HVScrollView 垂直和水平均可滚动

HVScrollView.java 2.1以上测试可用

/** 
 * 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(1000, mMaximumVelocity);  
					int initialVelocitx = (int) velocityTracker.getXVelocity();  
					int initialVelocity = (int) velocityTracker.getYVelocity(); 
//					int initialVelocitx = (int) velocityTracker.getXVelocity(mActivePointerId);  
//					int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId);  

					if (getChildCount() > 0) {  
						if(Math.abs(initialVelocitx) > initialVelocitx || Math.abs(initialVelocity) > mMinimumVelocity) {  
							fling(-initialVelocitx, -initialVelocity);  
						}  

					}  
				}  

				mActivePointerId = INVALID_POINTER;  
				mIsBeingDragged = false;  

				if (mVelocityTracker != null) {  
					mVelocityTracker.recycle();  
					mVelocityTracker = null;  
				}  
			}  
			break;  
		case MotionEvent.ACTION_CANCEL:  
			if (mIsBeingDragged && getChildCount() > 0) {  
				mActivePointerId = INVALID_POINTER;  
				mIsBeingDragged = false;  
				if (mVelocityTracker != null) {  
					mVelocityTracker.recycle();  
					mVelocityTracker = null;  
				}  
			}  
			break;  
		case MotionEvent.ACTION_POINTER_UP:  
			onSecondaryPointerUp(ev);  
			break;  
		}  
		return true;  
	}  

	private void onSecondaryPointerUp(MotionEvent ev) {  
		final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_ID_MASK) >>  
		MotionEvent.ACTION_POINTER_ID_SHIFT;  
		final int pointerId = ev.getPointerId(pointerIndex);  
		if (pointerId == mActivePointerId) {  
			// This was our active pointer going up. Choose a new  
			// active pointer and adjust accordingly.  
			final int newPointerIndex = pointerIndex == 0 ? 1 : 0;  
			mLastMotionX = ev.getX(newPointerIndex);  
			mLastMotionY = ev.getY(newPointerIndex);  
			mActivePointerId = ev.getPointerId(newPointerIndex);  
			if (mVelocityTracker != null) {  
				mVelocityTracker.clear();  
			}  
		}  
	} 
	/** 
	 * <p> 
	 * Finds the next focusable component that fits in the specified bounds. 
	 * </p> 
	 * 
	 * @param topFocus look for a candidate is the one at the top of the bounds 
	 *                 if topFocus is true, or at the bottom of the bounds if topFocus is 
	 *                 false 
	 * @param top      the top offset of the bounds in which a focusable must be 
	 *                 found 
	 * @param bottom   the bottom offset of the bounds in which a focusable must 
	 *                 be found 
	 * @return the next focusable component in the bounds or null if none can 
	 *         be found 
	 */  
	private View findFocusableViewInBoundsV(boolean topFocus, int top, int bottom) {  

		List<View> focusables = getFocusables(View.FOCUS_FORWARD);  
		View focusCandidate = null;  

		/* 
		 * A fully contained focusable is one where its top is below the bound's 
		 * top, and its bottom is above the bound's bottom. A partially 
		 * contained focusable is one where some part of it is within the 
		 * bounds, but it also has some part that is not within bounds.  A fully contained 
		 * focusable is preferred to a partially contained focusable. 
		 */  
		boolean foundFullyContainedFocusable = false;  

		int count = focusables.size();  
		for (int i = 0; i < count; i++) {  
			View view = focusables.get(i);  
			int viewTop = view.getTop();  
			int viewBottom = view.getBottom();  

			if (top < viewBottom && viewTop < bottom) {  
				/* 
				 * the focusable is in the target area, it is a candidate for 
				 * focusing 
				 */  

				final boolean viewIsFullyContained = (top < viewTop) &&  
				(viewBottom < bottom);  

