iOS中的navigationController中的后退按钮回调

12 回答

• 159

  William Jockusch的answer用简单的技巧解决了这个问题 .

  -(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];
  }
  

  回复于 2024-05-02T21:00:25+08:00
• 7

  在我看来，最好的解决方案 .

  - (void)didMoveToParentViewController:(UIViewController *)parent
  {
      if (![parent isEqual:self.parentViewController]) {
           NSLog(@"Back pressed");
      }
  }
  

  但它只适用于iOS5

  回复于 2024-05-02T21:00:25+08:00
• 26

  覆盖后退按钮可能更好，这样您就可以在弹出视图之前处理事件，例如用户确认 .

  在viewDidLoad中创建一个UIBarButtonItem并将self.navigationItem.leftBarButtonItem设置为传递给它的sel

  - (void) viewDidLoad
  {
  // change the back button to cancel and add an event handler
  UIBarButtonItem *backButton = [[UIBarButtonItem alloc] initWithTitle:@”back”
  style:UIBarButtonItemStyleBordered
  target:self
  action:@selector(handleBack:)];
  
  self.navigationItem.leftBarButtonItem = backButton;
  [backButton release];
  
  }
  - (void) handleBack:(id)sender
  {
  // pop to root view controller
  [self.navigationController popToRootViewControllerAnimated:YES];
  
  }
  

  然后你可以做一些事情，如提升UIAlertView来确认动作，然后弹出视图控制器等 .

  或者，不是创建新的后退按钮，而是可以符合UINavigationController委托方法，以便在按下后退按钮时执行操作 .

  回复于 2024-05-02T21:00:25+08:00
• 3

  我最终得到了这个解决方案 . 当我们点击后退按钮viewDidDisappear方法调用时 . 我们可以通过调用返回true的isMovingFromParentViewController选择器来检查 . 我们可以传回数据（使用Delegate）.hope这可以帮助某人 .

  -(void)viewDidDisappear:(BOOL)animated{
  
      if (self.isMovingToParentViewController) {
  
      }
      if (self.isMovingFromParentViewController) {
         //moving back
          //pass to viewCollection delegate and update UI
          [self.delegateObject passBackSavedData:self.dataModel];
  
      }
  }
  

  回复于 2024-05-02T21:00:25+08:00
• 0

  对于“BEFORE弹出堆栈视图”：

  - (void)willMoveToParentViewController:(UIViewController *)parent{
      if (parent == nil){
          NSLog(@"do whatever you want here");
      }
  }
  

  回复于 2024-05-02T21:00:25+08:00
• 82

  这是检测此问题的正确方法 .

  - (void)willMoveToParentViewController:(UIViewController *)parent{
      if (parent == nil){
          //do stuff
  
      }
  }
  

  在推送视图时也会调用此方法 . 所以检查parent == nil是用于从堆栈弹出视图控制器

  回复于 2024-05-02T21:00:25+08:00
• 1

  有一种比询问viewControllers更合适的方法 . 您可以使控制器成为具有后退按钮的navigationBar的委托 . 这是一个例子 . 在您要处理按下后退按钮的控制器的实现中，告诉它它将实现UINavigationBarDelegate协议：

  @interface MyViewController () <UINavigationBarDelegate>
  

  然后在初始化代码中的某个地方（可能在viewDidLoad中）使您的控制器成为其导航栏的委托：

  self.navigationController.navigationBar.delegate = self;
  

  最后，实现shouldPopItem方法 . 按下后退按钮时会调用此方法 . 如果堆栈中有多个控制器或导航项，您可能想要检查哪些导航项被弹出（item参数），以便您只在预期时执行自定义操作 . 这是一个例子：

  -(BOOL)navigationBar:(UINavigationBar *)navigationBar shouldPopItem:(UINavigationItem *)item
  {
      NSLog(@"Back button got pressed!");
      //if you return NO, the back button press is cancelled
      return YES;
  }
  

  回复于 2024-05-02T21:00:25+08:00
• 4

  如果您不能使用“viewWillDisappear”或类似的方法，请尝试子类UINavigationController . 这是 Headers 类：

  #import <Foundation/Foundation.h>
  @class MyViewController;
  
  @interface CCNavigationController : UINavigationController
  
  @property (nonatomic, strong) MyViewController *viewController;
  
