在导航控制器中设置后退按钮的操作

Setting action for back button in navigation controller(在导航控制器中设置后退按钮的操作)

问题描述

我正在尝试覆盖导航控制器中后退按钮的默认操作.我在自定义按钮上提供了一个目标操作.奇怪的是，当通过 backbutton 属性分配它时，它不会注意它们，它只是弹出当前视图并返回到根:

I'm trying to overwrite the default action of the back button in a navigation controller. I've provided a target an action on the custom button. The odd thing is when assigning it though the backbutton attribute it doesn't pay attention to them and it just pops the current view and goes back to the root:

UIBarButtonItem *backButton = [[UIBarButtonItem alloc] 
                                  initWithTitle: @"Servers" 
                                  style:UIBarButtonItemStylePlain 
                                  target:self 
                                  action:@selector(home)];
self.navigationItem.backBarButtonItem = backButton;

只要我通过 navigationItem 上的 leftBarButtonItem 设置它，它就会调用我的操作，但是按钮看起来像一个普通的圆形按钮，而不是带箭头的返回按钮:

As soon as I set it through the leftBarButtonItem on the navigationItem it calls my action, however then the button looks like a plain round one instead of the arrowed back one:

self.navigationItem.leftBarButtonItem = backButton;

如何让它在返回根视图之前调用我的自定义操作?有没有办法覆盖默认的后退操作，或者有没有在离开视图时总是调用的方法(viewDidUnload 不这样做)?

How can I get it to call my custom action before going back to the root view? Is there a way to overwrite the default back action, or is there a method that is always called when leaving a view (viewDidUnload doesn't do that)?

推荐答案

试着把它放到你想要检测压力的视图控制器中:

Try putting this into the view controller where you want to detect the press:

-(void) viewWillDisappear:(BOOL)animated {
    if ([self.navigationController.viewControllers indexOfObject:self]==NSNotFound) {
       // back button was pressed.  We know this is true because self is no longer
       // in the navigation stack.  
    }
    [super viewWillDisappear:animated];
}

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