事件响应链

（1）设置根视图控制器

（2）RootViewController.m

- (void)viewDidLoad
{
    [super viewDidLoad];

    MyView *view = [[MyView alloc] initWithFrame:CGRectMake(0, 20, 320, 300)];
    view.backgroundColor = [UIColor grayColor];
    [self.view addSubview:view];
    
}

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

    NSLog(@"viewCtrl touchesBegan");
    
    [self.nextResponder touchesBegan:touches withEvent:event];
}

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

    NSLog(@"myView touchesBegan");
    
    //将事件传递给下一个响应者
    /*
     nextResponder可以取得下一个响应者
     */
    [self.nextResponder touchesBegan:touches withEvent:event];
}

//window分发事件的方法
- (void)sendEvent:(UIEvent *)event {

    NSLog(@"window sendEvent");
    
    [super sendEvent:event];
    
}

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

    NSLog(@"window touchesBegan");
    
}