UIView 子类没有接收到 touchesBegan、touchesEnded

Question

好的，所以我有一个应用程序，它是 UIView 的子类，并且依赖于 touchesBegan 和 touchesEnded。我当然指的是这些回调：

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event

前几天我将我的 iOS 从 7 更新到了 9（我知道，我很懒），发现触摸不起作用。原来上面的函数没有在我的 UIView 子类中被调用。好奇，我开始了一个空白项目，足够短，我就在这里发布代码。

main.m:

#import <UIKit/UIKit.h>
#import "AppDelegate.h"

int main(int argc, char * argv[]) {
    @autoreleasepool {
        return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
    }
}

这里是 AppDelegate。动态创建窗口和视图。

#import "AppDelegate.h"
#import "SubView.h"

@implementation AppDelegate


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.

    //create a window and give it a frame. makeKeyAndVisible
    CGRect rect = [[UIScreen mainScreen] bounds];
    self.window = [[UIWindow alloc] initWithFrame:rect];
    self.window.frame = [[UIScreen mainScreen] bounds];
    [self.window makeKeyAndVisible];

    //Create a subview. Make it a red square. make sure it has a background.
    //set the userInteractionEnabled and multipleTouchEnabled and for
    //good meausure call becomeFirstResponder.
    SubView *view = [[SubView alloc] initWithFrame:CGRectMake(100,100,100,100)];
    view.backgroundColor = [UIColor redColor];
    [self.window addSubview:view];
    view.userInteractionEnabled = YES;
    view.multipleTouchEnabled = YES;
    [view becomeFirstResponder];


    //Create default UIViewControllers because Objective-C fails if the windows don't have
    //root view controllers. I don't like being muscled into MVC but what are you gonna do
    NSArray *windows = [[UIApplication sharedApplication] windows];
    for(UIWindow *window in windows) {
        if(window.rootViewController == nil){
            UIViewController* vc = [[UIViewController alloc]initWithNibName:nil bundle:nil];
            window.rootViewController = vc;
            window.userInteractionEnabled = YES;
            window.multipleTouchEnabled = YES;
        }
    }

return YES;
}

@end

这里是 SubView 类。只是有touchesBegan touchesEnded。

子视图.h

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
@interface SubView : UIView {
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event;

@end

子视图.m

#import "SubView.h"

@implementation SubView

//delegate method for touches began
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

    //[super touchesBegan:touches withEvent:event];
    NSLog(@"touchesBegan!");

}


//delegate method for touches ending.
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {

    //[super touchesEnded:touches withEvent:event];
    NSLog(@"touchesEnded!");
}

//just for good measure.
- (BOOL) canBecomeFirstResponder {
    return YES;
}

@end

很简单。创建窗口，创建SubView，将SubView添加到窗口，设置userInteractionEnabled。然而，它不起作用。我看过以下 S.O.帖子：

subviews are not receiving touches

iPhone SDK - Forwarding touches from a UIViewController to a subview

touchesBegan not responding

touchesBegan in UIView not being called

touchesBegan not called in UIView subclass

touchesBegan not called in a UIView subclass

他们都说 userInteractionEnabled = YES 应该修复它，或者可能有视图覆盖另一个视图，或者视图可能有透明背景。这些都不适用这里。我设置了 view.userInteractionEnabled = YES，我什至尝试给视图提供第一响应者状态。这些似乎都没有任何好处。

精明的观察者也会看到我在窗口本身上设置了这些值：

window.userInteractionEnabled = YES;
window.multipleTouchEnabled = YES;

我试过有无。没有骰子。我试过打电话

[super touchesBegan:touches withEvent:event]

和

[super touchesEnded:touches withEvent:event]

在 SubView 的那些回调中。没有骰子。您能给我的任何帮助将不胜感激。谢谢！

Answer 1

在应用运行时查看您的视图层次结构，可以使用recursiveDescription 或使用 Xcode 7 的“调试视图层次结构”按钮。

(lldb) po [[[UIApplication sharedApplication] keyWindow] recursiveDescription]
<UIWindow: 0x7fc1f9d17b20; frame = (0 0; 414 736); gestureRecognizers = <NSArray: 0x7fc1f9d18910>; layer = <UIWindowLayer: 0x7fc1f9d16560>>
   | <SubView: 0x7fc1f9c04350; frame = (100 100; 100 100); layer = <CALayer: 0x7fc1f9c04730>>
   | <UIView: 0x7fc1f9c07500; frame = (0 0; 414 736); autoresize = W+H; layer = <CALayer: 0x7fc1f9c07fc0>>

子视图列表中后面的视图“更接近”屏幕，因此首先接收触摸。由通用UIViewController 创建的视图填满了窗口，并且位于您的SubView 前面。因此您的SubView 无法接收到触摸。

Apple 在五年前的 iOS 4.0 中将 rootViewController 属性添加到了 UIWindow。与它抗争，你只会给自己找麻烦。只需让rootViewController.view 成为您窗口中的单个顶级视图，并在其下添加您的子视图。没有人会强迫您将任何其他视图控制器添加到您的应用中。