iOS Touch以及事件响应链（一）hit-testing

简介

本文的目的是让读者彻底了解，iOS系统是如何识别Touch事件，以及如何传递对应的事件到指定的View

iOS事件主要分为四种

  1. touch事件
  2. 运动事件
  3. 远程事件
  4. 按压事件
    参见UIEvent的type属性
typedef NS_ENUM(NSInteger, UIEventType) {
    UIEventTypeTouches,
    UIEventTypeMotion,
    UIEventTypeRemoteControl,
    UIEventTypePresses NS_ENUM_AVAILABLE_IOS(9_0),
};
1480993244519.png

这里只介绍第一种Touch事件

为了便于区分把TouchEvent的
touchesBegan:withEvent:叫做Touch,手势类型的叫Gesture.

TouchEvent.png

事件处理流程

  1. App(DemoTSAplication类，UIApplication子类，代表当前应用)先通过hit-testing找到touch View.
  2. 而后APP收到sendEvent:事件，传递给Window(TSWindow)的sendEvent:,由TSWindow分解成touchesBegan:withEvent：，touchesMoved:withEvent,touchesEnd:withEvent,touchesCancel:withEvent等事件。
  3. 具体的手势识别以及Target-Action在TSWindow的sendEvent:收到Touch Event状态的UITouchPhaseBegan与UITouchPhaseEnded|UITouchPhaseCancelled之间进行。

解析UITapGestureRecognizer

  • UIGestureRecognizer不入响应链

UIGestureRecognizer objects are not in the responder chain, yet observe touches hit-tested to their view and their view's subviews.

原理

触摸事件(Touch events)主要用两步实现的

第一步：碰撞测试(hit-testing)

要响应一个触摸事件，先要找到触摸的是哪个View,再根据Next Response来找到合适的处理方法

碰撞测试原理

  1. hit-testing通过UIView的hitTest:withEvent:找到对应的触摸的View。
  2. hitTest:withEvent:内部会调用本类pointInside:withEvent:，pointInside:withEvent:返回bool值，来确定是否点击范围在本View范围内。
  3. 如果在，倒序递归调用所有subviews的同一过程,只要找到最后一层 调用pointInside:withEvent:返回YES,没有subview或者subview的pointInside:withEvent:返回为nil，则返回self，并逐级返回到顶层。 找到之后并不继续进行递归。

至于为什么hitTest:withEvent:在一个点击事件里调用两遍，还不知道为什么

举个例子

Demo截屏

截屏2016_12_8_上午9_51.png

当前controller叫hit-testing,controller对应的view叫AView,AView第一个子View叫BView,BView有一个唯一子ViewCView,AView第二个子View叫DView,DView没有子View。以此界面，来分析hit-testing

