@Override
        public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {
            onPanelDragged(top);
            invalidate();
        }
Tests scrollability within child views of v given a delta of dx.

@param v      View to test for horizontal scrollability
@param checkV Whether the view v passed should itself be checked for scrollability (true),
              or just its children (false).
@param dx     Delta scrolled in pixels
@param x      X coordinate of the active touch point
@param y      Y coordinate of the active touch point
@return true if child views of v can be scrolled by delta of dx.
app/src/main/java/home/smart/fly/animations/widget/slidepanel/SlidingUpPanelLayout.java