iOS 事件传递和视图响应链

1、事件的分类

multitouch events：所谓的多点触摸事件，即用户触摸屏幕交互产生的事件类型；
motion events：所谓的移动事件。是指用户在摇晃、移动和倾斜手机的时候产生的事件称为移动事件。这类事件依赖于iPhone手机里边的加速器，陀螺仪等传感器；
remote control events：所谓的远程控制事件。指的是用户在操作多媒体的时候产生的事件。比如，播放音乐，视频等。

2、触摸事件

UIEvent
iOS将触摸事件定义第一个手指开始触摸屏幕到最后一个手指离开屏幕为一个触摸事件。用类UIEvent表示。
UITouch
一个手指第一次点屏幕，会形成一个UITouch对象，知道离开销毁，表示触碰。UITouch对象能表明了当前手指触碰屏幕的位置，状态。状态分为开始触碰，移动和离开。
根据定义，UIEvent实际包括了多个UITouch对象。有几个手指触碰，就会有几个UITouch对象。代码定义如下:

typedef NS_ENUM(NSInteger, UITouchPhase) {

    UITouchPhaseBegan,             // whenever a finger touches the surface.

    UITouchPhaseMoved,             // whenever a finger moves on the surface.

    UITouchPhaseStationary,        // whenever a finger is touching the surface but hasn't moved since the previous event.

    UITouchPhaseEnded,             // whenever a finger leaves the surface.

    UITouchPhaseCancelled,         // whenever a touch doesn't end but we need to stop tracking (e.g. putting device to face)

};

@interface UITouch : NSObject

@property(nonatomic,readonly) NSTimeInterval      timestamp;
@property(nonatomic,readonly) UITouchPhase        phase;
@property(nonatomic,readonly) NSUInteger          tapCount;   // touch down within a certain point within a certain amount of time
@property(nonatomic,readonly) UITouchType         type API_AVAILABLE(ios(9.0));

// majorRadius and majorRadiusTolerance are in points
// The majorRadius will be accurate +/- the majorRadiusTolerance
@property(nonatomic,readonly) CGFloat majorRadius API_AVAILABLE(ios(8.0));
@property(nonatomic,readonly) CGFloat majorRadiusTolerance API_AVAILABLE(ios(8.0));

@property(nullable,nonatomic,readonly,strong) UIWindow                        *window;
@property(nullable,nonatomic,readonly,strong) UIView                          *view;
@property(nullable,nonatomic,readonly,copy)   NSArray <UIGestureRecognizer *> *gestureRecognizers API_AVAILABLE(ios(3.2));

@property(nonatomic, readonly, nullable) UIResponder *nextResponder;

@property(nonatomic, readonly) BOOL canBecomeFirstResponder;    // default is NO
- (BOOL)becomeFirstResponder;

@property(nonatomic, readonly) BOOL canResignFirstResponder;    // default is YES
- (BOOL)resignFirstResponder;

@property(nonatomic, readonly) BOOL isFirstResponder;

// 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;
- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event;
- (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event;
- (void)touchesCancelled:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event;
- (void)touchesEstimatedPropertiesUpdated:(NSSet<UITouch *> *)touches API_AVAILABLE(ios(9.1));

// Generally, all responders which do custom press handling should override all four of these methods.
// Your responder will receive either pressesEnded:withEvent or pressesCancelled:withEvent: for each
// press it is handling (those presses it received in pressesBegan:withEvent:).
// pressesChanged:withEvent: will be invoked for presses that provide an analog value
// (like thumbsticks or analog push buttons)
// *** You must handle cancelled presses to ensure correct behavior in your application.  Failure to
// do so is very likely to lead to incorrect behavior or crashes.
- (void)pressesBegan:(NSSet<UIPress *> *)presses withEvent:(nullable UIPressesEvent *)event API_AVAILABLE(ios(9.0));
- (void)pressesChanged:(NSSet<UIPress *> *)presses withEvent:(nullable UIPressesEvent *)event API_AVAILABLE(ios(9.0));
- (void)pressesEnded:(NSSet<UIPress *> *)presses withEvent:(nullable UIPressesEvent *)event API_AVAILABLE(ios(9.0));
- (void)pressesCancelled:(NSSet<UIPress *> *)presses withEvent:(nullable UIPressesEvent *)event API_AVAILABLE(ios(9.0));

- (void)motionBegan:(UIEventSubtype)motion withEvent:(nullable UIEvent *)event API_AVAILABLE(ios(3.0));
- (void)motionEnded:(UIEventSubtype)motion withEvent:(nullable UIEvent *)event API_AVAILABLE(ios(3.0));
- (void)motionCancelled:(UIEventSubtype)motion withEvent:(nullable UIEvent *)event API_AVAILABLE(ios(3.0));

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event;
- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event;

- (nullable UIView *)hitTest:(CGPoint)point withEvent:(nullable UIEvent *)event {
//判断是否合格
if (!self.hidden && self.alpha > 0.01 && self.isUserInteractionEnabled) {
//判断点击位置是否在自己区域内部
if ([self pointInside: point withEvent:event]) {

            UIView *attachedView;
for (int i = self.subviews.count - 1; i >= 0; i--) {

                UIView *view  = self.subviews[i];
//对子view进行hitTest

                attachedView =  [view hitTest:point withEvent:event];
if (attachedView)
break;

            }
if (attachedView)  {
return attachedView;

            } else {
return self;

            }

        }

    }
return nil;

}