iOS基础补完计划--透过堆栈看事件响应机制

目录

• 前言
• TouchEvent 响应链
• UIControl
• UIGestureRecognizer
• 结论

前言

众所周知、手势识别器的权限比响应链更高。
而UIControl的响应机制不涉及响应链、由UIAPPlication直接分发。

于是、会出现一些冲突的问题。
比如给self.view添加手势之后、cell不可点击、但UIButton不受影响。
可以看看《iOS点击事件和手势冲突》。

而在网上找了找、诸如《iOS触摸事件全家桶》/《iOS触摸》以及官方文档都进行了解释、但总觉得不那么直观。

TouchEvent 响应链

点击一个View

frame #20: 0x000000010ce0e4fd NSObject`-[View1 touchesBegan:withEvent:](self=0x00007f9c19e20a10, _cmd="touchesBegan:withEvent:", touches=1 element, event=0x000060400010d410) at View1.m:107
frame #21: 0x000000010ec87e1a UIKit`-[UIWindow _sendTouchesForEvent:] + 2052
frame #22: 0x000000010ec897c1 UIKit`-[UIWindow sendEvent:] + 4086
frame #23: 0x000000010ec2d310 UIKit`-[UIApplication sendEvent:] + 352

• 结论

响应链由UIWindow的_sendTouchesForEvent方法调起。
而_sendTouchesForEvent由sendEvent:方法调起。

UIControl

点击一个UIButton

• UIButton响应线

frame #0: 0x000000010ce0d2a7 NSObject`-[ViewController btnClick](self=0x00007f9c19f0f080, _cmd="btnClick") at ViewController.m:55
frame #1: 0x000000010ec133e8 UIKit`-[UIApplication sendAction:to:from:forEvent:] + 83
frame #2: 0x000000010ed8e7a4 UIKit`-[UIControl sendAction:to:forEvent:] + 67
frame #3: 0x000000010ed8eac1 UIKit`-[UIControl _sendActionsForEvents:withEvent:] + 450
frame #4: 0x000000010ed8da09 UIKit`-[UIControl touchesEnded:withEvent:] + 580
frame #5: 0x000000010ec880bf UIKit`-[UIWindow _sendTouchesForEvent:] + 2729
frame #6: 0x000000010ec897c1 UIKit`-[UIWindow sendEvent:] + 4086
frame #7: 0x000000010ec2d310 UIKit`-[UIApplication sendEvent:] + 352

• 响应链开始线

frame #0: 0x000000010c9db48b NSObject`-[View1 touchesBegan:withEvent:](self=0x00007f8a15405cc0, _cmd="touchesBegan:withEvent:", touches=1 element, event=0x00006000001044a0) at View1.m:109
frame #1: 0x000000010e854e1a UIKit`-[UIWindow _sendTouchesForEvent:] + 2052
frame #2: 0x000000010e8567c1 UIKit`-[UIWindow sendEvent:] + 4086
frame #3: 0x000000010e7fa310 UIKit`-[UIApplication sendEvent:] + 352

• 响应链结束线

frame #0: 0x000000010c9db60b NSObject`-[View1 touchesEnded:withEvent:](self=0x00007f8a15405cc0, _cmd="touchesEnded:withEvent:", touches=1 element, event=0x00006000001044a0) at View1.m:120
frame #1: 0x000000010e8550bf UIKit`-[UIWindow _sendTouchesForEvent:] + 2729
frame #2: 0x000000010e8567c1 UIKit`-[UIWindow sendEvent:] + 4086
frame #3: 0x000000010e7fa310 UIKit`-[UIApplication sendEvent:] + 352

• 结论

依旧会由UIWindow的_sendTouchesForEvent:调起响应链。
但是与普通UIView不同的是UIControl在touchesEnded:withEvent时、会结束响应链。
然后直接由UIApplication向其发送Action事件。

UIGestureRecognizer

点击一个添加了手势的View或者SubView

• 手势响应线

frame #0: 0x00000001034ea447 NSObject`-[ViewController doTapChange](self=0x00007fbb31607910, _cmd="doTapChange") at ViewController.m:101
frame #1: 0x00000001058e754f UIKit`-[UIGestureRecognizerTarget _sendActionWithGestureRecognizer:] + 57
frame #2: 0x00000001058f0324 UIKit`_UIGestureRecognizerSendTargetActions + 109
frame #3: 0x00000001058edb6c UIKit`_UIGestureRecognizerSendActions + 307
frame #4: 0x00000001058ecdc0 UIKit`-[UIGestureRecognizer _updateGestureWithEvent:buttonEvent:] + 859
frame #5: 0x00000001058d1e24 UIKit`_UIGestureEnvironmentUpdate + 1329
frame #6: 0x00000001058d18a7 UIKit`-[UIGestureEnvironment _deliverEvent:toGestureRecognizers:usingBlock:] + 484
frame #7: 0x00000001058d09a9 UIKit`-[UIGestureEnvironment _updateGesturesForEvent:window:] + 281
frame #8: 0x00000001053667ab UIKit`-[UIWindow sendEvent:] + 4064
frame #9: 0x000000010530a310 UIKit`-[UIApplication sendEvent:] + 352