				if (focusCandidate == null) {  
					/* No candidate, take this one */  
					focusCandidate = view;  
					foundFullyContainedFocusable = viewIsFullyContained;  
				} else {  
					final boolean viewIsCloserToBoundary =  
						(topFocus && viewTop < focusCandidate.getTop()) ||  
						(!topFocus && viewBottom > focusCandidate  
								.getBottom());  

					if (foundFullyContainedFocusable) {  
						if (viewIsFullyContained && viewIsCloserToBoundary) {  
							/* 
							 * We're dealing with only fully contained views, so 
							 * it has to be closer to the boundary to beat our 
							 * candidate 
							 */  
							focusCandidate = view;  
						}  
					} else {  
						if (viewIsFullyContained) {  
							/* Any fully contained view beats a partially contained view */  
							focusCandidate = view;  
							foundFullyContainedFocusable = true;  
						} else if (viewIsCloserToBoundary) {  
							/* 
							 * Partially contained view beats another partially 
							 * contained view if it's closer 
							 */  
							focusCandidate = view;  
						}  
					}  
				}  
			}  
		}  

		return focusCandidate;  
	}  

	private View findFocusableViewInBoundsH(boolean leftFocus, int left, int right) {  

		List<View> focusables = getFocusables(View.FOCUS_FORWARD);  
		View focusCandidate = null;  

		/* 
		 * A fully contained focusable is one where its left is below the bound's 
		 * left, and its right is above the bound's right. A partially 
		 * contained focusable is one where some part of it is within the 
		 * bounds, but it also has some part that is not within bounds.  A fully contained 
		 * focusable is preferred to a partially contained focusable. 
		 */  
		boolean foundFullyContainedFocusable = false;  

		int count = focusables.size();  
		for (int i = 0; i < count; i++) {  
			View view = focusables.get(i);  
			int viewLeft = view.getLeft();  
			int viewRight = view.getRight();  

			if (left < viewRight && viewLeft < right) {  
				/* 
				 * the focusable is in the target area, it is a candidate for 
				 * focusing 
				 */  

				final boolean viewIsFullyContained = (left < viewLeft) &&  
				(viewRight < right);  

				if (focusCandidate == null) {  
					/* No candidate, take this one */  
					focusCandidate = view;  
					foundFullyContainedFocusable = viewIsFullyContained;  
				} else {  
					final boolean viewIsCloserToBoundary =  
						(leftFocus && viewLeft < focusCandidate.getLeft()) ||  
						(!leftFocus && viewRight > focusCandidate.getRight());  

					if (foundFullyContainedFocusable) {  
						if (viewIsFullyContained && viewIsCloserToBoundary) {  
							/* 
							 * We're dealing with only fully contained views, so 
							 * it has to be closer to the boundary to beat our 
							 * candidate 
							 */  
							focusCandidate = view;  
						}  
					} else {  
						if (viewIsFullyContained) {  
							/* Any fully contained view beats a partially contained view */  
							focusCandidate = view;  
							foundFullyContainedFocusable = true;  
						} else if (viewIsCloserToBoundary) {  
							/* 
							 * Partially contained view beats another partially 
							 * contained view if it's closer 
							 */  
							focusCandidate = view;  
						}  
					}  
				}  
			}  
		}  

		return focusCandidate;  
	}  

	/** 
	 * <p>Handles scrolling in response to a "home/end" shortcut press. This 
	 * method will scroll the view to the top or bottom and give the focus 
	 * to the topmost/bottommost component in the new visible area. If no 
	 * component is a good candidate for focus, this scrollview reclaims the 
	 * focus.</p> 
	 * 
	 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 
	 *                  to go the top of the view or 
	 *                  {@link android.view.View#FOCUS_DOWN} to go the bottom 
	 * @return true if the key event is consumed by this method, false otherwise 
	 */  
	public boolean fullScrollV(int direction) {  
		boolean down = direction == View.FOCUS_DOWN;  
		int height = getHeight();  

		mTempRect.top = 0;  
		mTempRect.bottom = height;  

		if (down) {  
			int count = getChildCount();  
			if (count > 0) {  
				View view = getChildAt(count - 1);  
				mTempRect.bottom = view.getBottom();  
				mTempRect.top = mTempRect.bottom - height;  
			}  
		}  

