问题描述
我试图覆盖导航控制器中后退按钮的默认操作。我为自定义按钮提供了一个操作的目标。奇怪的是，当通过backbutton属性分配它时，它不注意它们，它只弹出当前视图并返回根：
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;
一旦我通过navigationItem上的leftBarButtonItem设置它就调用我的动作，看起来像一个简单的圆形，而不是一个回箭头：
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;
如何在返回根视图之前调用自定义操作？有没有办法覆盖默认的返回动作，或者有一个方法总是在离开视图时调用（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
尝试将其添加到视图控制器中以检测新闻：
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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