// Generally, all responders which do custom touch handling should override all four of these methods. // Your responder will receive either touchesEnded:withEvent: or touchesCancelled:withEvent: for each // touch it is handling (those touches it received in touchesBegan:withEvent:). // *** You must handle cancelled touches to ensure correct behavior in your application. Failure to // do so is very likely to lead to incorrect behavior or crashes. - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event;//touch开始 - (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event;//touch移动 - (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event;//touch结束 - (void)touchesCancelled:(nullable NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event;//取消touch事件
- (nullable UIView *)hitTest:(CGPoint)point withEvent:(nullable UIEvent *)event; // recursively calls -pointInside:withEvent:. point is in the receiver's coordinate system - (BOOL)pointInside:(CGPoint)point withEvent:(nullable UIEvent *)event; // default returns YES if point is in bounds
hitTest:withEvent: 方法为给定的CGPoint 和 UIEvent返回hit test 视图。hitTest:withEvent:方法通过在自身调用pointInside:withEvent: 方法开始。 如果传递到方法hitTest:withEvent:内的点在视图的范围内，pointInside:withEvent:返回YES。同时将该响应者加入响应者栈，然后通过递归地给每个子视图调用hitTest:withEvent:方法，如果该防返回YES，则加入响应者栈。如下图（需要注意ViewController，AppDelegate,UIApplication并没有上面View的相关方法，但是由于其是UIResponder的相关类）：
