TwoDScrollViewWithBar

/*
 * Copyright (C) 2006 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * Revised 5/19/2010 by GORGES
 * Now supports two-dimensional view scrolling
 * http://GORGES.us
 */

package us.gorges.viewaclue;

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.LinearLayout;
import android.widget.Scroller;
import android.widget.TextView;

/**
 * Layout container for a view hierarchy that can be scrolled by the user,
 * allowing it to be larger than the physical display.  A TwoDScrollView
 * is a {@link FrameLayout}, meaning you should place one child in it
 * containing the entire contents to scroll; this child may itself be a layout
 * manager with a complex hierarchy of objects.  A child that is often used
 * is a {@link LinearLayout} in a vertical orientation, presenting a vertical
 * array of top-level items that the user can scroll through.
 *
 * <p>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 TwoDScrollViewWithBar 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 TwoDScrollViewWithBar(Context context) {
   super(context);
   initTwoDScrollView();
 }

 public TwoDScrollViewWithBar(Context context, AttributeSet attrs) {
   super(context, attrs);
   initTwoDScrollView();
 }

 public TwoDScrollViewWithBar(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_UP, true);
         } else {
           handled = fullScroll(View.FOCUS_UP, true);
         }
         break;
       case KeyEvent.KEYCODE_DPAD_RIGHT:
         if (!event.isAltPressed()) {
           handled = arrowScroll(View.FOCUS_DOWN, true);
         } else {
           handled = fullScroll(View.FOCUS_DOWN, 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.
 * </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 findFocusableViewInBounds(boolean topFocus, int top, int bottom, boolean leftFocus, int left, int right) {
   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();
     int viewLeft = view.getLeft();
     int viewRight = view.getRight();

     if (top < viewBottom && viewTop < bottom && left < viewRight && viewLeft < right) {
       /*
       * the focusable is in the target area, it is a candidate for
       * focusing
       */
       final boolean viewIsFullyContained = (top < viewTop) && (viewBottom < bottom) && (left < viewLeft) && (viewRight < right);
       if (focusCandidate == null) {
         /* No candidate, take this one */
         focusCandidate = view;
         foundFullyContainedFocusable = viewIsFullyContained;
       } else {
         final boolean viewIsCloserToVerticalBoundary =
           (topFocus && viewTop < focusCandidate.getTop()) ||
           (!topFocus && viewBottom > focusCandidate.getBottom());
         final boolean viewIsCloserToHorizontalBoundary =
           (leftFocus && viewLeft < focusCandidate.getLeft()) ||
           (!leftFocus && viewRight > focusCandidate.getRight());
         if (foundFullyContainedFocusable) {
           if (viewIsFullyContained && viewIsCloserToVerticalBoundary && viewIsCloserToHorizontalBoundary) {
             /*
              * 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 (viewIsCloserToVerticalBoundary && viewIsCloserToHorizontalBoundary) {
             /*
              * 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 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);
   }
 }

 /**
  * <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 scrollAndFocus(int directionY, int top, int bottom, int directionX, int left, int right) {
   boolean handled = true;
   int height = getHeight();
   int containerTop = getScrollY();
   int containerBottom = containerTop + height;
   boolean up = directionY == View.FOCUS_UP;
   int width = getWidth();
   int containerLeft = getScrollX();
   int containerRight = containerLeft + width;
   boolean leftwards = directionX == View.FOCUS_UP;
   View newFocused = findFocusableViewInBounds(up, top, bottom, leftwards, left, right);
   if (newFocused == null) {
     newFocused = this;
   }
   if ((top >= containerTop && bottom <= containerBottom) || (left >= containerLeft && right <= containerRight)) {
     handled = false;
   } else {
     int deltaY = up ? (top - containerTop) : (bottom - containerBottom);
     int deltaX = leftwards ? (left - containerLeft) : (right - containerRight);
     doScroll(deltaX, deltaY);
   }
   if (newFocused != findFocus() && newFocused.requestFocus(directionY)) {
     mTwoDScrollViewMovedFocus = true;
     mTwoDScrollViewMovedFocus = 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 arrowScroll(int direction, boolean horizontal) {
   View currentFocused = findFocus();
   if (currentFocused == this) currentFocused = null;
   View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction);
   final int maxJump = horizontal ? getMaxScrollAmountHorizontal() : getMaxScrollAmountVertical();

   if (!horizontal) {
     if (nextFocused != null) {
       nextFocused.getDrawingRect(mTempRect);
       offsetDescendantRectToMyCoords(nextFocused, mTempRect);
       int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect);
       doScroll(0, 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;
       }
       doScroll(0, direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta);
     }
   } else {
     if (nextFocused != null) {
       nextFocused.getDrawingRect(mTempRect);
       offsetDescendantRectToMyCoords(nextFocused, mTempRect);
       int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect);
       doScroll(scrollDelta, 0);
       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;
       }
       doScroll(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta, 0);
     }
   }
   return true;
 }

 /**
  * Smooth scroll by a Y delta
  *
  * @param delta the number of pixels to scroll by on the Y axis
  */
 private void doScroll(int deltaX, int deltaY) {
   if (deltaX != 0 || deltaY != 0) {
     smoothScrollBy(deltaX, deltaY);
   }
 }

 /**
  * 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 final void smoothScrollBy(int dx, int dy) {
   long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll;
   if (duration > ANIMATED_SCROLL_GAP) {
     mScroller.startScroll(getScrollX(), getScrollY(), dx, dy);
     awakenScrollBars(mScroller.getDuration());
     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() {
   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 = getChildMeasureSpec(parentWidthMeasureSpec,
   getPaddingLeft() + getPaddingRight() + lp.leftMargin + lp.rightMargin + widthUsed, lp.width);
   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}
  *
  * <p>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;
 }
}