		return scrollAndFocusV(direction, mTempRect.top, mTempRect.bottom);  
	}  

	public boolean fullScrollH(int direction) {  
		boolean right = direction == View.FOCUS_RIGHT;  
		int width = getWidth();  

		mTempRect.left = 0;  
		mTempRect.right = width;  

		if (right) {  
			int count = getChildCount();  
			if (count > 0) {  
				View view = getChildAt(0);  
				mTempRect.right = view.getRight();  
				mTempRect.left = mTempRect.right - width;  
			}  
		}  

		return scrollAndFocusH(direction, mTempRect.left, mTempRect.right);  
	}  

	/** 
	 * <p>Scrolls the view to make the area defined by <code>top</code> and 
	 * <code>bottom</code> visible. This method attempts to give the focus 
	 * to a component visible in this area. If no component can be focused in 
	 * the new visible area, the focus is reclaimed by this scrollview.</p> 
	 * 
	 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 
	 *                  to go upward 
	 *                  {@link android.view.View#FOCUS_DOWN} to downward 
	 * @param top       the top offset of the new area to be made visible 
	 * @param bottom    the bottom offset of the new area to be made visible 
	 * @return true if the key event is consumed by this method, false otherwise 
	 */  
	private boolean scrollAndFocusV(int direction, int top, int bottom) {  
		boolean handled = true;  

		int height = getHeight();  
		int containerTop = getScrollY();  
		int containerBottom = containerTop + height;  
		boolean up = direction == View.FOCUS_UP;  

		View newFocused = findFocusableViewInBoundsV(up, top, bottom);  
		if (newFocused == null) {  
			newFocused = this;  
		}  

		if (top >= containerTop && bottom <= containerBottom) {  
			handled = false;  
		} else {  
			int delta = up ? (top - containerTop) : (bottom - containerBottom);  
			doScrollY(delta);  
		}  

		if (newFocused != findFocus() && newFocused.requestFocus(direction)) {  
			mScrollViewMovedFocus = true;  
			mScrollViewMovedFocus = false;  
		}  

		return handled;  
	}  

	private boolean scrollAndFocusH(int direction, int left, int right) {  
		boolean handled = true;  

		int width = getWidth();  
		int containerLeft = getScrollX();  
		int containerRight = containerLeft + width;  
		boolean goLeft = direction == View.FOCUS_LEFT;  

		View newFocused = findFocusableViewInBoundsH(goLeft, left, right);  
		if (newFocused == null) {  
			newFocused = this;  
		}  

		if (left >= containerLeft && right <= containerRight) {  
			handled = false;  
		} else {  
			int delta = goLeft ? (left - containerLeft) : (right - containerRight);  
			doScrollX(delta);  
		}  

		if (newFocused != findFocus() && newFocused.requestFocus(direction)) {  
			mScrollViewMovedFocus = true;  
			mScrollViewMovedFocus = false;  
		}  

		return handled;  
	}  

	/** 
	 * Handle scrolling in response to an up or down arrow click. 
	 * 
	 * @param direction The direction corresponding to the arrow key that was 
	 *                  pressed 
	 * @return True if we consumed the event, false otherwise 
	 */  
	public boolean arrowScrollV(int direction) {  

		View currentFocused = findFocus();  
		if (currentFocused == this) currentFocused = null;  

		View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction);  

		final int maxJump = getMaxScrollAmountV();  

		if (nextFocused != null && isWithinDeltaOfScreenV(nextFocused, maxJump, getHeight())) {  
			nextFocused.getDrawingRect(mTempRect);  
			offsetDescendantRectToMyCoords(nextFocused, mTempRect);  
			int scrollDelta = computeScrollDeltaToGetChildRectOnScreenV(mTempRect);  
			doScrollY(scrollDelta);  
			nextFocused.requestFocus(direction);  
		} else {  
			// no new focus  
			int scrollDelta = maxJump;  

