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  • Android 继承framelayout,实现ScrollView 和 HorizontalScrollView 的效果

    有些项目,需要让控件或者布局进行水平和垂直同时能拖拽,当然,ScrollView 和 HorizontalScrollView 的结合写法是一种写法。但是,这么写用户体验效果不佳,会有迟钝感,因此推荐下面的写法。继承之FrameLayout,代码是在网上找的。

    package com.test;  
      
    import java.util.List;  
      
    import android.content.Context;  
    import android.graphics.Rect;  
    import android.util.AttributeSet;  
    import android.view.FocusFinder;  
    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.animation.AnimationUtils;  
    import android.widget.FrameLayout;  
    import android.widget.Scroller;  
      
    /**   
     * Reference to ScrollView and HorizontalScrollView   
     */      
    public class Myscroll 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 Scroller mScroller;  
       
        /**   
         * 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;      
        private float mLastMotionX;      
       
        /**   
         * 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 boolean mFlingEnabled = true;      
       
        public Myscroll(Context context) {      
            this(context, null);      
        }      
       
        public Myscroll(Context context, AttributeSet attrs) {      
            super(context, attrs);      
            initScrollView();      
        }      
       
        @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 getLeftFadingEdgeStrength() {      
            if (getChildCount() == 0) {      
                return 0.0f;      
            }      
       
            final int length = getHorizontalFadingEdgeLength();      
            if (getScrollX() < length) {      
                return getScrollX() / (float) length;      
            }      
       
            return 1.0f;      
        }      
       
        @Override      
        protected float getRightFadingEdgeStrength() {      
            if (getChildCount() == 0) {      
                return 0.0f;      
            }      
       
            final int length = getHorizontalFadingEdgeLength();      
            final int rightEdge = getWidth() - getPaddingRight();      
            final int span = getChildAt(0).getRight() - getScrollX() - rightEdge;      
            if (span < length) {      
                return span / (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 getMaxScrollAmountV() {      
            return (int) (MAX_SCROLL_FACTOR * (getBottom() - getTop()));      
        }      
       
        public int getMaxScrollAmountH() {      
            return (int) (MAX_SCROLL_FACTOR * (getRight() - getLeft()));      
        }      
       
       
        private void initScrollView() {      
            mScroller = new Scroller(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(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 canScrollV() {      
            View child = getChildAt(0);      
            if (child != null) {      
                int childHeight = child.getHeight();      
                return getHeight() < childHeight + getPaddingTop() + getPaddingBottom();      
            }      
            return false;      
        }      
       
        private boolean canScrollH() {      
            View child = getChildAt(0);      
            if (child != null) {      
                int childWidth = child.getWidth();      
                return getWidth() < childWidth + getPaddingLeft() + getPaddingRight() ;      
            }      
            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);      
            final int widthMode = MeasureSpec.getMode(widthMeasureSpec);      
            if (heightMode == MeasureSpec.UNSPECIFIED && widthMode == MeasureSpec.UNSPECIFIED) {      
                return;      
            }      
       
            if (getChildCount() > 0) {      
                final View child = getChildAt(0);      
                int height = getMeasuredHeight();      
                int width = getMeasuredWidth();      
                if (child.getMeasuredHeight() < height || child.getMeasuredWidth() < width) {      
                    width -= getPaddingLeft();      
                    width -= getPaddingRight();      
                    int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY);      
       
                    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();      
       
            boolean handled = false;      
       
            if (event.getAction() == KeyEvent.ACTION_DOWN) {      
                switch (event.getKeyCode()) {      
                case KeyEvent.KEYCODE_DPAD_LEFT:      
                    if(canScrollH()){      
                        if (!event.isAltPressed()) {      
                            handled = arrowScrollH(View.FOCUS_LEFT);      
                        } else {      
                            handled = fullScrollH(View.FOCUS_LEFT);      
                        }      
                    }      
                    break;      
                case KeyEvent.KEYCODE_DPAD_RIGHT:      
                    if(canScrollH()){      
                        if (!event.isAltPressed()) {      
                            handled = arrowScrollH(View.FOCUS_RIGHT);      
                        } else {      
                            handled = fullScrollH(View.FOCUS_RIGHT);      
                        }      
                    }      
                    break;      
                case KeyEvent.KEYCODE_DPAD_UP:      
                    if(canScrollV()){      
                        if (!event.isAltPressed()) {      
                            handled = arrowScrollV(View.FOCUS_UP);      
                        } else {      
                            handled = fullScrollV(View.FOCUS_UP);      
                        }      
                    }      
                    break;      
                case KeyEvent.KEYCODE_DPAD_DOWN:      
                    if(canScrollV()){      
                        if (!event.isAltPressed()) {      
                            handled = arrowScrollV(View.FOCUS_DOWN);      
                        } else {      
                            handled = fullScrollV(View.FOCUS_DOWN);      
                        }      
                    }      
                    break;      
                }      
            }      
            return handled;      
        }      
       
