BookResultsHeaderViewHolder.java 文件源码

@Override
public void onExpansionToggled(boolean expanded) {
    super.onExpansionToggled(expanded);
    ObjectAnimator imageViewObjectAnimator;
    if (expanded) { // rotate clockwise
         imageViewObjectAnimator = ObjectAnimator.ofFloat(mArrowExpandImageView ,
                View.ROTATION, ROTATED_POSITION,INITIAL_POSITION);

    } else { // rotate counterclockwise
         imageViewObjectAnimator = ObjectAnimator.ofFloat(mArrowExpandImageView ,
                View.ROTATION,INITIAL_POSITION, ROTATED_POSITION);
    }

    imageViewObjectAnimator.setDuration(1000);
    imageViewObjectAnimator.setInterpolator(new OvershootInterpolator());
    imageViewObjectAnimator.start();
}