code: public void fling(int velocityY) {
  		if (getChildCount() > 0) {
  			int height = getHeight() - getPaddingBottom() - getPaddingTop();
  			int bottom = getChildAt(0).getHeight();
  
  			mScroller.fling(getScrollX(), getScrollY(), 0, velocityY, 0, 0, 0,
  					Math.max(0, bottom - height), 0, height/2);
  
  			ViewCompat.postInvalidateOnAnimation(this);
  		}
  	}
docs: 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.