• 响应链开始线

[ViewController touchesBegan:withEvent:](self=0x00007f8a15426010, _cmd="touchesBegan:withEvent:", touches=1 element, event=0x00006000001044a0) at ViewController.m:97
frame #1: 0x000000010ea0c767 UIKit`forwardTouchMethod + 340
frame #2: 0x000000010ea0c602 UIKit`-[UIResponder touchesBegan:withEvent:] + 49
frame #3: 0x000000010e854e1a UIKit`-[UIWindow _sendTouchesForEvent:] + 2052
frame #4: 0x000000010e8567c1 UIKit`-[UIWindow sendEvent:] + 4086
frame #5: 0x000000010e7fa310 UIKit`-[UIApplication sendEvent:] + 352

• 响应链取消线

frame #0: 0x00000001034eb5ed NSObject`-[View1 touchesCancelled:withEvent:](self=0x00007fbb314061e0, _cmd="touchesCancelled:withEvent:", touches=0x000060400025a1f0, event=0x000060000011d0a0) at View1.m:120
frame #1: 0x0000000105303434 UIKit`__98-[UIApplication _cancelViewProcessingOfTouches:withEvent:sendingTouchesCancelledToViewsOfTouches:]_block_invoke + 663
frame #2: 0x0000000105302c22 UIKit`-[UIApplication _cancelTouches:withEvent:includingGestures:notificationBlock:] + 1091
frame #3: 0x0000000105303167 UIKit`-[UIApplication _cancelViewProcessingOfTouches:withEvent:sendingTouchesCancelledToViewsOfTouches:] + 158
frame #4: 0x00000001058d41e8 UIKit`_UIGestureEnvironmentCancelTouches + 687
frame #5: 0x00000001058d3f26 UIKit`-[UIGestureEnvironment _cancelTouches:event:] + 42
frame #6: 0x00000001058ed2d0 UIKit`-[UIGestureRecognizer _updateGestureWithEvent:buttonEvent:] + 2155
frame #7: 0x00000001058d1e24 UIKit`_UIGestureEnvironmentUpdate + 1329
frame #8: 0x00000001058d18a7 UIKit`-[UIGestureEnvironment _deliverEvent:toGestureRecognizers:usingBlock:] + 484
frame #9: 0x00000001058d09a9 UIKit`-[UIGestureEnvironment _updateGesturesForEvent:window:] + 281
frame #10: 0x00000001053667ab UIKit`-[UIWindow sendEvent:] + 4064
frame #11: 0x000000010530a310 UIKit`-[UIApplication sendEvent:] + 352

• 结论

响应链的开始依旧由UIWindow的_sendTouchesForEvent触发。
但是在sendEvent时、进行了手势判断。
如果成功识别了手势、则取消响应链
并且向Target发送Action。

结论

有几个地方可以提一下:

1. 响应链本身什么都不做
   所以手势以及UIControl的处理本身并不依赖响应链

2. 响应链必然会触发、只是后期处理不一样。
   如果是手势、则被取消。如果是UIControl则被结束。

• 关于事件处理的优先级。

这个光看堆栈应该是看不出来的。
但结合一些结论、可以试着猜测：

1. 目标View上有手势
   手势优先识别
2. 目标View上没有手势但是归属系统UIControl
   UIControl优先处理
3. 目标View就是个普通View(或者自定义的Control)
   下层手势优先识别、如果没有手势/识别失败则交给响应链

• 如何将事件发送给指定的View/手势

全部依赖UITouch的属性

1. Window

@property(nullable,nonatomic,readonly,strong) UIWindow *window;

2. 响应链/UIControl

@property(nullable,nonatomic,readonly,strong) UIView *view;

3. 手势

@property(nullable,nonatomic,readonly,copy)   NSArray <UIGestureRecognizer *> *gestureRecognizers NS_AVAILABLE_IOS(3_2);

最后

本文主要是自己的学习与总结。如果文内存在纰漏、万望留言斧正。如果愿意补充以及不吝赐教小弟会更加感激。