			if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) {  
				scrollDelta = getScrollY();  
			} else if (direction == View.FOCUS_DOWN) {  
				if (getChildCount() > 0) {  
					int daBottom = getChildAt(0).getBottom();  

					int screenBottom = getScrollY() + getHeight();  

					if (daBottom - screenBottom < maxJump) {  
						scrollDelta = daBottom - screenBottom;  
					}  
				}  
			}  
			if (scrollDelta == 0) {  
				return false;  
			}  
			doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta);  
		}  

		if (currentFocused != null && currentFocused.isFocused()  
				&& isOffScreenV(currentFocused)) {  
			// previously focused item still has focus and is off screen, give  
			// it up (take it back to ourselves)  
			// (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are  
			// sure to  
			// get it)  
			final int descendantFocusability = getDescendantFocusability();  // save  
			setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS);  
			requestFocus();  
			setDescendantFocusability(descendantFocusability);  // restore  
		}  
		return true;  
	}  

	public boolean arrowScrollH(int direction) {  

		View currentFocused = findFocus();  
		if (currentFocused == this) currentFocused = null;  

		View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction);  

		final int maxJump = getMaxScrollAmountH();  

		if (nextFocused != null && isWithinDeltaOfScreenH(nextFocused, maxJump)) {  
			nextFocused.getDrawingRect(mTempRect);  
			offsetDescendantRectToMyCoords(nextFocused, mTempRect);  
			int scrollDelta = computeScrollDeltaToGetChildRectOnScreenH(mTempRect);  
			doScrollX(scrollDelta);  
			nextFocused.requestFocus(direction);  
		} else {  
			// no new focus  
			int scrollDelta = maxJump;  

			if (direction == View.FOCUS_LEFT && getScrollX() < scrollDelta) {  
				scrollDelta = getScrollX();  
			} else if (direction == View.FOCUS_RIGHT && getChildCount() > 0) {  

				int daRight = getChildAt(0).getRight();  

				int screenRight = getScrollX() + getWidth();  

				if (daRight - screenRight < maxJump) {  
					scrollDelta = daRight - screenRight;  
				}  
			}  
			if (scrollDelta == 0) {  
				return false;  
			}  
			doScrollX(direction == View.FOCUS_RIGHT ? scrollDelta : -scrollDelta);  
		}  

		if (currentFocused != null && currentFocused.isFocused()  
				&& isOffScreenH(currentFocused)) {  
			// previously focused item still has focus and is off screen, give  
			// it up (take it back to ourselves)  
			// (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are  
			// sure to  
			// get it)  
			final int descendantFocusability = getDescendantFocusability();  // save  
			setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS);  
			requestFocus();  
			setDescendantFocusability(descendantFocusability);  // restore  
		}  
		return true;  
	}
	/** 
	 * @return whether the descendant of this scroll view is scrolled off 
	 *  screen. 
	 */  
	private boolean isOffScreenV(View descendant) {  
		return !isWithinDeltaOfScreenV(descendant, 0, getHeight());  
	}  

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

	/** 
	 * @return whether the descendant of this scroll view is within delta 
	 *  pixels of being on the screen. 
	 */  
	private boolean isWithinDeltaOfScreenV(View descendant, int delta, int height) {  
		descendant.getDrawingRect(mTempRect);  
		offsetDescendantRectToMyCoords(descendant, mTempRect);  

		return (mTempRect.bottom + delta) >= getScrollY()  
		&& (mTempRect.top - delta) <= (getScrollY() + height);  
	}  

	private boolean isWithinDeltaOfScreenH(View descendant, int delta) {  
		descendant.getDrawingRect(mTempRect);  
		offsetDescendantRectToMyCoords(descendant, mTempRect);  

		return (mTempRect.right + delta) >= getScrollX()  
		&& (mTempRect.left - delta) <= (getScrollX() + getWidth());  
	}  

