+The {@link TextView} class also + * takes care of its own scrolling, so does not require a TwoDScrollView, but + * using the two together is possible to achieve the effect of a text view + * within a larger container. + */ +public class TwoDScrollView 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 TwoDScrollView + * knows that it does not have to do anything. + */ + private boolean mTwoDScrollViewMovedFocus; + + /** + * 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 TwoDScrollView 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; + + /** + * Whether arrow scrolling is animated. + */ + private int mTouchSlop; + private int mMinimumVelocity; + private int mMaximumVelocity; + + public TwoDScrollView(Context context) { + super(context); + initTwoDScrollView(); + } + + public TwoDScrollView(Context context, AttributeSet attrs) { + super(context, attrs); + initTwoDScrollView(); + } + + public TwoDScrollView(Context context, AttributeSet attrs, int defStyle) { + super(context, attrs, defStyle); + initTwoDScrollView(); + } + + @Override + protected float getTopFadingEdgeStrength() { + if (getChildCount() == 0) { + return 0.0f; + } + final int length = getVerticalFadingEdgeLength(); + if (getScrollY() < length) { + return getScrollY() / (float) length; + } + return 1.0f; + } + + @Override + protected float getBottomFadingEdgeStrength() { + if (getChildCount() == 0) { + return 0.0f; + } + final int length = getVerticalFadingEdgeLength(); + final int bottomEdge = getHeight() - getPaddingBottom(); + final int span = getChildAt(0).getBottom() - getScrollY() - bottomEdge; + if (span < length) { + return span / (float) length; + } + return 1.0f; + } + + @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; + } + + /** + * @return The maximum amount this scroll view will scroll in response to + * an arrow event. + */ + public int getMaxScrollAmountVertical() { + return (int) (MAX_SCROLL_FACTOR * getHeight()); + } + + public int getMaxScrollAmountHorizontal() { + return (int) (MAX_SCROLL_FACTOR * getWidth()); + } + + private void initTwoDScrollView() { + 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("TwoDScrollView can host only one direct child"); + } + super.addView(child); + } + + @Override + public void addView(View child, int index) { + if (getChildCount() > 0) { + throw new IllegalStateException("TwoDScrollView 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("TwoDScrollView 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("TwoDScrollView can host only one direct child"); + } + super.addView(child, index, params); + } + + /** + * @return Returns true this TwoDScrollView can be scrolled + */ + private boolean canScroll() { + View child = getChildAt(0); + if (child != null) { + int childHeight = child.getHeight(); + int childWidth = child.getWidth(); + return (getHeight() < childHeight + getPaddingTop() + getPaddingBottom()) || + (getWidth() < childWidth + getPaddingLeft() + getPaddingRight()); + } + return false; + } + + @Override + public boolean dispatchKeyEvent(KeyEvent event) { + // Let the focused view and/or our descendants get the key first + boolean handled = super.dispatchKeyEvent(event); + if (handled) { + return true; + } + return executeKeyEvent(event); + } + + /** + * You can call this function yourself to have the scroll view perform + * scrolling from a key event, just as if the event had been dispatched to + * it by the view hierarchy. + * + * @param event The key event to execute. + * @return Return true if the event was handled, else false. + */ + public boolean executeKeyEvent(KeyEvent event) { + mTempRect.setEmpty(); + if (!canScroll()) { + if (isFocused()) { + View currentFocused = findFocus(); + if (currentFocused == this) currentFocused = null; + View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, View.FOCUS_DOWN); + return nextFocused != null && nextFocused != this && nextFocused.requestFocus(View.FOCUS_DOWN); + } + return false; + } + boolean handled = false; + if (event.getAction() == KeyEvent.ACTION_DOWN) { + switch (event.getKeyCode()) { + case KeyEvent.KEYCODE_DPAD_UP: + if (!event.isAltPressed()) { + handled = arrowScroll(View.FOCUS_UP, false); + } else { + handled = fullScroll(View.FOCUS_UP, false); + } + break; + case KeyEvent.KEYCODE_DPAD_DOWN: + if (!event.isAltPressed()) { + handled = arrowScroll(View.FOCUS_DOWN, false); + } else { + handled = fullScroll(View.FOCUS_DOWN, false); + } + break; + case KeyEvent.KEYCODE_DPAD_LEFT: + if (!event.isAltPressed()) { + handled = arrowScroll(View.FOCUS_LEFT, true); + } else { + handled = fullScroll(View.FOCUS_LEFT, true); + } + break; + case KeyEvent.KEYCODE_DPAD_RIGHT: + if (!event.isAltPressed()) { + handled = arrowScroll(View.FOCUS_RIGHT, true); + } else { + handled = fullScroll(View.FOCUS_RIGHT, true); + } + break; + } + } + return handled; + } + + @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; + } + if (!canScroll()) { + mIsBeingDragged = false; + return false; + } + final float y = ev.getY(); + final float x = ev.getX(); + switch (action) { + 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 yDiff = (int) Math.abs(y - mLastMotionY); + final int xDiff = (int) Math.abs(x - mLastMotionX); + if (yDiff > mTouchSlop || xDiff > mTouchSlop) { + mIsBeingDragged = true; + } + break; + + case MotionEvent.ACTION_DOWN: + /* Remember location of down touch */ + mLastMotionY = y; + mLastMotionX = x; + + /* + * 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; + 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 (!canScroll()) { + return false; + } + + if (mVelocityTracker == null) { + mVelocityTracker = VelocityTracker.obtain(); + } + mVelocityTracker.addMovement(ev); + + final int action = ev.getAction(); + final float y = ev.getY(); + final float x = ev.getX(); + + switch (action) { + case MotionEvent.ACTION_DOWN: + /* + * 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; + break; + case MotionEvent.ACTION_MOVE: + // Scroll to follow the motion event + int deltaX = (int) (mLastMotionX - x); + int deltaY = (int) (mLastMotionY - y); + mLastMotionX = x; + mLastMotionY = y; + + if (deltaX < 0) { + if (getScrollX() < 0) { + deltaX = 0; + } + } else if (deltaX > 0) { + final int rightEdge = getWidth() - getPaddingRight(); + final int availableToScroll = getChildAt(0).getRight() - getScrollX() - rightEdge; + if (availableToScroll > 0) { + deltaX = Math.min(availableToScroll, deltaX); + } else { + deltaX = 0; + } + } + if (deltaY < 0) { + if (getScrollY() < 0) { + deltaY = 0; + } + } else if (deltaY > 0) { + final int bottomEdge = getHeight() - getPaddingBottom(); + final int availableToScroll = getChildAt(0).getBottom() - getScrollY() - bottomEdge; + if (availableToScroll > 0) { + deltaY = Math.min(availableToScroll, deltaY); + } else { + deltaY = 0; + } + } + if (deltaY != 0 || deltaX != 0) + scrollBy(deltaX, deltaY); + break; + case MotionEvent.ACTION_UP: + final VelocityTracker velocityTracker = mVelocityTracker; + velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); + int initialXVelocity = (int) velocityTracker.getXVelocity(); + int initialYVelocity = (int) velocityTracker.getYVelocity(); + if ((Math.abs(initialXVelocity) + Math.abs(initialYVelocity) > mMinimumVelocity) && getChildCount() > 0) { + fling(-initialXVelocity, -initialYVelocity); + } + if (mVelocityTracker != null) { + mVelocityTracker.recycle(); + mVelocityTracker = null; + } + } + return true; + } + + /** + * Finds the next focusable component that fits in this View's bounds + * (excluding fading edges) pretending that this View's top is located at + * the parameter top. + * + * @param topFocus look for a candidate is the one at the top of the bounds + * if topFocus is true, or at the bottom of the bounds if topFocus is + * false + * @param top the top offset of the bounds in which a focusable must be + * found (the fading edge is assumed to start at this position) + * @param preferredFocusable the View that has highest priority and will be + * returned if it is within my bounds (null is valid) + * @return the next focusable component in the bounds or null if none can be + * found + */ + private View findFocusableViewInMyBounds(final boolean topFocus, final int top, final boolean leftFocus, final int left, View preferredFocusable) { + /* + * The fading edge's transparent side should be considered for focus + * since it's mostly visible, so we divide the actual fading edge length + * by 2. + */ + final int verticalFadingEdgeLength = getVerticalFadingEdgeLength() / 2; + final int topWithoutFadingEdge = top + verticalFadingEdgeLength; + final int bottomWithoutFadingEdge = top + getHeight() - verticalFadingEdgeLength; + final int horizontalFadingEdgeLength = getHorizontalFadingEdgeLength() / 2; + final int leftWithoutFadingEdge = left + horizontalFadingEdgeLength; + final int rightWithoutFadingEdge = left + getWidth() - horizontalFadingEdgeLength; + + if ((preferredFocusable != null) + && (preferredFocusable.getTop() < bottomWithoutFadingEdge) + && (preferredFocusable.getBottom() > topWithoutFadingEdge) + && (preferredFocusable.getLeft() < rightWithoutFadingEdge) + && (preferredFocusable.getRight() > leftWithoutFadingEdge)) { + return preferredFocusable; + } + return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, bottomWithoutFadingEdge, leftFocus, leftWithoutFadingEdge, rightWithoutFadingEdge); + } + + /** + * Finds the next focusable component that fits in the specified bounds. + *
+ * + * @param topFocus look for a candidate is the one at the top of the bounds + * if topFocus is true, or at the bottom of the bounds if topFocus is + * false + * @param top the top offset of the bounds in which a focusable must be + * found + * @param bottom the bottom offset of the bounds in which a focusable must + * be found + * @return the next focusable component in the bounds or null if none can + * be found + */ + private View findFocusableViewInBounds(boolean topFocus, int top, int bottom, boolean leftFocus, int left, int right) { + ListHandles 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.
+ * + * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} + * to go the top of the view or + * {@link android.view.View#FOCUS_DOWN} to go the bottom + * @return true if the key event is consumed by this method, false otherwise + */ + public boolean fullScroll(int direction, boolean horizontal) { + if (!horizontal) { + boolean down = direction == View.FOCUS_DOWN; + int height = getHeight(); + mTempRect.top = 0; + mTempRect.bottom = height; + if (down) { + int count = getChildCount(); + if (count > 0) { + View view = getChildAt(count - 1); + mTempRect.bottom = view.getBottom(); + mTempRect.top = mTempRect.bottom - height; + } + } + return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom, 0, 0, 0); + } else { + boolean right = direction == View.FOCUS_DOWN; + int width = getWidth(); + mTempRect.left = 0; + mTempRect.right = width; + if (right) { + int count = getChildCount(); + if (count > 0) { + View view = getChildAt(count - 1); + mTempRect.right = view.getBottom(); + mTempRect.left = mTempRect.right - width; + } + } + return scrollAndFocus(0, 0, 0, direction, mTempRect.top, mTempRect.bottom); + } + } + + /** + *Scrolls the view to make the area defined by top and
+ * bottom 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.
The scroll range of a scroll view is the overall height of all of its + * children.
+ */ + @Override + protected int computeVerticalScrollRange() { + int count = getChildCount(); + return count == 0 ? getHeight() : (getChildAt(0)).getBottom(); + } + + @Override + protected int computeHorizontalScrollRange() { + int count = getChildCount(); + return count == 0 ? getWidth() : (getChildAt(0)).getRight(); + } + + @Override + protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { + ViewGroup.LayoutParams lp = child.getLayoutParams(); + int childWidthMeasureSpec; + int childHeightMeasureSpec; + + childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, getPaddingLeft() + getPaddingRight(), lp.width); + childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); + + child.measure(childWidthMeasureSpec, childHeightMeasureSpec); + } + + @Override + protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed) { + final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); + final int childWidthMeasureSpec = 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 oldX = getScrollX(); + int oldY = getScrollY(); + int x = mScroller.getCurrX(); + int y = mScroller.getCurrY(); + if (getChildCount() > 0) { + View child = getChildAt(0); + scrollTo(clamp(x, getWidth() - getPaddingRight() - getPaddingLeft(), child.getWidth()), + clamp(y, getHeight() - getPaddingBottom() - getPaddingTop(), child.getHeight())); + } else { + scrollTo(x, y); + } + if (oldX != getScrollX() || oldY != getScrollY()) { + onScrollChanged(getScrollX(), getScrollY(), oldX, oldY); + } + + // 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 TwoDScrollView coordinates */ + offsetDescendantRectToMyCoords(child, mTempRect); + int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); + if (scrollDelta != 0) { + scrollBy(0, scrollDelta); + } + } + + /** + * If rect is off screen, scroll just enough to get it (or at least the + * first screen size chunk of it) on screen. + * + * @param rect The rectangle. + * @param immediate True to scroll immediately without animation + * @return true if scrolling was performed + */ + private boolean scrollToChildRect(Rect rect, boolean immediate) { + final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); + final boolean scroll = delta != 0; + if (scroll) { + if (immediate) { + scrollBy(0, delta); + } else { + smoothScrollBy(0, delta); + } + } + return scroll; + } + + /** + * Compute the amount to scroll in the Y direction in order to get + * a rectangle completely on the screen (or, if taller than the screen, + * at least the first screen size chunk of it). + * + * @param rect The rect. + * @return The scroll delta. + */ + protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { + if (getChildCount() == 0) return 0; + int height = getHeight(); + int screenTop = getScrollY(); + int screenBottom = screenTop + height; + int fadingEdge = getVerticalFadingEdgeLength(); + // leave room for top fading edge as long as rect