        private boolean inChild(int x, int y) {      
            if (getChildCount() > 0) {      
                final int scrollX = getScrollX();      
                final int scrollY = getScrollY();      
                final View child = getChildAt(0);      
                return !(y < child.getTop() - scrollY      
                        || y >= child.getBottom() - scrollY      
                        || x < child.getLeft() - scrollX      
                        || x >= child.getRight() - scrollX);      
            }      
            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;      
                }      
                final float x = ev.getX(pointerIndex);      
                final int xDiff = (int) Math.abs(x - mLastMotionX);      
                if (xDiff > mTouchSlop) {      
                    mIsBeingDragged = true;      
                    mLastMotionX = x;      
                }      
                break;      
            }      
       
            case MotionEvent.ACTION_DOWN: {      
                final float x = ev.getX();      
                final float y = ev.getY();      
                if (!inChild((int)x, (int) y)) {      
                    mIsBeingDragged = false;      
                    break;      
                }      
       
                /*   
                 * Remember location of down touch.   
                 * ACTION_DOWN always refers to pointer index 0.   
                 */      
                mLastMotionY = y;      
                mLastMotionX = x;      
                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 x = ev.getX();      
                final float y = ev.getY();      
                if (!(mIsBeingDragged = inChild((int) x, (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;      
                mLastMotionX = x;      
                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;      
       
                    final float x = ev.getX(activePointerIndex);      
                    final int deltaX = (int) (mLastMotionX - x);      
                    mLastMotionX = x;      
       
                    scrollBy(deltaX, deltaY);      
                }      
                break;      
            case MotionEvent.ACTION_UP:       
                if (mIsBeingDragged) {      
                    if(mFlingEnabled){      
                        final VelocityTracker velocityTracker = mVelocityTracker;      
                        velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);      
                        int initialVelocitx = (int) velocityTracker.getXVelocity();      
                        int initialVelocity = (int) velocityTracker.getYVelocity();     
    //                  int initialVelocitx = (int) velocityTracker.getXVelocity(mActivePointerId);      
    //                  int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId);      
       
                        if (getChildCount() > 0) {      
                            if(Math.abs(initialVelocitx) > initialVelocitx || Math.abs(initialVelocity) > mMinimumVelocity) {      
                                fling(-initialVelocitx, -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;      
        }      
       
        private void onSecondaryPointerUp(MotionEvent ev) {      
            final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_ID_MASK) >>      
            MotionEvent.ACTION_POINTER_ID_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.      
                final int newPointerIndex = pointerIndex == 0 ? 1 : 0;      
                mLastMotionX = ev.getX(newPointerIndex);      
                mLastMotionY = ev.getY(newPointerIndex);      
                mActivePointerId = ev.getPointerId(newPointerIndex);      
                if (mVelocityTracker != null) {      
                    mVelocityTracker.clear();      
                }      
            }      
        }     
        /**   
         * <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 findFocusableViewInBoundsV(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;      
        }      
       
        private View findFocusableViewInBoundsH(boolean leftFocus, int left, int right) {      
       
            List<View> focusables = getFocusables(View.FOCUS_FORWARD);      
            View focusCandidate = null;      
       