	/** 
	 * Smooth scroll by a Y delta 
	 * 
	 * @param delta the number of pixels to scroll by on the Y axis 
	 */  
	private void doScrollY(int delta) {  
		if (delta != 0) {  
			if (mSmoothScrollingEnabled) {  
				smoothScrollBy(0, delta);  
			} else {  
				scrollBy(0, delta);  
			}  
		}  
	}  

	private void doScrollX(int delta) {  
		if (delta != 0) {  
			if (mSmoothScrollingEnabled) {  
				smoothScrollBy(delta, 0);  
			} else {  
				scrollBy(delta, 0);  
			}  
		}  
	}  

	/** 
	 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 
	 * 
	 * @param dx the number of pixels to scroll by on the X axis 
	 * @param dy the number of pixels to scroll by on the Y axis 
	 */  
	public void smoothScrollBy(int dx, int dy) {  
		if (getChildCount() == 0) {  
			// Nothing to do.  
			return;  
		}  
		long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll;  
		if (duration > ANIMATED_SCROLL_GAP) {  
			final int height = getHeight() - getPaddingBottom() - getPaddingTop();  
			final int bottom = getChildAt(0).getHeight();  
			final int maxY = Math.max(0, bottom - height);  
			final int scrollY = getScrollY();  
			dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY;  

			final int width = getWidth() - getPaddingRight() - getPaddingLeft();  
			final int right = getChildAt(0).getWidth();  
			final int maxX = Math.max(0, right - width);  
			final int scrollX = getScrollX();  
			dx = Math.max(0, Math.min(scrollX + dx, maxX)) - scrollX;  

			mScroller.startScroll(scrollX, scrollY, dx, dy);  
			invalidate();  
		} else {  
			if (!mScroller.isFinished()) {  
				mScroller.abortAnimation();  
			}  
			scrollBy(dx, dy);  
		}  
		mLastScroll = AnimationUtils.currentAnimationTimeMillis();  
	}  

	/** 
	 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 
	 * 
	 * @param x the position where to scroll on the X axis 
	 * @param y the position where to scroll on the Y axis 
	 */  
	public final void smoothScrollTo(int x, int y) {  
		smoothScrollBy(x - getScrollX(), y - getScrollY());  
	}  

	/** 
	 * <p>The scroll range of a scroll view is the overall height of all of its 
	 * children.</p> 
	 */  
	@Override  
	protected int computeVerticalScrollRange() {  
		final int count = getChildCount();  
		final int contentHeight = getHeight() - getPaddingBottom() - getPaddingTop();  
		if (count == 0) {  
			return contentHeight;  
		}  

		return getChildAt(0).getBottom();  
	}  

	@Override  
	protected int computeHorizontalScrollRange() {  
		final int count = getChildCount();  
		final int contentWidth = getWidth() - getPaddingLeft() - getPaddingRight();  
		if (count == 0) {  
			return contentWidth;  
		}  

		return getChildAt(0).getRight();  
	}  

	@Override  
	protected int computeVerticalScrollOffset() {  
		return Math.max(0, super.computeVerticalScrollOffset());  
	}  

	@Override  
	protected int computeHorizontalScrollOffset() {  
		return Math.max(0, super.computeHorizontalScrollOffset());  
	}  

	@Override  
	protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) {  
		int childWidthMeasureSpec;  
		int childHeightMeasureSpec;  

		childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);  

		childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);  

		child.measure(childWidthMeasureSpec, childHeightMeasureSpec);  
	}  

	@Override  
	protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed,  
			int parentHeightMeasureSpec, int heightUsed) {  
		final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();  

		final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(  
				lp.leftMargin + lp.rightMargin, MeasureSpec.UNSPECIFIED);  
		final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(  
				lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED);  