isn't at very top + if (rect.top > 0) { + screenTop += fadingEdge; + } + + // leave room for bottom fading edge as long as rect isn't at very bottom + if (rect.bottom < getChildAt(0).getHeight()) { + screenBottom -= fadingEdge; + } + int scrollYDelta = 0; + if (rect.bottom > screenBottom && rect.top > screenTop) { + // need to move down to get it in view: move down just enough so + // that the entire rectangle is in view (or at least the first + // screen size chunk). + if (rect.height() > height) { + // just enough to get screen size chunk on + scrollYDelta += (rect.top - screenTop); + } else { + // get entire rect at bottom of screen + scrollYDelta += (rect.bottom - screenBottom); + } + + // make sure we aren't scrolling beyond the end of our content + int bottom = getChildAt(0).getBottom(); + int distanceToBottom = bottom - screenBottom; + scrollYDelta = Math.min(scrollYDelta, distanceToBottom); + + } else if (rect.top < screenTop && rect.bottom < screenBottom) { + // need to move up to get it in view: move up just enough so that + // entire rectangle is in view (or at least the first screen + // size chunk of it). + + if (rect.height() > height) { + // screen size chunk + scrollYDelta -= (screenBottom - rect.bottom); + } else { + // entire rect at top + scrollYDelta -= (screenTop - rect.top); + } + + // make sure we aren't scrolling any further than the top our content + scrollYDelta = Math.max(scrollYDelta, -getScrollY()); + } + return scrollYDelta; + } + + @Override + public void requestChildFocus(View child, View focused) { + if (!mTwoDScrollViewMovedFocus) { + if (!mIsLayoutDirty) { + scrollToChild(focused); + } else { + // The child may not be laid out yet, we can't compute the scroll yet + mChildToScrollTo = focused; + } + } + super.requestChildFocus(child, focused); + } + + /** + * When looking for focus in children of a scroll view, need to be a little + * more careful not to give focus to something that is scrolled off screen. + * + * This is more expensive than the default {@link android.view.ViewGroup} + * implementation, otherwise this behavior might have been made the default. + */ + @Override + protected boolean onRequestFocusInDescendants(int direction, Rect previouslyFocusedRect) { + // convert from forward / backward notation to up / down / left / right + // (ugh). + if (direction == View.FOCUS_FORWARD) { + direction = View.FOCUS_DOWN; + } else if (direction == View.FOCUS_BACKWARD) { + direction = View.FOCUS_UP; + } + + final View nextFocus = previouslyFocusedRect == null ? + FocusFinder.getInstance().findNextFocus(this, null, direction) : + FocusFinder.getInstance().findNextFocusFromRect(this, + previouslyFocusedRect, direction); + + if (nextFocus == null) { + return false; + } + + 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. + currentFocused.getDrawingRect(mTempRect); + offsetDescendantRectToMyCoords(currentFocused, mTempRect); + int scrollDeltaX = computeScrollDeltaToGetChildRectOnScreen(mTempRect); + int scrollDeltaY = computeScrollDeltaToGetChildRectOnScreen(mTempRect); + doScroll(scrollDeltaX, scrollDeltaY); + } + + /** + * 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/curor 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 height = getHeight() - getPaddingBottom() - getPaddingTop(); + int bottom = getChildAt(0).getHeight(); + int width = getWidth() - getPaddingRight() - getPaddingLeft(); + int right = getChildAt(0).getWidth(); + + mScroller.fling(getScrollX(), getScrollY(), velocityX, velocityY, 0, right - width, 0, bottom - height); + + final boolean movingDown = velocityY > 0; + final boolean movingRight = velocityX > 0; + + View newFocused = findFocusableViewInMyBounds(movingRight, mScroller.getFinalX(), movingDown, mScroller.getFinalY(), findFocus()); + if (newFocused == null) { + newFocused = this; + } + + if (newFocused != findFocus() && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { + mTwoDScrollViewMovedFocus = true; + mTwoDScrollViewMovedFocus = false; + } + + awakenScrollBars(mScroller.getDuration()); + invalidate(); + } + } + + /** + * {@inheritDoc} + * + *This version also clamps the scrolling to the bounds of our child. + */ + 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; + } +}