/* 
 * @ProjectName VideoGo
 * @Copyright null
 * 
 * @FileName HVScrollView.java
 * @Description 这里对文件进行描述
 * 
 * @author chenxingyf1
 * @data 2014-8-12
 * 
 * @note 这里写本文件的详细功能描述和注释
 * @note 历史记录
 * 
 * @warning 这里写本文件的相关警告
 */
package com.videogo.widget;

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;  

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;  

    private boolean mScrollViewMovedFocus;

    private float mLastMotionY;
    private float mLastMotionX;  

 
    private boolean mIsLayoutDirty = true;  
    private View mChildToScrollTo = null;  

    private boolean mIsBeingDragged = false;

    private VelocityTracker mVelocityTracker;

    private boolean mFillViewport;

    private boolean mSmoothScrollingEnabled = true;

    private int mTouchSlop;  
    private int mMinimumVelocity;  
    private int mMaximumVelocity;  

    private int mActivePointerId = INVALID_POINTER;

    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;  
    }  

    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);  
    }  

    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;  
    }  

    public boolean isFillViewport() {
        return mFillViewport;  
    }  

    public void setFillViewport(boolean fillViewport) {
        if (fillViewport != mFillViewport) {  
            mFillViewport = fillViewport;  
            requestLayout();  
        }  
    }  

    public boolean isSmoothScrollingEnabled() {
        return mSmoothScrollingEnabled;  
    }  

    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 name first
        return super.dispatchKeyEvent(event) || executeKeyEvent(event);  
    }  

    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();  
            }  
        }  
    } 
    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;  
    }  

    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);  
    }  

    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;  
    }  

    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;  
    }
    private boolean isOffScreenV(View descendant) {
        return !isWithinDeltaOfScreenV(descendant, 0, getHeight());  
    }  

    private boolean isOffScreenH(View descendant) {  
        return !isWithinDeltaOfScreenH(descendant, 0);  
    }  

    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());  
    }  

    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);  
            }  
        }  
    }  

    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();  
    }  

    public final void smoothScrollTo(int x, int y) {
        smoothScrollBy(x - getScrollX(), y - getScrollY());  
    }  

    @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();  
        }  
    }  

    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);  
        }  
    }  

    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;  
    }
    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);  
    }  


    @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);  
        }  
    }      

    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);  
    }      

    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();  
        }  
    }  

    @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;  
    }  
} 