		child.measure(childWidthMeasureSpec, childHeightMeasureSpec);  
	}  

	@Override  
	public void computeScroll() {  
		if (mScroller.computeScrollOffset()) {  
			// This is called at drawing time by ViewGroup.  We don't want to  
			// re-show the scrollbars at this point, which scrollTo will do,  
			// so we replicate most of scrollTo here.  
			//  
			//         It's a little odd to call onScrollChanged from inside the drawing.  
			//  
			//         It is, except when you remember that computeScroll() is used to  
			//         animate scrolling. So unless we want to defer the onScrollChanged()  
			//         until the end of the animated scrolling, we don't really have a  
			//         choice here.  
			//  
			//         I agree.  The alternative, which I think would be worse, is to post  
			//         something and tell the subclasses later.  This is bad because there  
			//         will be a window where mScrollX/Y is different from what the app  
			//         thinks it is.  
			//  
			int x = mScroller.getCurrX();  
			int y = mScroller.getCurrY();  

			if (getChildCount() > 0) {  
				View child = getChildAt(0);  
				x = clamp(x, getWidth() - getPaddingRight() - getPaddingLeft(), child.getWidth());  
				y = clamp(y, getHeight() - getPaddingBottom() - getPaddingTop(), child.getHeight());  
				super.scrollTo(x, y);  
			}  
			awakenScrollBars();  

			// Keep on drawing until the animation has finished.  
			postInvalidate();  
		}  
	}  

	/** 
	 * Scrolls the view to the given child. 
	 * 
	 * @param child the View to scroll to 
	 */  
	private void scrollToChild(View child) {  
		child.getDrawingRect(mTempRect);  

		/* Offset from child's local coordinates to ScrollView coordinates */  
		offsetDescendantRectToMyCoords(child, mTempRect);  

		int scrollDeltaV = computeScrollDeltaToGetChildRectOnScreenV(mTempRect);  
		int scrollDeltaH = computeScrollDeltaToGetChildRectOnScreenH(mTempRect);  

		if (scrollDeltaH != 0 || scrollDeltaV != 0) {  
			scrollBy(scrollDeltaH, scrollDeltaV);  
		}  
	}  

	/** 
	 * If rect is off screen, scroll just enough to get it (or at least the 
	 * first screen size chunk of it) on screen. 
	 * 
	 * @param rect      The rectangle. 
	 * @param immediate True to scroll immediately without animation 
	 * @return true if scrolling was performed 
	 */  
	private boolean scrollToChildRect(Rect rect, boolean immediate) {  
		final int deltaV = computeScrollDeltaToGetChildRectOnScreenV(rect);  
		final int deltaH = computeScrollDeltaToGetChildRectOnScreenH(rect);  
		final boolean scroll = deltaH != 0 || deltaV != 0;  
		if (scroll) {  
			if (immediate) {  
				scrollBy(deltaH, deltaV);  
			} else {  
				smoothScrollBy(deltaH, deltaV);  
			}  
		}  
		return scroll;  
	}
	/** 
	 * Compute the amount to scroll in the Y direction in order to get 
	 * a rectangle completely on the screen (or, if taller than the screen, 
	 * at least the first screen size chunk of it). 
	 * 
	 * @param rect The rect. 
	 * @return The scroll delta. 
	 */  
	protected int computeScrollDeltaToGetChildRectOnScreenV(Rect rect) {  
		if (getChildCount() == 0) return 0;  

		int height = getHeight();  
		int screenTop = getScrollY();  
		int screenBottom = screenTop + height;  

		int fadingEdge = getVerticalFadingEdgeLength();  

		// leave room for top fading edge as long as rect isn't at very top  
		if (rect.top > 0) {  
			screenTop += fadingEdge;  
		}  

		// leave room for bottom fading edge as long as rect isn't at very bottom  
		if (rect.bottom < getChildAt(0).getHeight()) {  
			screenBottom -= fadingEdge;  
		}  

		int scrollYDelta = 0;  

		if (rect.bottom > screenBottom && rect.top > screenTop) {  
			// need to move down to get it in view: move down just enough so  
			// that the entire rectangle is in view (or at least the first  
			// screen size chunk).  

			if (rect.height() > height) {  
				// just enough to get screen size chunk on  
				scrollYDelta += (rect.top - screenTop);  
			} else {  
				// get entire rect at bottom of screen  
				scrollYDelta += (rect.bottom - screenBottom);  
			}  

