Android中实现上下左右都可滑动的ScrollView

import java.util.List;

import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.FocusFinder;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.view.animation.AnimationUtils;
import android.widget.FrameLayout;
import android.widget.Scroller;

/**

• Reference to ScrollView and HorizontalScrollView
  */
  public class HVScrollView extends FrameLayout {
  static final int ANIMATED_SCROLL_GAP = 250;

  static final float MAX_SCROLL_FACTOR = 0.5f;

  private long mLastScroll;

  private final Rect mTempRect = new Rect();
  private Scroller mScroller;

  /**

  • Flag to indicate that we are moving focus ourselves. This is so the
  • code that watches for focus changes initiated outside this ScrollView
  • knows that it does not have to do anything.
    */
    private boolean mScrollViewMovedFocus;

  /**

  • Position of the last motion event.
    */
    private float mLastMotionY;
    private float mLastMotionX;

  /**

  • True when the layout has changed but the traversal has not come through yet.
  • Ideally the view hierarchy would keep track of this for us.
    */
    private boolean mIsLayoutDirty = true;

  /**

  • The child to give focus to in the event that a child has requested focus while the
  • layout is dirty. This prevents the scroll from being wrong if the child has not been
  • laid out before requesting focus.
    */
    private View mChildToScrollTo = null;

  /**

  • True if the user is currently dragging this ScrollView around. This is
  • not the same as 'is being flinged', which can be checked by
  • mScroller.isFinished() (flinging begins when the user lifts his finger).
    */
    private boolean mIsBeingDragged = false;

  /**

  • Determines speed during touch scrolling
    */
    private VelocityTracker mVelocityTracker;

  /**

  • When set to true, the scroll view measure its child to make it fill the currently
  • visible area.
    */
    private boolean mFillViewport;

  /**

  • Whether arrow scrolling is animated.
    */
    private boolean mSmoothScrollingEnabled = true;

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

  /**

  • ID of the active pointer. This is used to retain consistency during
  • drags/flings if multiple pointers are used.
    */
    private int mActivePointerId = INVALID_POINTER;

  /**

  • Sentinel value for no current active pointer.
  • Used by {@link #mActivePointerId}.
    */
    private static final int INVALID_POINTER = -1;

  private boolean mFlingEnabled = true;

  public HVScrollView(Context context) {
  this(context, null);
  }

  public HVScrollView(Context context, AttributeSet attrs) {
  super(context, attrs);
  initScrollView();
  }

  @Override
  protected float getTopFadingEdgeStrength() {
  if (getChildCount() == 0) {
  return 0.0f;
  }

  final int length = getVerticalFadingEdgeLength();     
  if (getScrollY() < length) {     
      return getScrollY() / (float) length;     
  }     
  
  return 1.0f;     

  }

  @Override
  protected float getLeftFadingEdgeStrength() {
  if (getChildCount() == 0) {
  return 0.0f;
  }

  final int length = getHorizontalFadingEdgeLength();     
  if (getScrollX() < length) {     
      return getScrollX() / (float) length;     
  }     
  
  return 1.0f;     

  }

  @Override
  protected float getRightFadingEdgeStrength() {
  if (getChildCount() == 0) {
  return 0.0f;
  }

  final int length = getHorizontalFadingEdgeLength();     
  final int rightEdge = getWidth() - getPaddingRight();     
  final int span = getChildAt(0).getRight() - getScrollX() - rightEdge;     
  if (span < length) {     
      return span / (float) length;     
  }     
  
  return 1.0f;     

  }

  @Override
  protected float getBottomFadingEdgeStrength() {
  if (getChildCount() == 0) {
  return 0.0f;
  }

  final int length = getVerticalFadingEdgeLength();     
  final int bottomEdge = getHeight() - getPaddingBottom();     
  final int span = getChildAt(0).getBottom() - getScrollY() - bottomEdge;     
  if (span < length) {     
      return span / (float) length;     
  }     
  
  return 1.0f;     

  }

  /**

  • @return The maximum amount this scroll view will scroll in response to
  • an arrow event.
    /
    public int getMaxScrollAmountV() {
    return (int) (MAX_SCROLL_FACTOR (getBottom() - getTop()));
    }

  public int getMaxScrollAmountH() {
  return (int) (MAX_SCROLL_FACTOR * (getRight() - getLeft()));
  }

  private void initScrollView() {
  mScroller = new Scroller(getContext());
  setFocusable(true);
  setDescendantFocusability(FOCUS_AFTER_DESCENDANTS);
  setWillNotDraw(false);
  final ViewConfiguration configuration = ViewConfiguration.get(getContext());
  mTouchSlop = configuration.getScaledTouchSlop();
  mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();
  mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
  }

  @Override
  public void addView(View child) {
  if (getChildCount() > 0) {
  throw new IllegalStateException("ScrollView can host only one direct child");
  }

  super.addView(child);     

  }

  @Override
  public void addView(View child, int index) {
  if (getChildCount() > 0) {
  throw new IllegalStateException("ScrollView can host only one direct child");
  }

  super.addView(child, index);     

