检测导航栏上按下“后退”按钮的时间 [英] Detecting when the 'back' button is pressed on a navbar

问题描述

当我在导航栏上按下后退按钮（返回上一屏幕，返回父视图）按钮时，我需要执行一些操作。

I need to perform some actions when the back button(return to previous screen, return to parent-view) button is pressed on a Navbar.

是否有一些方法我可以实现捕获事件并触发一些动作，以便在屏幕消失之前暂停和保存数据？

Is there some method I can implement to catch the event and fire off some actions to pause and save data before the screen disappears?

推荐答案

更新：根据一些评论，原始答案中的解决方案在iOS 8+的某些情况下似乎不起作用。我无法在没有进一步细节的情况下验证实际情况。

UPDATE: According to some comments, the solution in the original answer does not seem to work under certain scenarios in iOS 8+. I can't verify that that is actually the case without further details.

对于那些人而言，在那种情况下还有另一种选择。通过覆盖 willMove（toParentViewController：），可以检测何时弹出视图控制器。基本的想法是当父 nil 时，正在弹出视图控制器。

For those of you however in that situation there's an alternative. Detecting when a view controller is being popped is possible by overriding willMove(toParentViewController:). The basic idea is that a view controller is being popped when parent is nil.

查看实施容器视图控制器 了解更多详情。

自iOS 5以来，我发现处理这种情况的最简单方法正在使用新方法 - （BOOL）isMovingFromParentViewController ：

Since iOS 5 I've found that the easiest way of dealing with this situation is using the new method - (BOOL)isMovingFromParentViewController:

- (void)viewWillDisappear:(BOOL)animated {
  [super viewWillDisappear:animated];

  if (self.isMovingFromParentViewController) {
    // Do your stuff here
  }
}

- （BOOL）isMovingFromParentViewController 在推送和弹出导航堆栈中的控制器时有意义。

- (BOOL)isMovingFromParentViewController makes sense when you are pushing and popping controllers in a navigation stack.

但是，如果你要呈现模态视图控制器，你应该使用 - （BOOL）isBeingDismissed 代替：

However, if you are presenting modal view controllers you should use - (BOOL)isBeingDismissed instead:

- (void)viewWillDisappear:(BOOL)animated {
  [super viewWillDisappear:animated];

  if (self.isBeingDismissed) {
    // Do your stuff here
  }
}

如此问题所述，您可以合并这两个属性：

As noted in this question, you could combine both properties:

- (void)viewWillDisappear:(BOOL)animated {
  [super viewWillDisappear:animated];

  if (self.isMovingFromParentViewController || self.isBeingDismissed) {
    // Do your stuff here
  }
}

其他解决方案依赖于 UINavigationBar 的存在。我更喜欢这种方法，因为它从触发事件的动作中解除了执行所需的任务，即按下后退按钮。

Other solutions rely on the existence of a UINavigationBar. I like this approach more because it decouples the required tasks to perform from the action that triggered the event, i.e. pressing a back button.

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