点击AView

时序图

SequenceDiagram2.jpg

时序图的步骤在一次touch调用了2遍，看日志，原因未知，没有查到资料。

日志

2016-12-08 11:00:07.546 TSEventDemo[35550:1352018] -[TSWindow hitTest:withEvent:] Before
2016-12-08 11:00:07.547 TSEventDemo[35550:1352018] -[TSWindow pointInside:withEvent:] Before
2016-12-08 11:00:07.547 TSEventDemo[35550:1352018] -[TSWindow pointInside:withEvent:] After
2016-12-08 11:00:07.547 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:AView(MainView)] Before
2016-12-08 11:00:07.548 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:AView(MainView)] Before
2016-12-08 11:00:07.548 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:AView(MainView)] After
2016-12-08 11:00:07.548 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:DView] Before
2016-12-08 11:00:07.548 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:DView] Before
2016-12-08 11:00:07.549 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:DView] After
2016-12-08 11:00:07.549 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:DView] After
2016-12-08 11:00:07.549 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:BView] Before
2016-12-08 11:00:07.549 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:BView] Before
2016-12-08 11:00:07.550 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:BView] After
2016-12-08 11:00:07.550 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:BView] After
2016-12-08 11:00:07.550 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:AView(MainView)] After
2016-12-08 11:00:07.551 TSEventDemo[35550:1352018] -[TSWindow hitTest:withEvent:] After
2016-12-08 11:00:07.551 TSEventDemo[35550:1352018] -[TSWindow hitTest:withEvent:] Before
2016-12-08 11:00:07.551 TSEventDemo[35550:1352018] -[TSWindow pointInside:withEvent:] Before
2016-12-08 11:00:07.551 TSEventDemo[35550:1352018] -[TSWindow pointInside:withEvent:] After
2016-12-08 11:00:07.552 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:AView(MainView)] Before
2016-12-08 11:00:07.552 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:AView(MainView)] Before
2016-12-08 11:00:07.552 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:AView(MainView)] After
2016-12-08 11:00:07.552 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:DView] Before
2016-12-08 11:00:07.553 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:DView] Before
2016-12-08 11:00:07.553 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:DView] After
2016-12-08 11:00:07.553 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:DView] After
2016-12-08 11:00:07.553 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:BView] Before
2016-12-08 11:00:07.553 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:BView] Before
2016-12-08 11:00:07.554 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:BView] After
2016-12-08 11:00:07.554 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:BView] After
2016-12-08 11:00:07.554 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:AView(MainView)] After
2016-12-08 11:00:07.554 TSEventDemo[35550:1352018] -[TSWindow hitTest:withEvent:] After

第一遍调试堆栈

![TSWindow_m1.png](http://upload-images.jianshu.io/upload_images/3134371-057baa6e9a3c9e17.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)

第二遍调试堆栈

解析:

  1. 第一个收到hitTest:withEvent:肯定是TSWindow,TSWindow调用pointInside:withEvent:返回YES，代表点击在TSWindows上，倒序递归遍历TSWindowsubviews。
  2. 只有一个子ViewAView,调用AView的pointInside:withEvent:返回YES，倒序递归遍历AViewsubviews.
  3. 先遍历DView,调用DView的pointInside:withEvent:返回NO,DView的hitTest:withEvent:返回nil。
  4. 再遍历BView,,调用BView的pointInside:withEvent:返回NO,BView的hitTest:withEvent:返回nil。
  5. AView所有子View都返回nil了，就返回self.
点击DView

时序图

SequenceDiagram3.jpg

日志

2016-12-08 14:30:34.886 TSEventDemo[35550:1352018] -[TSWindow hitTest:withEvent:] Before
2016-12-08 14:30:34.886 TSEventDemo[35550:1352018] -[TSWindow pointInside:withEvent:] Before
2016-12-08 14:30:34.886 TSEventDemo[35550:1352018] -[TSWindow pointInside:withEvent:] After
2016-12-08 14:30:34.887 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:AView(MainView)] Before
2016-12-08 14:30:34.887 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:AView(MainView)] Before
2016-12-08 14:30:34.888 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:AView(MainView)] After
2016-12-08 14:30:34.888 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:DView] Before
2016-12-08 14:30:34.888 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:DView] Before
2016-12-08 14:30:34.888 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:DView] After
2016-12-08 14:30:34.889 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:DView] After
2016-12-08 14:30:34.889 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:AView(MainView)] After
2016-12-08 14:30:34.889 TSEventDemo[35550:1352018] -[TSWindow hitTest:withEvent:] After
2016-12-08 14:30:34.890 TSEventDemo[35550:1352018] -[TSWindow hitTest:withEvent:] Before
2016-12-08 14:30:34.890 TSEventDemo[35550:1352018] -[TSWindow pointInside:withEvent:] Before
2016-12-08 14:30:34.890 TSEventDemo[35550:1352018] -[TSWindow pointInside:withEvent:] After
2016-12-08 14:30:34.890 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:AView(MainView)] Before
2016-12-08 14:30:34.891 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:AView(MainView)] Before
2016-12-08 14:30:34.891 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:AView(MainView)] After
2016-12-08 14:30:34.891 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:DView] Before
2016-12-08 14:30:34.891 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:DView] Before
2016-12-08 14:30:34.892 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:DView] After
2016-12-08 14:30:34.892 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:DView] After
2016-12-08 14:30:34.892 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:AView(MainView)] After
2016-12-08 14:30:34.892 TSEventDemo[35550:1352018] -[TSWindow hitTest:withEvent:] After
点击BView