            /*   
             * A fully contained focusable is one where its left is below the bound's   
             * left, and its right is above the bound's right. 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 viewLeft = view.getLeft();      
                int viewRight = view.getRight();      
       
                if (left < viewRight && viewLeft < right) {      
                    /*   
                     * the focusable is in the target area, it is a candidate for   
                     * focusing   
                     */      
       
                    final boolean viewIsFullyContained = (left < viewLeft) &&      
                    (viewRight < right);      
       
                    if (focusCandidate == null) {      
                        /* No candidate, take this one */      
                        focusCandidate = view;      
                        foundFullyContainedFocusable = viewIsFullyContained;      
                    } else {      
                        final boolean viewIsCloserToBoundary =      
                            (leftFocus && viewLeft < focusCandidate.getLeft()) ||      
                            (!leftFocus && viewRight > focusCandidate.getRight());      
       
                        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 "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 fullScrollV(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 scrollAndFocusV(direction, mTempRect.top, mTempRect.bottom);      
        }      
       
        public boolean fullScrollH(int direction) {      
            boolean right = direction == View.FOCUS_RIGHT;      
            int width = getWidth();      
       
            mTempRect.left = 0;      
            mTempRect.right = width;      
       
            if (right) {      
                int count = getChildCount();      
                if (count > 0) {      
                    View view = getChildAt(0);      
                    mTempRect.right = view.getRight();      
                    mTempRect.left = mTempRect.right - width;      
                }      
            }      
       
            return scrollAndFocusH(direction, mTempRect.left, mTempRect.right);      
        }      
       
        /**   
         * <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 scrollAndFocusV(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 = findFocusableViewInBoundsV(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;      
        }      
       
        private boolean scrollAndFocusH(int direction, int left, int right) {      
            boolean handled = true;      
       
            int width = getWidth();      
            int containerLeft = getScrollX();      
            int containerRight = containerLeft + width;      
            boolean goLeft = direction == View.FOCUS_LEFT;      
       
            View newFocused = findFocusableViewInBoundsH(goLeft, left, right);      
            if (newFocused == null) {      
                newFocused = this;      
            }      
       
            if (left >= containerLeft && right <= containerRight) {      
                handled = false;      
            } else {      
                int delta = goLeft ? (left - containerLeft) : (right - containerRight);      
                doScrollX(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 arrowScrollV(int direction) {      
       
            View currentFocused = findFocus();      
            if (currentFocused == this) currentFocused = null;      
       
            View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction);      
       
            final int maxJump = getMaxScrollAmountV();      
       
            if (nextFocused != null && isWithinDeltaOfScreenV(nextFocused, maxJump, getHeight())) {      
                nextFocused.getDrawingRect(mTempRect);      
                offsetDescendantRectToMyCoords(nextFocused, mTempRect);      
                int scrollDelta = computeScrollDeltaToGetChildRectOnScreenV(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()      
                    && isOffScreenV(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;      
        }      
       
        public boolean arrowScrollH(int direction) {      
       
            View currentFocused = findFocus();      
            if (currentFocused == this) currentFocused = null;      
       
            View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction);      
       
            final int maxJump = getMaxScrollAmountH();      
       
            if (nextFocused != null && isWithinDeltaOfScreenH(nextFocused, maxJump)) {      
                nextFocused.getDrawingRect(mTempRect);      
                offsetDescendantRectToMyCoords(nextFocused, mTempRect);      
                int scrollDelta = computeScrollDeltaToGetChildRectOnScreenH(mTempRect);      
                doScrollX(scrollDelta);      
                nextFocused.requestFocus(direction);      
            } else {      
                // no new focus      
                int scrollDelta = maxJump;      
       
                if (direction == View.FOCUS_LEFT && getScrollX() < scrollDelta) {      
                    scrollDelta = getScrollX();      
                } else if (direction == View.FOCUS_RIGHT && getChildCount() > 0) {      
       
                    int daRight = getChildAt(0).getRight();      
       
                    int screenRight = getScrollX() + getWidth();      
       
                    if (daRight - screenRight < maxJump) {      
                        scrollDelta = daRight - screenRight;      
                    }      
                }      
                if (scrollDelta == 0) {      
                    return false;      
                }      
                doScrollX(direction == View.FOCUS_RIGHT ? scrollDelta : -scrollDelta);      
            }      
       
            if (currentFocused != null && currentFocused.isFocused()      
                    && isOffScreenH(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 isOffScreenV(View descendant) {      
            return !isWithinDeltaOfScreenV(descendant, 0, getHeight());      
        }      
       
        private boolean isOffScreenH(View descendant) {      
            return !isWithinDeltaOfScreenH(descendant, 0);      
        }      
       
