如何从导航堆栈中推送/弹出uiviewcontroller时收到警报

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，还包括这些情况。是正确的方法去使用navigationcontroller委托和navigationController：didShowViewController：animated：和navigationController：willShowViewController：animated：？如果没有，最好的办法是什么？

Answer 1

要知道什么时候推，你可以使用

UINavigationControllerDelegate

并实施

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

只要将viewcontroller推入导航堆栈，并且每当弹出顶部的viewcontroller时，此方法就会触发，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只是被推动了。

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，通过重写-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：

Action NavigationController.h

#import <UIKit/UIKit.h>

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

行动NavigationController.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

由于pushing将评估NO事件，如果没有发生任何事情，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而不是下面的函数

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

请参考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")
    }
}