时序图

SequenceDiagram4.jpg

日志

2016-12-08 15:19:16.611 TSEventDemo[35550:1352018] -[TSWindow hitTest:withEvent:] Before
2016-12-08 15:19:16.612 TSEventDemo[35550:1352018] -[TSWindow pointInside:withEvent:] Before
2016-12-08 15:19:16.612 TSEventDemo[35550:1352018] -[TSWindow pointInside:withEvent:] After
2016-12-08 15:19:16.613 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:AView(MainView)] Before
2016-12-08 15:19:16.614 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:AView(MainView)] Before
2016-12-08 15:19:16.614 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:AView(MainView)] After
2016-12-08 15:19:16.615 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:DView] Before
2016-12-08 15:19:16.615 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:DView] Before
2016-12-08 15:19:16.616 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:DView] After
2016-12-08 15:19:16.616 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:DView] After
2016-12-08 15:19:16.617 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:BView] Before
2016-12-08 15:19:16.617 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:BView] Before
2016-12-08 15:19:16.617 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:BView] After
2016-12-08 15:19:16.618 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:CView] Before
2016-12-08 15:19:16.618 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:CView] Before
2016-12-08 15:19:16.619 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:CView] After
2016-12-08 15:19:16.619 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:CView] After
2016-12-08 15:19:16.620 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:BView] After
2016-12-08 15:19:16.620 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:AView(MainView)] After
2016-12-08 15:19:16.621 TSEventDemo[35550:1352018] -[TSWindow hitTest:withEvent:] After
2016-12-08 15:19:16.621 TSEventDemo[35550:1352018] -[TSWindow hitTest:withEvent:] Before
2016-12-08 15:19:16.622 TSEventDemo[35550:1352018] -[TSWindow pointInside:withEvent:] Before
2016-12-08 15:19:16.622 TSEventDemo[35550:1352018] -[TSWindow pointInside:withEvent:] After
2016-12-08 15:19:16.623 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:AView(MainView)] Before
2016-12-08 15:19:16.623 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:AView(MainView)] Before
2016-12-08 15:19:16.623 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:AView(MainView)] After
2016-12-08 15:19:16.624 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:DView] Before
2016-12-08 15:19:16.624 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:DView] Before
2016-12-08 15:19:16.625 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:DView] After
2016-12-08 15:19:16.625 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:DView] After
2016-12-08 15:19:16.625 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:BView] Before
2016-12-08 15:19:16.625 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:BView] Before
2016-12-08 15:19:16.626 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:BView] After
2016-12-08 15:19:16.626 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:CView] Before
2016-12-08 15:19:16.626 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:CView] Before
2016-12-08 15:19:16.627 TSEventDemo[35550:1352018] -[TSView pointInside:withEvent:] [name:CView] After
2016-12-08 15:19:16.627 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:CView] After
2016-12-08 15:19:16.628 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:BView] After
2016-12-08 15:19:16.628 TSEventDemo[35550:1352018] -[TSView hitTest:withEvent:] [name:AView(MainView)] After
2016-12-08 15:19:16.628 TSEventDemo[35550:1352018] -[TSWindow hitTest:withEvent:] After

解析
不再解析，总结成一句话：

倒序递归subview,直到某个子ViewpointInside:withEvent:返回YES,没有subview或者subviews的hitTest:withEvent:返回nil,则返回self.

点击CView

用提供的Demo，自验看日志，即可。

模拟代码

发现用文字流程图对程序员来说，还没代码更直观。故附上模拟代码

伪代码

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
{
    if (self.hidden || !self.userInteractionEnabled || self.alpha < 0.01 || ![self pointInside:point withEvent:event] || ![self _isAnimatedUserInteractionEnabled]) {
        return nil;
    } else {
        for (UIView *subview in [self.subviews reverseObjectEnumerator]) {
            UIView *hitView = [subview hitTest:[subview convertPoint:point fromView:self] withEvent:event];
            if (hitView) {
                return hitView;
            }
        }
        return self;
    }
}

Demo代码

放在第二篇

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