        /**   
         * @return whether the descendant of this scroll view is within delta   
         *  pixels of being on the screen.   
         */      
        private boolean isWithinDeltaOfScreenV(View descendant, int delta, int height) {      
            descendant.getDrawingRect(mTempRect);      
            offsetDescendantRectToMyCoords(descendant, mTempRect);      
       
            return (mTempRect.bottom + delta) >= getScrollY()      
            && (mTempRect.top - delta) <= (getScrollY() + height);      
        }      
       
        private boolean isWithinDeltaOfScreenH(View descendant, int delta) {      
            descendant.getDrawingRect(mTempRect);      
            offsetDescendantRectToMyCoords(descendant, mTempRect);      
       
            return (mTempRect.right + delta) >= getScrollX()      
            && (mTempRect.left - delta) <= (getScrollX() + getWidth());      
        }      
       
        /**   
         * 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);      
                }      
            }      
        }      
       
        private void doScrollX(int delta) {      
            if (delta != 0) {      
                if (mSmoothScrollingEnabled) {      
                    smoothScrollBy(delta, 0);      
                } else {      
                    scrollBy(delta, 0);      
                }      
            }      
        }      
       
        /**   
         * 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 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;      
       
                final int width = getWidth() - getPaddingRight() - getPaddingLeft();      
                final int right = getChildAt(0).getWidth();      
                final int maxX = Math.max(0, right - width);      
                final int scrollX = getScrollX();      
                dx = Math.max(0, Math.min(scrollX + dx, maxX)) - scrollX;      
       
                mScroller.startScroll(scrollX, scrollY, dx, dy);      
                invalidate();      
            } else {      
                if (!mScroller.isFinished()) {      
                    mScroller.abortAnimation();      
                }      
                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 - 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 computeHorizontalScrollRange() {      
            final int count = getChildCount();      
            final int contentWidth = getWidth() - getPaddingLeft() - getPaddingRight();      
            if (count == 0) {      
                return contentWidth;      
            }      
       
            return getChildAt(0).getRight();      
        }      
       
        @Override      
        protected int computeVerticalScrollOffset() {      
            return Math.max(0, super.computeVerticalScrollOffset());      
        }      
       
        @Override      
        protected int computeHorizontalScrollOffset() {      
            return Math.max(0, super.computeHorizontalScrollOffset());      
        }      
       
        @Override      
        protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) {      
            int childWidthMeasureSpec;      
            int childHeightMeasureSpec;      
       
            childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);      
       
            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 = MeasureSpec.makeMeasureSpec(      
                    lp.leftMargin + lp.rightMargin, MeasureSpec.UNSPECIFIED);      
            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 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());      
                    super.scrollTo(x, y);      
                }      
                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 scrollDeltaV = computeScrollDeltaToGetChildRectOnScreenV(mTempRect);      
            int scrollDeltaH = computeScrollDeltaToGetChildRectOnScreenH(mTempRect);      
       
            if (scrollDeltaH != 0 || scrollDeltaV != 0) {      
                scrollBy(scrollDeltaH, scrollDeltaV);      
            }      
        }      
       
        /**   
         * 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 deltaV = computeScrollDeltaToGetChildRectOnScreenV(rect);      
            final int deltaH = computeScrollDeltaToGetChildRectOnScreenH(rect);      
            final boolean scroll = deltaH != 0 || deltaV != 0;      
            if (scroll) {      
                if (immediate) {      
                    scrollBy(deltaH, deltaV);      
                } else {      
                    smoothScrollBy(deltaH, deltaV);      
                }      
            }      
            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 computeScrollDeltaToGetChildRectOnScreenV(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;      
        }      
       
        protected int computeScrollDeltaToGetChildRectOnScreenH(Rect rect) {      
            if (getChildCount() == 0) return 0;      
       
            int width = getWidth();      
            int screenLeft = getScrollX();      
            int screenRight = screenLeft + width;      
       
            int fadingEdge = getHorizontalFadingEdgeLength();      
       
            // leave room for left fading edge as long as rect isn't at very left      
            if (rect.left > 0) {      
                screenLeft += fadingEdge;      
            }      
       
