title: why the "shouldReceiveTouch" returns "NO", the "PanGesture" still works?
body: <p>Such as title, I have a superView A and a childView B. The A has a panGestureRecognizer. When I swipe the B, it will trigger the panGestureRecognizer of A. So I return No in the shouldReceiveTouch of A, But the panGestureRecognizer still works whick makes me confused.</p>