
            int scrollBy;
    
            // Scroll to content top
            if (currScrollY < contentTop)
            {
    
                onOverScroll(currScrollY);
                scrollBy = contentTop - currScrollY;
            }
            else if (currScrollY + displayHeight > contentBottom)
            {
                // Scroll to content top
                if (child.getHeight() - child.getPaddingTop() - child.getPaddingBottom() < displayHeight)
                {
    
                    scrollBy = contentTop - currScrollY;
                }
                // Scroll to content bottom
                else
                {
    
                    scrollBy = contentBottom - displayHeight - currScrollY;
                    // Log.d(Definitions.LOG_TAG, "scrollBy=" + scrollBy);
                }
    
                // fire onOverScroll event, and update scrollBy if a loadingView has
                // been added to the scroller.
                scrollBy += onOverScroll(currScrollY);
            }
            // scrolling between the contentTop and contentBottom
            else
            {
                isInFlingMode = true;
                return false;
            }
            mScroller.startScroll(0, currScrollY, 0, scrollBy, 500);
    
            // Start animation.
            post(overScrollerSpringbackTask);
    
            prevScrollY = currScrollY;
    
            // consume(to stop fling)
            return true;
    
        }
    
        protected int onOverScroll(int scrollY)
        {
            return 0;
        }
    
        public void reset()
        {
            if (child != null)
            {
                scrollTo(0, child.getPaddingTop());
            }
            setBackgroundColor(Color.TRANSPARENT);
        }
    
        public int getChildPaddingBotton()
        {
            if (child != null)
            {
                return child.getPaddingBottom();
            }
            return 0;
        }
    
        public boolean isTop()
        {
            return getScrollY() < child.getPaddingTop();
        }
        public boolean isJustTop()
        {
            return getScrollY() <= child.getPaddingTop();
        }
    
        public boolean isBottom()
        {
            return getScrollY() > child.getBottom() - child.getPaddingBottom() - getHeight();
        }
    
        public void setOnScrollChangedListener(OnScrollChangedListener onScrollChangedListener)
        {
            this.onScrollChangedListener = onScrollChangedListener;
        }
    
        public interface OnScrollChangedListener
        {
            public void onScrollChanged(int x, int y, int oldx, int oldy);
    
            public void scrollBottom();
        }
    
    }
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  • 原文地址:https://www.cnblogs.com/crane13/p/4059663.html
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