  }

  @Override
  public void addView(View child, ViewGroup.LayoutParams params) {
  if (getChildCount() > 0) {
  throw new IllegalStateException("ScrollView can host only one direct child");
  }

  super.addView(child, params);     

  }

  @Override
  public void addView(View child, int index, ViewGroup.LayoutParams params) {
  if (getChildCount() > 0) {
  throw new IllegalStateException("ScrollView can host only one direct child");
  }

  super.addView(child, index, params);     

  }

  /**

  • @return Returns true this ScrollView can be scrolled
    */
    private boolean canScrollV() {
    View child = getChildAt(0);
    if (child != null) {
    int childHeight = child.getHeight();
    return getHeight() < childHeight + getPaddingTop() + getPaddingBottom();
    }
    return false;
    }

  private boolean canScrollH() {
  View child = getChildAt(0);
  if (child != null) {
  int childWidth = child.getWidth();
  return getWidth() < childWidth + getPaddingLeft() + getPaddingRight() ;
  }
  return false;
  }

  /**

  • Indicates whether this ScrollView's content is stretched to fill the viewport.
  • @return True if the content fills the viewport, false otherwise.
    */
    public boolean isFillViewport() {
    return mFillViewport;
    }

  /**

  • Indicates this ScrollView whether it should stretch its content height to fill
  • the viewport or not.
  • @param fillViewport True to stretch the content's height to the viewport's
  • boundaries, false otherwise.
    */
    public void setFillViewport(boolean fillViewport) {
    if (fillViewport != mFillViewport) {
    mFillViewport = fillViewport;
    requestLayout();
    }
    }

  /**

  • @return Whether arrow scrolling will animate its transition.
    */
    public boolean isSmoothScrollingEnabled() {
    return mSmoothScrollingEnabled;
    }

  /**

  • Set whether arrow scrolling will animate its transition.
  • @param smoothScrollingEnabled whether arrow scrolling will animate its transition
    */
    public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) {
    mSmoothScrollingEnabled = smoothScrollingEnabled;
    }

  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  super.onMeasure(widthMeasureSpec, heightMeasureSpec);

  if (!mFillViewport) {     
      return;     
  }     
  
  final int heightMode = MeasureSpec.getMode(heightMeasureSpec);     
  final int widthMode = MeasureSpec.getMode(widthMeasureSpec);     
  if (heightMode == MeasureSpec.UNSPECIFIED && widthMode == MeasureSpec.UNSPECIFIED) {     
      return;     
  }     
  
  if (getChildCount() > 0) {     
      final View child = getChildAt(0);     
      int height = getMeasuredHeight();     
      int width = getMeasuredWidth();     
      if (child.getMeasuredHeight() < height || child.getMeasuredWidth() < width) {     
          width -= getPaddingLeft();     
          width -= getPaddingRight();     
          int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY);     
  
          height -= getPaddingTop();     
          height -= getPaddingBottom();     
          int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);     
  
          child.measure(childWidthMeasureSpec, childHeightMeasureSpec);     
      }     
  }     

  }
  @Override
  public boolean dispatchKeyEvent(KeyEvent event) {
  // Let the focused view and/or our descendants get the key first
  return super.dispatchKeyEvent(event) || executeKeyEvent(event);
  }

  /**

  • You can call this function yourself to have the scroll view perform
  • scrolling from a key event, just as if the event had been dispatched to
  • it by the view hierarchy.
  • @param event The key event to execute.

  • @return Return true if the event was handled, else false.
    */
    public boolean executeKeyEvent(KeyEvent event) {
    mTempRect.setEmpty();

    boolean handled = false;

    if (event.getAction() == KeyEvent.ACTION_DOWN) {
    switch (event.getKeyCode()) {
    case KeyEvent.KEYCODE_DPAD_LEFT:
    if(canScrollH()){
    if (!event.isAltPressed()) {
    handled = arrowScrollH(View.FOCUS_LEFT);
    } else {
    handled = fullScrollH(View.FOCUS_LEFT);
    }
    }
    break;
    case KeyEvent.KEYCODE_DPAD_RIGHT:
    if(canScrollH()){
    if (!event.isAltPressed()) {
    handled = arrowScrollH(View.FOCUS_RIGHT);
    } else {
    handled = fullScrollH(View.FOCUS_RIGHT);
    }
    }
    break;
    case KeyEvent.KEYCODE_DPAD_UP:
    if(canScrollV()){
    if (!event.isAltPressed()) {
    handled = arrowScrollV(View.FOCUS_UP);
    } else {
    handled = fullScrollV(View.FOCUS_UP);
    }
    }
    break;
    case KeyEvent.KEYCODE_DPAD_DOWN:
    if(canScrollV()){
    if (!event.isAltPressed()) {
    handled = arrowScrollV(View.FOCUS_DOWN);
    } else {
    handled = fullScrollV(View.FOCUS_DOWN);
    }
    }
    break;
    }
    }
    return handled;
    }

  private boolean inChild(int x, int y) {
  if (getChildCount() > 0) {
  final int scrollX = getScrollX();
  final int scrollY = getScrollY();
  final View child = getChildAt(0);
  return !(y < child.getTop() - scrollY
  || y >= child.getBottom() - scrollY
  || x < child.getLeft() - scrollX
  || x >= child.getRight() - scrollX);
  }
  return false;
  }

