android.support.v4.view.ViewCompat#postOnAnimationDelayed ( )源码实例Demo

/**
 * Starts the scroll animation.
 */
private void startAnimating() {
    if (mRunnable == null) {
        mRunnable = new ScrollAnimationRunnable();
    }

    mAnimating = true;
    mNeedsReset = true;

    if (!mAlreadyDelayed && mActivationDelay > 0) {
        ViewCompat.postOnAnimationDelayed(mTarget, mRunnable, mActivationDelay);
    } else {
        mRunnable.run();
    }

    // If we start animating again before the user lifts their finger, we
    // already know it's not a tap and don't need an activation delay.
    mAlreadyDelayed = true;
}
 

/**
 * Starts the scroll animation.
 */
private void startAnimating() {
    if (mRunnable == null) {
        mRunnable = new ScrollAnimationRunnable();
    }

    mAnimating = true;
    mNeedsReset = true;

    if (!mAlreadyDelayed && mActivationDelay > 0) {
        ViewCompat.postOnAnimationDelayed(mTarget, mRunnable, mActivationDelay);
    } else {
        mRunnable.run();
    }

    // If we start animating again before the user lifts their finger, we
    // already know it's not a tap and don't need an activation delay.
    mAlreadyDelayed = true;
}
 

/**
 * Starts the scroll animation.
 */
private void startAnimating() {
    if (mRunnable == null) {
        mRunnable = new ScrollAnimationRunnable();
    }

    mAnimating = true;
    mNeedsReset = true;

    if (!mAlreadyDelayed && mActivationDelay > 0) {
        ViewCompat.postOnAnimationDelayed(mTarget, mRunnable, mActivationDelay);
    } else {
        mRunnable.run();
    }

    // If we start animating again before the user lifts their finger, we
    // already know it's not a tap and don't need an activation delay.
    mAlreadyDelayed = true;
}
 

/**
 * Starts the scroll animation.
 */
private void startAnimating() {
    if (mRunnable == null) {
        mRunnable = new ScrollAnimationRunnable();
    }

    mAnimating = true;
    mNeedsReset = true;

    if (!mAlreadyDelayed && mActivationDelay > 0) {
        ViewCompat.postOnAnimationDelayed(mTarget, mRunnable, mActivationDelay);
    } else {
        mRunnable.run();
    }

    // If we start animating again before the user lifts their finger, we
    // already know it's not a tap and don't need an activation delay.
    mAlreadyDelayed = true;
}
 

private void startAnimating() {
    if (this.mRunnable == null) {
        this.mRunnable = new ScrollAnimationRunnable();
    }
    this.mAnimating = true;
    this.mNeedsReset = true;
    if (this.mAlreadyDelayed || this.mActivationDelay <= 0) {
        this.mRunnable.run();
    } else {
        ViewCompat.postOnAnimationDelayed(this.mTarget, this.mRunnable, (long) this.mActivationDelay);
    }
    this.mAlreadyDelayed = true;
}
 

/**
 * This handles any sort of scrolling that may occur after a touch is finished.  This may be
 * momentum scrolling (fling) or because you have pagingEnabled on the scroll view.  Because we
 * don't get any events from Android about this lifecycle, we do all our detection by creating a
 * runnable that checks if we scrolled in the last frame and if so assumes we are still scrolling.
 */
private void handlePostTouchScrolling(int velocityX, int velocityY) {
  // If we aren't going to do anything (send events or snap to page), we can early exit out.
  if (!mSendMomentumEvents && !mPagingEnabled && !isScrollPerfLoggingEnabled()) {
    return;
  }

  // Check if we are already handling this which may occur if this is called by both the touch up
  // and a fling call
  if (mPostTouchRunnable != null) {
    return;
  }

  if (mSendMomentumEvents) {
    enableFpsListener();
    ReactScrollViewHelper.emitScrollMomentumBeginEvent(this, velocityX, velocityY);
  }

  mActivelyScrolling = false;
  mPostTouchRunnable = new Runnable() {

    private boolean mSnappingToPage = false;

    @Override
    public void run() {
      if (mActivelyScrolling) {
        // We are still scrolling so we just post to check again a frame later
        mActivelyScrolling = false;
        ViewCompat.postOnAnimationDelayed(ReactScrollView.this,
          this,
          ReactScrollViewHelper.MOMENTUM_DELAY);
      } else {
        if (mPagingEnabled && !mSnappingToPage) {
          // Only if we have pagingEnabled and we have not snapped to the page do we
          // need to continue checking for the scroll.  And we cause that scroll by asking for it
          mSnappingToPage = true;
          flingAndSnap(0);
          ViewCompat.postOnAnimationDelayed(ReactScrollView.this,
            this,
            ReactScrollViewHelper.MOMENTUM_DELAY);
        } else {
          if (mSendMomentumEvents) {
            ReactScrollViewHelper.emitScrollMomentumEndEvent(ReactScrollView.this);
          }
          ReactScrollView.this.mPostTouchRunnable = null;
          disableFpsListener();
        }
      }
    }
  };
  ViewCompat.postOnAnimationDelayed(ReactScrollView.this,
    mPostTouchRunnable,
    ReactScrollViewHelper.MOMENTUM_DELAY);
}
 

/**
 * This handles any sort of scrolling that may occur after a touch is finished.  This may be
 * momentum scrolling (fling) or because you have pagingEnabled on the scroll view.  Because we
 * don't get any events from Android about this lifecycle, we do all our detection by creating a
 * runnable that checks if we scrolled in the last frame and if so assumes we are still scrolling.
 */
private void handlePostTouchScrolling(int velocityX, int velocityY) {
  // If we aren't going to do anything (send events or snap to page), we can early exit out.
  if (!mSendMomentumEvents && !mPagingEnabled && !isScrollPerfLoggingEnabled()) {
    return;
  }

  // Check if we are already handling this which may occur if this is called by both the touch up
  // and a fling call
  if (mPostTouchRunnable != null) {
    return;
  }

  if (mSendMomentumEvents) {
    ReactScrollViewHelper.emitScrollMomentumBeginEvent(this, velocityX, velocityY);
  }

  mActivelyScrolling = false;
  mPostTouchRunnable = new Runnable() {

    private boolean mSnappingToPage = false;

    @Override
    public void run() {
      if (mActivelyScrolling) {
        // We are still scrolling so we just post to check again a frame later
        mActivelyScrolling = false;
        ViewCompat.postOnAnimationDelayed(ReactHorizontalScrollView.this,
          this,
          ReactScrollViewHelper.MOMENTUM_DELAY);
      } else {
        if (mPagingEnabled && !mSnappingToPage) {
          // Only if we have pagingEnabled and we have not snapped to the page do we
          // need to continue checking for the scroll.  And we cause that scroll by asking for it
          mSnappingToPage = true;
          flingAndSnap(0);
          ViewCompat.postOnAnimationDelayed(ReactHorizontalScrollView.this,
            this,
            ReactScrollViewHelper.MOMENTUM_DELAY);
        } else {
          if (mSendMomentumEvents) {
            ReactScrollViewHelper.emitScrollMomentumEndEvent(ReactHorizontalScrollView.this);
          }
          ReactHorizontalScrollView.this.mPostTouchRunnable = null;
          disableFpsListener();
        }
      }
    }
  };
  ViewCompat.postOnAnimationDelayed(ReactHorizontalScrollView.this,
    mPostTouchRunnable,
    ReactScrollViewHelper.MOMENTUM_DELAY);
}