  @end
  

  实施班：

  #import "CCNavigationController.h"
  #import "MyViewController.h"
  
  @implementation CCNavigationController {
  
  }
  - (UIViewController *)popViewControllerAnimated:(BOOL)animated {
      @"This is the moment for you to do whatever you want"
      [self.viewController doCustomMethod];
      return [super popViewControllerAnimated:animated];
  }
  
  @end
  

  另一方面，您需要将此viewController链接到您的自定义NavigationController，因此，在常规viewController的viewDidLoad方法中执行以下操作：

  @implementation MyViewController {
      - (void)viewDidLoad
      {
          [super viewDidLoad];
          ((CCNavigationController*)self.navigationController).viewController = self;
      }
  }
  

  回复于 2024-05-02T21:00:25+08:00
• 7

  这是我实现的另一种方式（没有使用unwind segue测试它，但它可能不会像其他人在本页中的其他解决方案中所说的那样区分）让父视图控制器在子VC推送之前执行操作从视图堆栈中弹出（我从原始的UINavigationController中使用了几个级别） . 这也可以用于在推送childVC之前执行操作 . 这具有使用iOS系统后退按钮的附加优势，而不必创建自定义UIBarButtonItem或UIButton .

  • 让您的父VC采用 UINavigationControllerDelegate 协议并注册委托消息：

  MyParentViewController : UIViewController <UINavigationControllerDelegate>
  
  -(void)viewDidLoad {
      self.navigationcontroller.delegate = self;
  }
  

  • 在 MyParentViewController 中实现此 UINavigationControllerDelegate 实例方法：

  - (id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController animationControllerForOperation:(UINavigationControllerOperation)operation fromViewController:(UIViewController *)fromVC toViewController:(UIViewController *)toVC {
      // Test if operation is a pop; can also test for a push (i.e., do something before the ChildVC is pushed
      if (operation == UINavigationControllerOperationPop) {
          // Make sure it's the child class you're looking for
          if ([fromVC isKindOfClass:[ChildViewController class]]) {
              // Can handle logic here or send to another method; can also access all properties of child VC at this time
              return [self didPressBackButtonOnChildViewControllerVC:fromVC];
          }
      }
      // If you don't want to specify a nav controller transition
      return nil;
  }
  

  • 如果在上面的 UINavigationControllerDelegate 实例方法中指定了特定的回调函数

  -(id <UIViewControllerAnimatedTransitioning>)didPressBackButtonOnAddSearchRegionsVC:(UIViewController *)fromVC {
      ChildViewController *childVC = ChildViewController.new;
      childVC = (ChildViewController *)fromVC;
  
      // childVC.propertiesIWantToAccess go here
  
      // If you don't want to specify a nav controller transition
      return nil;
  

  }

  回复于 2024-05-02T21:00:25+08:00
• 1

  这是它在Swift中对我有用的东西：

  override func viewWillDisappear(_ animated: Bool) {
      if self.navigationController?.viewControllers.index(of: self) == nil {
          // back button pressed or back gesture performed
      }
  
      super.viewWillDisappear(animated)
  }
  

  回复于 2024-05-02T21:00:25+08:00
• 8

  也许它看到有人采用类似的方法，我想在这里分享一下 . 该解决方案的缺点是它需要子类化 UINavigationController . 虽然使用Method Swizzling可能有助于避免这种情况，但我没有那么做 .

  因此，默认后退按钮实际上由 UINavigationBar 管理 . 当用户点击后退按钮时， UINavigationBar 通过调用 navigationBar(_:shouldPop:) 询问其代表是否应该弹出顶部 UINavigationItem . UINavigationController 实际上实现了这一点，但它没有公开声明它采用 UINavigationBarDelegate （为什么！？） . 要拦截此事件，请创建 UINavigationController 的子类，声明其与 UINavigationBarDelegate 的一致性并实现 navigationBar(_:shouldPop:) . 如果应该弹出顶部项目，则返回 true . 返回 false 如果它应该留下来 .

  有两个问题 . 该首先，你必须在某个时候调用_26696701的 UINavigationController 版本 . 但 UINavigationBarController 没有公开声明它与 UINavigationBarDelegate 的一致性，试图调用它将导致编译时错误 . 我使用的解决方案是使用Objective-C运行时直接获取实现并调用它 . 如果有人有更好的解决方案，请告诉我 .

