android 拖动浏览大图片例子(类似地图拖动效果)

【实例截图】

【核心代码】

/*
 * 文件名：HvScrollView.java
 * 描述：scrollView上下左右同时滑动
 * 修改人：王鹏
 * 修改时间：上午0::
 * @since 
 */
package com.example.testpathscroll;

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 HvScrollView 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 HvScrollView(Context context)
    {
        this(context, null);
    }

    public HvScrollView(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(000,
                                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: FUCK
        // 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;
    }
}