讓超出父視圖的子視圖響應事件

• (UIView )hitTest:(CGPoint)point withEvent:(UIEvent )event {
  UIView *view = [super hitTest:point withEvent:event];
  if (view == nil) {
  for (UIView *subView in self.subviews) {
  CGPoint tp = [subView convertPoint:point fromView:self];
  if (CGRectContainsPoint(subView.bounds, tp)) {
  view = subView;
  }
  }
  }
  return view;
  }