  另一个问题是，如果用户点击后退按钮，则首先调用 navigationBar(_:shouldPop:) ，然后调用 popViewController(animated:) . 如果通过调用 popViewController(animated:) 弹出视图控制器，则顺序会反转 . 在这种情况下，我使用布尔值来检测 navigationBar(_:shouldPop:) 之前是否调用了 popViewController(animated:) ，这意味着用户已经点击了后退按钮 .

  此外，我进行 UIViewController 的扩展，让导航控制器询问视图控制器是否应该弹出，如果用户点击后退按钮 . 视图控制器可以返回 false 并执行任何必要的操作，稍后再调用 popViewController(animated:) .

  class InterceptableNavigationController: UINavigationController, UINavigationBarDelegate {
      // If a view controller is popped by tapping on the back button, `navigationBar(_:, shouldPop:)` is called first follows by `popViewController(animated:)`.
      // If it is popped by calling to `popViewController(animated:)`, the order reverses and we need this flag to check that.
      private var didCallPopViewController = false
  
      override func popViewController(animated: Bool) -> UIViewController? {
          didCallPopViewController = true
          return super.popViewController(animated: animated)
      }
  
      func navigationBar(_ navigationBar: UINavigationBar, shouldPop item: UINavigationItem) -> Bool {
          // If this is a subsequence call after `popViewController(animated:)`, we should just pop the view controller right away.
          if didCallPopViewController {
              return originalImplementationOfNavigationBar(navigationBar, shouldPop: item)
          }
  
          // The following code is called only when the user taps on the back button.
  
          guard let vc = topViewController, item == vc.navigationItem else {
              return false
          }
  
          if vc.shouldBePopped(self) {
              return originalImplementationOfNavigationBar(navigationBar, shouldPop: item)
          } else {
              return false
          }
      }
  
      func navigationBar(_ navigationBar: UINavigationBar, didPop item: UINavigationItem) {
          didCallPopViewController = false
      }
  
      /// Since `UINavigationController` doesn't publicly declare its conformance to `UINavigationBarDelegate`,
      /// trying to called `navigationBar(_:shouldPop:)` will result in a compile error.
      /// So, we'll have to use Objective-C runtime to directly get super's implementation of `navigationBar(_:shouldPop:)` and call it.
      private func originalImplementationOfNavigationBar(_ navigationBar: UINavigationBar, shouldPop item: UINavigationItem) -> Bool {
          let sel = #selector(UINavigationBarDelegate.navigationBar(_:shouldPop:))
          let imp = class_getMethodImplementation(class_getSuperclass(InterceptableNavigationController.self), sel)
          typealias ShouldPopFunction = @convention(c) (AnyObject, Selector, UINavigationBar, UINavigationItem) -> Bool
          let shouldPop = unsafeBitCast(imp, to: ShouldPopFunction.self)
          return shouldPop(self, sel, navigationBar, item)
      }
  }
  
  extension UIViewController {
      @objc func shouldBePopped(_ navigationController: UINavigationController) -> Bool {
          return true
      }
  }
  

  在您查看控制器时，实现 shouldBePopped(_:) . 如果您没有实现此方法，则默认行为是在用户点击后退按钮时立即弹出视图控制器 .

  class MyViewController: UIViewController {
      override func shouldBePopped(_ navigationController: UINavigationController) -> Bool {
          let alert = UIAlertController(title: "Do you want to go back?",
                                        message: "Do you really want to go back? Tap on \"Yes\" to go back. Tap on \"No\" to stay on this screen.",
                                        preferredStyle: .alert)
          alert.addAction(UIAlertAction(title: "No", style: .cancel, handler: nil))
          alert.addAction(UIAlertAction(title: "Yes", style: .default, handler: { _ in
              navigationController.popViewController(animated: true)
          }))
          present(alert, animated: true, completion: nil)
          return false
      }
  }
  

  你可以看一下我的演示here .

  

  回复于 2024-05-02T21:00:25+08:00
• 3

  如果你来自push segue，你也可以覆盖 shouldPerformSegueWithIdentifier:sender: .

  回复于 2024-05-02T21:00:25+08:00