			// make sure we aren't scrolling beyond the end of our content  
			int bottom = getChildAt(0).getBottom();  
			int distanceToBottom = bottom - screenBottom;  
			scrollYDelta = Math.min(scrollYDelta, distanceToBottom);  

		} else if (rect.top < screenTop && rect.bottom < screenBottom) {  
			// need to move up to get it in view: move up just enough so that  
			// entire rectangle is in view (or at least the first screen  
			// size chunk of it).  

			if (rect.height() > height) {  
				// screen size chunk  
				scrollYDelta -= (screenBottom - rect.bottom);  
			} else {  
				// entire rect at top  
				scrollYDelta -= (screenTop - rect.top);  
			}  

			// make sure we aren't scrolling any further than the top our content  
			scrollYDelta = Math.max(scrollYDelta, -getScrollY());  
		}  
		return scrollYDelta;  
	}  

	protected int computeScrollDeltaToGetChildRectOnScreenH(Rect rect) {  
		if (getChildCount() == 0) return 0;  

		int width = getWidth();  
		int screenLeft = getScrollX();  
		int screenRight = screenLeft + width;  

		int fadingEdge = getHorizontalFadingEdgeLength();  

		// leave room for left fading edge as long as rect isn't at very left  
		if (rect.left > 0) {  
			screenLeft += fadingEdge;  
		}  

		// leave room for right fading edge as long as rect isn't at very right  
		if (rect.right < getChildAt(0).getWidth()) {  
			screenRight -= fadingEdge;  
		}  

		int scrollXDelta = 0;  

		if (rect.right > screenRight && rect.left > screenLeft) {  
			// need to move right to get it in view: move right just enough so  
			// that the entire rectangle is in view (or at least the first  
			// screen size chunk).  

			if (rect.width() > width) {  
				// just enough to get screen size chunk on  
				scrollXDelta += (rect.left - screenLeft);  
			} else {  
				// get entire rect at right of screen  
				scrollXDelta += (rect.right - screenRight);  
			}  

			// make sure we aren't scrolling beyond the end of our content  
			int right = getChildAt(0).getRight();  
			int distanceToRight = right - screenRight;  
			scrollXDelta = Math.min(scrollXDelta, distanceToRight);  

		} else if (rect.left < screenLeft && rect.right < screenRight) {  
			// need to move right to get it in view: move right just enough so that  
			// entire rectangle is in view (or at least the first screen  
			// size chunk of it).  

			if (rect.width() > width) {  
				// screen size chunk  
				scrollXDelta -= (screenRight - rect.right);  
			} else {  
				// entire rect at left  
				scrollXDelta -= (screenLeft - rect.left);  
			}  

			// make sure we aren't scrolling any further than the left our content  
			scrollXDelta = Math.max(scrollXDelta, -getScrollX());  
		}  
		return scrollXDelta;  
	}  

	@Override  
	public void requestChildFocus(View child, View focused) {  
		if (!mScrollViewMovedFocus) {  
			if (!mIsLayoutDirty) {  
				scrollToChild(focused);  
			} else {  
				// The child may not be laid out yet, we can't compute the scroll yet  
				mChildToScrollTo = focused;  
			}  
		}  
		super.requestChildFocus(child, focused);  
	}  


	/** 
	 * When looking for focus in children of a scroll view, need to be a little 
	 * more careful not to give focus to something that is scrolled off screen. 
	 * 
	 * This is more expensive than the default {@link android.view.ViewGroup} 
	 * implementation, otherwise this behavior might have been made the default. 
	 */  
	@Override  
	protected boolean onRequestFocusInDescendants(int direction,  
			Rect previouslyFocusedRect) {  

		// convert from forward / backward notation to up / down / left / right  
		// (ugh).  
		// TODO: 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;  
	}  
}

评论

2 楼 nocb 2012-09-04  

怎么用啊？ 没看明白  ，要写layout么？

1 楼 bcysq 2012-03-22  

写的蛮好的！我今天也想这么写来着，没成功，看着的才懂了！