            // leave room for right fading edge as long as rect isn't at very right      
            if (rect.right < getChildAt(0).getWidth()) {      
                screenRight -= fadingEdge;      
            }      
       
            int scrollXDelta = 0;      
       
            if (rect.right > screenRight && rect.left > screenLeft) {      
                // need to move right to get it in view: move right just enough so      
                // that the entire rectangle is in view (or at least the first      
                // screen size chunk).      
       
                if (rect.width() > width) {      
                    // just enough to get screen size chunk on      
                    scrollXDelta += (rect.left - screenLeft);      
                } else {      
                    // get entire rect at right of screen      
                    scrollXDelta += (rect.right - screenRight);      
                }      
       
                // make sure we aren't scrolling beyond the end of our content      
                int right = getChildAt(0).getRight();      
                int distanceToRight = right - screenRight;      
                scrollXDelta = Math.min(scrollXDelta, distanceToRight);      
       
            } else if (rect.left < screenLeft && rect.right < screenRight) {      
                // need to move right to get it in view: move right just enough so that      
                // entire rectangle is in view (or at least the first screen      
                // size chunk of it).      
       
                if (rect.width() > width) {      
                    // screen size chunk      
                    scrollXDelta -= (screenRight - rect.right);      
                } else {      
                    // entire rect at left      
                    scrollXDelta -= (screenLeft - rect.left);      
                }      
       
                // make sure we aren't scrolling any further than the left our content      
                scrollXDelta = Math.max(scrollXDelta, -getScrollX());      
            }      
            return scrollXDelta;      
        }      
       
        @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).      
            // TODO:       
            //        if (direction == View.FOCUS_FORWARD) {      
            //            direction = View.FOCUS_RIGHT;      
            //        } else if (direction == View.FOCUS_BACKWARD) {      
            //            direction = View.FOCUS_LEFT;      
            //        }      
       
            final View nextFocus = previouslyFocusedRect == null ?      
                    FocusFinder.getInstance().findNextFocus(this, null, direction) :      
                        FocusFinder.getInstance().findNextFocusFromRect(this,      
                                previouslyFocusedRect, direction);      
       
                    if (nextFocus == null) {      
                        return false;      
                    }      
       
                    //        if (isOffScreenH(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 (isWithinDeltaOfScreenV(currentFocused, 0, oldh)) {      
                currentFocused.getDrawingRect(mTempRect);      
                offsetDescendantRectToMyCoords(currentFocused, mTempRect);      
                int scrollDelta = computeScrollDeltaToGetChildRectOnScreenV(mTempRect);      
                doScrollY(scrollDelta);      
            }      
       
            final int maxJump = getRight() - getLeft();      
            if (isWithinDeltaOfScreenH(currentFocused, maxJump)) {      
                currentFocused.getDrawingRect(mTempRect);      
                offsetDescendantRectToMyCoords(currentFocused, mTempRect);      
                int scrollDelta = computeScrollDeltaToGetChildRectOnScreenH(mTempRect);      
                doScrollX(scrollDelta);      
            }      
        }          
       
        /**   
         * 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 velocityX, int velocityY) {      
            if (getChildCount() > 0) {      
                int width = getWidth() - getPaddingRight() - getPaddingLeft();      
                int right = getChildAt(0).getWidth();      
       
                int height = getHeight() - getPaddingBottom() - getPaddingTop();      
                int bottom = getChildAt(0).getHeight();      
       
                mScroller.fling(getScrollX(), getScrollY(), velocityX, velocityY,       
                        0, Math.max(0, right - width),       
                        0, Math.max(0, bottom - height));      
       
                //            final boolean movingDown = velocityX > 0 || velocityY > 0;      
                //          
                //            View newFocused =      
                //                    findFocusableViewInMyBoundsV(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) {      
            // 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 --------|   
                 *     |-- mScrollX --|   
                 */      
                return 0;      
            }      
            if ((my+n) > child) {      
                /* this case:   
                 *                    |------ me ------|   
                 *     |------ child ------|   
                 *     |-- mScrollX --|   
                 */      
                return child-my;      
            }      
            return n;      
        }      
       
        public boolean isFlingEnabled() {      
            return mFlingEnabled;      
        }      
       
        public void setFlingEnabled(boolean flingEnabled) {      
            this.mFlingEnabled = flingEnabled;      
        }      
    }  
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  • 原文地址:https://www.cnblogs.com/zhujiabin/p/6872233.html
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