Question

当我的视图控制器被从导航堆栈中推出或弹出时，我需要做某些事情，但是不想使用viewillappear / viewdidappear或viewwilldisappear / viewdiddisappear，因为除了推送/弹出视图控制器之外的那些情况。是正确的方法去使用navigationcontroller委托和navigationController：didShowViewController：animated：和navigationController：willShowViewController：animated：？如果没有，最好的方法是什么？

Answer 1

要了解它何时被推动，您可以使用

UINavigationControllerDelegate

并实施

- (void)navigationController:(UINavigationController *)navigationController 
      willShowViewController:(UIViewController *)viewController
                    animated:(BOOL)animated

只要将viewcontroller推入导航堆栈，并且每次弹出顶部的viewcontroller，就会触发此方法，从而再次显示它。因此，您必须使用一个标志来确定它是否已经初始化，如果它没有意味着它刚被推送。

要了解它何时被弹出，请使用以下答案：

viewWillDisappear: Determine whether view controller is being popped or is showing a sub-view controller

Answer 2

您可以尝试在对象推送或从导航控制器堆栈中弹出时调用的UINavigationController委托方法。

- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated;
- (void)navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL)animated;

Answer 3

这是一个示例，通过覆盖-viewWillAppear:并通过覆盖-viewWillDisappear:

来检测何时将视图控制器推入导航堆栈

-(void) viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
    if (self.isMovingToParentViewController) {
        NSLog(@"view controller being pushed");        
    }
}

-(void) viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
    if (self.isMovingFromParentViewController) {
        NSLog(@"view controller being popped");
    }
}

Answer 4

您始终可以创建UINavigationController的简单子类并包装其超类的方法，以便在调用它们之前设置一个标志：

ActionNavigationController.h

#import <UIKit/UIKit.h>

@interface ActionNavigationController : UINavigationController
@property (nonatomic, readonly) BOOL pushing;
@end

ActionNavigationController.m

#import "ActionNavigationController.h"

@implementation ActionNavigationController
@synthesize pushing = _pushing;

-(void)pushViewController:(UIViewController *)viewController 
                 animated:(BOOL)animated {
    _pushing = YES;
    [super pushViewController:viewController animated:animated];
}

- (UIViewController *)popViewControllerAnimated:(BOOL)animated {
    _pushing = NO;
    return [super popViewControllerAnimated:animated];
}
- (NSArray *)popToViewController:(UIViewController *)viewController 
                        animated:(BOOL)animated {
    _pushing = NO;
    return [super popToViewController:viewController animated:animated];
}
- (NSArray *)popToRootViewControllerAnimated:(BOOL)animated {
    _pushing = NO;
    return [super popToRootViewControllerAnimated:animated];
}

@end

如果pushing事件没有发生，NO将评估为{{1}}事件，预计将从UINavigationControllerDelegate访问此代码。

Answer 5

小心使用

- (void)navigationController:(UINavigationController *)navigationController 
  willShowViewController:(UIViewController *)viewController
                animated:(BOOL)animated

如果用户从边缘向右滑动以弹出视图控制器（而不是实际弹出它），它将调用上面的委托函数但不会调用函数

- (void)navigationController:(UINavigationController *)navigationController 
   didShowViewController:(UIViewController *)viewController 
                animated:(BOOL)animated;

请参阅https://gist.github.com/nonamelive/9334458

Answer 6

你可以在willShowViewController

中做类似的事情

func navigationController(navigationController: UINavigationController, willShowViewController viewController: UIViewController, animated: Bool) {
    if self.navigationController!.viewControllers.contains(self){
        print ("push")
    } else {
        print ("pop")
    }
}

Answer 7

（无效）navigationController：（UINavigationController *）navigationController willShowViewController：（UIViewController *）viewController 动画：（BOOL）动画；
（无效）navigationController：（UINavigationController *）navigationController didShowViewController：（UIViewController *）viewController 动画：（BOOL）动画；

这些委托函数不能在iOS13设备（与Xcode 11编译）上调用。这是一个错误吗？

Answer 8

不好的做法是将委托设置为导航控制器层次结构中的某个内容，而不要注意通知：

UINavigationControllerWillShowViewControllerNotification

UINavigationControllerDidShowViewControllerNotification

并且userInfo对象包含“ NextVisible”和“ LastVisible”视图控制器。但是，在外观方法中使用isMoving可能是最好的方法。

如何从导航堆栈中推送/弹出uiviewcontroller时收到警报

8 个答案: