viewWillDisappear：确定是正在弹出视图控制器还是正在显示子视图控制器

12 回答

• 226

  您可以使用以下内容 .

  - (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];
    NSArray *viewControllers = self.navigationController.viewControllers;
    if (viewControllers.count > 1 && [viewControllers objectAtIndex:viewControllers.count-2] == self) {
      // View is disappearing because a new view controller was pushed onto the stack
      NSLog(@"New view controller was pushed");
    } else if ([viewControllers indexOfObject:self] == NSNotFound) {
      // View is disappearing because it was popped from the stack
      NSLog(@"View controller was popped");
    }
  }
  

  当然，这是可能的，因为在调用viewWillDisappear时，UINavigationController的视图控制器堆栈（通过viewControllers属性公开）已经更新 .

  回复于 2024-05-20T16:56:53+08:00
• -1

  我认为最简单的方法是：

  - (void)viewWillDisappear:(BOOL)animated
  {
      [super viewWillDisappear:animated];
      if ([self isMovingFromParentViewController])
      {
          NSLog(@"View controller was popped");
      }
      else
      {
          NSLog(@"New view controller was pushed");
      }
  }
  

  迅速：

  override func viewWillDisappear(animated: Bool)
  {
      super.viewWillDisappear(animated)
      if isMovingFromParentViewController
      {
          print("View controller was popped")
      }
      else
      {
          print("New view controller was pushed")
      }
  }
  

  回复于 2024-05-20T16:56:53+08:00
• 0

  来自UIViewController.h中的Apple文档：

  “这四种方法可以在视图控制器的外观回调中使用，以确定它是作为子视图控制器呈现，关闭，还是添加或删除 . 例如，视图控制器可以检查它是否因为被解除而消失或者通过检查表达式（[self isBeingDismissed] || [self isMovingFromParentViewController]）在其viewWillDisappear：方法中询问自己 . - （BOOL）isBeingPresented NS_AVAILABLE_IOS（5_0）; - （BOOL）isBeingDismissed NS_AVAILABLE_IOS（5_0）; - （BOOL）isMovingToParentViewController NS_AVAILABLE_IOS（5_0）; - （BOOL）isMovingFromParentViewController NS_AVAILABLE_IOS（5_0）;

  所以是的，唯一记录的方法是通过以下方式：

  - (void)viewWillDisappear:(BOOL)animated
  {
      [super viewWillDisappear:animated];
      if ([self isBeingDismissed] || [self isMovingFromParentViewController]) {
      }
  }
  

  Swift 3版本：

  override func viewWillDisappear(_ animated: Bool) {
      super.viewWillDisappear(animated)
  
      if self.isBeingDismissed || self.isMovingFromParentViewController { 
      }
  }
  

  回复于 2024-05-20T16:56:53+08:00
• 17

  如果您只是想知道您的视图是否被弹出，我刚刚发现 self.navigationController 在 viewDidDisappear 中是 nil ，当它从控制器堆栈中删除时 . 所以这是一个简单的替代测试 .

  （这是我在尝试各种其他扭曲之后发现的 . 我没有导航控制器协议来注册视图控制器以便在弹出窗口上通知 . 你不能使用 UINavigationControllerDelegate ，因为它实际上是真正的显示工作 . ）

  回复于 2024-05-20T16:56:53+08:00
• 126

  斯威夫特4

  override func viewWillDisappear(_ animated: Bool)
      {
          super.viewWillDisappear(animated)
          if self.isMovingFromParent
          {
              //View Controller Popped
          }
          else
          {
              //New view controller pushed
          }
      }
  

  回复于 2024-05-20T16:56:53+08:00
• 1

  在Swift中：

  override func viewWillDisappear(animated: Bool) {
      if let navigationController = self.navigationController {
          if !contains(navigationController.viewControllers as! Array<UIViewController>, self) {
          }
      }
  
      super.viewWillDisappear(animated)
  
  }
  

  回复于 2024-05-20T16:56:53+08:00
• 55

  我发现Apple的文档很难理解 . 此扩展程序有助于查看每个导航的状态 .

  extension UIViewController {
      public func printTransitionStates() {
          print("isBeingPresented=\(isBeingPresented)")
          print("isBeingDismissed=\(isBeingDismissed)")
          print("isMovingToParentViewController=\(isMovingToParentViewController)")
          print("isMovingFromParentViewController=\(isMovingFromParentViewController)")
      }
  }
  

  回复于 2024-05-20T16:56:53+08:00
• -1

  这个问题相当陈旧，但我偶然看到它，所以我想发布最佳实践（afaik）

  你可以这样做

  if([self.navigationController.viewControllers indexOfObject:self]==NSNotFound)
   // view controller popped
  }
  

  回复于 2024-05-20T16:56:53+08:00
• 0

  这适用于 iOS7 ，不知道它是否适用于任何其他的 . 据我所知，在 viewDidDisappear 中，视图已经被弹出 . 这意味着当您查询 self.navigationController.viewControllers 时，您将获得 nil . 所以，检查一下是否为零 .

  TL; DR

  - (void)viewDidDisappear:(BOOL)animated
   {
      [super viewDidDisappear:animated];
      if (self.navigationController.viewControllers == nil) {
          // It has been popped!
          NSLog(@"Popped and Gone");
      }
   }
  

  回复于 2024-05-20T16:56:53+08:00
• 0

  在iOS 6中，Segues可以是一种非常有效的方法来处理这个问题 . 如果您在Interface Builder中为特定的segue指定了标识符，则可以在 prepareForSegue 中检查它 .

  - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
  {
      if ([segue.identifier isEqualToString:@"LoginSegue"]) {
         NSLog(@"Push");
         // Do something specific here, or set a BOOL indicating
         // a push has occurred that will be checked later
      }
  }
  

  回复于 2024-05-20T16:56:53+08:00
• 5

  我假设您的意思是当您说要推入堆栈时，通过推送新视图将视图移动到导航控制器的堆栈中 . 我建议使用 viewDidUnload 方法添加一个 NSLog 语句来向控制台写一些东西，这样你就可以看到发生了什么，你可能想要添加 NSLog 到 viewWillDissappeer .

  回复于 2024-05-20T16:56:53+08:00
• 9

  这是一个类别来完成与sbrocket的答案相同的事情：

  Header:

  #import <UIKit/UIKit.h>
  
  @interface UIViewController (isBeingPopped)
  
  - (BOOL) isBeingPopped;
  
  @end
  

  Source:

  #import "UIViewController+isBeingPopped.h"
  
  @implementation UIViewController (isBeingPopped)
  
  - (BOOL) isBeingPopped {
      NSArray *viewControllers = self.navigationController.viewControllers;
      if (viewControllers.count > 1 && [viewControllers objectAtIndex:viewControllers.count-2] == self) {
          return NO;
      } else if ([viewControllers indexOfObject:self] == NSNotFound) {
          return YES;
      }
      return NO;
  }
  
  @end
  

  回复于 2024-05-20T16:56:53+08:00