  @Override
  public boolean onInterceptTouchEvent(MotionEvent ev) {
  /*

  • This method JUST determines whether we want to intercept the motion.
  • If we return true, onMotionEvent will be called and we do the actual

  • scrolling there.
    */

    /*

  • Shortcut the most recurring case: the user is in the dragging
  • state and he is moving his finger. We want to intercept this

  • motion.
    */
    final int action = ev.getAction();
    if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) {
    return true;
    }

    switch (action & MotionEvent.ACTION_MASK) {
    case MotionEvent.ACTION_MOVE: {
    /*

    • mIsBeingDragged == false, otherwise the shortcut would have caught it. Check

    • whether the user has moved far enough from his original down touch.
      */

      /*

    • Locally do absolute value. mLastMotionY is set to the y value

    • of the down event.
      */
      final int activePointerId = mActivePointerId;
      if (activePointerId == INVALID_POINTER) {
      // If we don't have a valid id, the touch down wasn't on content.
      break;
      }

      final int pointerIndex = ev.findPointerIndex(activePointerId);
      final float y = ev.getY(pointerIndex);
      final int yDiff = (int) Math.abs(y - mLastMotionY);
      if (yDiff > mTouchSlop) {
      mIsBeingDragged = true;
      mLastMotionY = y;
      }
      final float x = ev.getX(pointerIndex);
      final int xDiff = (int) Math.abs(x - mLastMotionX);
      if (xDiff > mTouchSlop) {
      mIsBeingDragged = true;
      mLastMotionX = x;
      }
      break;
      }

    case MotionEvent.ACTION_DOWN: {
    final float x = ev.getX();
    final float y = ev.getY();
    if (!inChild((int)x, (int) y)) {
    mIsBeingDragged = false;
    break;
    }

    /* 
     * Remember location of down touch. 
     * ACTION_DOWN always refers to pointer index 0. 
     */     
    mLastMotionY = y;     
    mLastMotionX = x;     
    mActivePointerId = ev.getPointerId(0);     
    
    /* 
     * If being flinged and user touches the screen, initiate drag; 
     * otherwise don't.  mScroller.isFinished should be false when 
     * being flinged. 
     */     
    mIsBeingDragged = !mScroller.isFinished();     
    break;     

    }

    case MotionEvent.ACTION_CANCEL:
    case MotionEvent.ACTION_UP:
    / Release the drag /
    mIsBeingDragged = false;
    mActivePointerId = INVALID_POINTER;
    break;
    case MotionEvent.ACTION_POINTER_UP:
    onSecondaryPointerUp(ev);
    break;
    }

    /*

  • The only time we want to intercept motion events is if we are in the
  • drag mode.
    */
    return mIsBeingDragged;
    }

  @Override
  public boolean onTouchEvent(MotionEvent ev) {

  if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) {     
      // Don't handle edge touches immediately -- they may actually belong to one of our     
      // descendants.     
      return false;     
  }     
  
  if (mVelocityTracker == null) {     
      mVelocityTracker = VelocityTracker.obtain();     
  }     
  mVelocityTracker.addMovement(ev);     
  
  final int action = ev.getAction();     
  
  switch (action & MotionEvent.ACTION_MASK) {     
  case MotionEvent.ACTION_DOWN: {     
      final float x = ev.getX();     
      final float y = ev.getY();     
      if (!(mIsBeingDragged = inChild((int) x, (int) y))) {     
          return false;     
      }     
  
      /* 
       * If being flinged and user touches, stop the fling. isFinished 
       * will be false if being flinged. 
       */     
      if (!mScroller.isFinished()) {     
          mScroller.abortAnimation();     
      }     
  
      // Remember where the motion event started     
      mLastMotionY = y;     
      mLastMotionX = x;     
      mActivePointerId = ev.getPointerId(0);     
      break;     
  }     
  case MotionEvent.ACTION_MOVE:     
      if (mIsBeingDragged) {     
          // Scroll to follow the motion event     
          final int activePointerIndex = ev.findPointerIndex(mActivePointerId);     
          final float y = ev.getY(activePointerIndex);     
          final int deltaY = (int) (mLastMotionY - y);     
          mLastMotionY = y;     
  
          final float x = ev.getX(activePointerIndex);     
          final int deltaX = (int) (mLastMotionX - x);     
          mLastMotionX = x;     
  
          scrollBy(deltaX, deltaY);     
      }     
      break;     
  case MotionEvent.ACTION_UP:      
      if (mIsBeingDragged) {     
          if(mFlingEnabled){     
              final VelocityTracker velocityTracker = mVelocityTracker;     
              velocityTracker.computeCurrentVelocity(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;
  }
  }