Question

我知道要从app委托获取当前视图控制器，我可以使用我为我的应用设置的navigationController属性。但是，在我的应用程序的许多地方都可以提供模态导航控制器。有没有办法从app委托中检测到这一点，因为当前的导航控制器将与app delegate持有引用的导航控制器不同？

Answer 1

基于gist here，我创建了一个类别来获取最顶层的视图控制器，这样调用[[UIApplication sharedApplication] topMostViewController]将为您提供应用中最顶层的视图控制器。

这在iOS 8中特别有用，其中UIAlertView和UIActionSheet已被弃用，而UIAlertController则需要在最顶层的视图控制器上显示。

的UIViewController + TopMostViewController.h

#import <UIKit/UIKit.h>

@interface UIViewController (TopMostViewController)

- (UIViewController *)topMostViewController;

@end

@interface UIApplication (TopMostViewController)

- (UIViewController *)topMostViewController;

@end

的UIViewController + TopMostViewController.m

#import "UIViewController+TopMostViewController.h"

@implementation UIViewController (TopMostViewController)

- (UIViewController *)topMostViewController
{
    if (self.presentedViewController == nil)
    {
        return self;
    }
    else if ([self.presentedViewController isKindOfClass:[UINavigationController class]])
    {
        UINavigationController *navigationController = (UINavigationController *)self.presentedViewController;
        UIViewController *lastViewController = [[navigationController viewControllers] lastObject];
        return [lastViewController topMostViewController];
    }

    UIViewController *presentedViewController = (UIViewController *)self.presentedViewController;
    return [presentedViewController topMostViewController];
}

@end

#pragma mark -

@implementation UIApplication (TopMostViewController)

- (UIViewController *)topMostViewController
{
    return [self.keyWindow.rootViewController topMostViewController];
}

@end

Answer 2

我建议您使用NSNofiticationCenter。

//in AppDelegate:
@interface AppDelegate()
{
    ...
    id lastViewController;
    ...
}

@implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    ...
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleCurrentViewController) name:@"CurrentViewController" object:nil];
    ...
}

- (void)handleCurrentViewController:(NSNotification *)notification {
    if([[notification userInfo] objectForKey:@"lastViewController"]) {
        lastViewController = [[notification userInfo] objectForKey:@"lastViewController"];
    }
}

- (void)applicationDidEnterBackground:(UIApplication *)application
{    
    NSLog(@"last view controller is %@", [(UIViewController *)lastViewController class]);
}
@end

//in every ViewController you want to detect
@implementation SomeViewController
...
- (void) viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];
    [[NSNotificationCenter defaultCenter] postNotificationName:@"CurrentViewController" object:nil userInfo:[NSDictionary dictionaryWithObjectsAndKeys:self, @"lastViewController", nil]];
}
...
@end

Answer 3

这对我有用。我有很多具有不同控制器的目标，所以以前的答案似乎没有用。

首先你要在AppDelegate类中使用它：

var window: UIWindow?

然后，在你的函数中

let navigationController = window?.rootViewController as? UINavigationController
if let activeController = navigationController!.visibleViewController {
    if activeController.isKindOfClass( MyViewController )  {
        println("I have found my controller!")    
   }
}

Answer 4

您可以尝试获取最顶层的视图：

[[[[UIApplication sharedApplication] keyWindow] subviews] lastObject];

虽然这个视图可能看不见甚至被其某些子视图覆盖......

这取决于您的用户界面，但它可能会有所帮助。

Answer 5

Swift的绝佳解决方案，在AppDelegate中实现

func getTopViewController()->UIViewController{
    return topViewControllerWithRootViewController(UIApplication.sharedApplication().keyWindow!.rootViewController!)
}
func topViewControllerWithRootViewController(rootViewController:UIViewController)->UIViewController{
    if rootViewController is UITabBarController{
        let tabBarController = rootViewController as! UITabBarController
        return topViewControllerWithRootViewController(tabBarController.selectedViewController!)
    }
    if rootViewController is UINavigationController{
        let navBarController = rootViewController as! UINavigationController
        return topViewControllerWithRootViewController(navBarController.visibleViewController)
    }
    if let presentedViewController = rootViewController.presentedViewController {
        return topViewControllerWithRootViewController(presentedViewController)
    }
    return rootViewController
}

目标 - C

- (UIViewController*)topViewController {
    return [self topViewControllerWithRootViewController:[UIApplication sharedApplication].keyWindow.rootViewController];
}

- (UIViewController*)topViewControllerWithRootViewController:(UIViewController*)rootViewController {
    if ([rootViewController isKindOfClass:[UITabBarController class]]) {
       UITabBarController* tabBarController = (UITabBarController*)rootViewController;
       return [self topViewControllerWithRootViewController:tabBarController.selectedViewController];
    } else if ([rootViewController isKindOfClass:[UINavigationController class]]) {
      UINavigationController* navigationController = (UINavigationController*)rootViewController;
      return [self topViewControllerWithRootViewController:navigationController.visibleViewController];
     } else if (rootViewController.presentedViewController) {
       UIViewController* presentedViewController = rootViewController.presentedViewController;
       return [self topViewControllerWithRootViewController:presentedViewController];
     } else {
       return rootViewController;
    }
}

Answer 6

如果App Delegate中有导航控制器，只需使用visibleViewController属性即可。它会为你提供可见的控制器，即使它是一个模态。

Answer 7

在swift中你可以得到这样的活动ViewController：

 let navigationController = application.windows[0].rootViewController as UINavigationController

 let activeViewCont = navigationController.visibleViewController

Answer 8

最佳解决方案也适用于moreNavigationController中的UITabBarController：

extension UIApplication {
    class func topViewController(base: UIViewController? = UIApplication.sharedApplication().keyWindow?.rootViewController) -> UIViewController? {

        if let nav = base as? UINavigationController {
            return topViewController(nav.visibleViewController)
        }

        if let tab = base as? UITabBarController {
            let moreNavigationController = tab.moreNavigationController

            if let top = moreNavigationController.topViewController  where top.view.window != nil {
                return topViewController(top)
            } else if let selected = tab.selectedViewController {
                return topViewController(selected)
            }
        }

        if let presented = base?.presentedViewController {
            return topViewController(presented)
        }

        return base
    }
}

Answer 9

下面的代码效果非常好。

+（UIViewController *）findBestViewController：（UIViewController *）vc {

if (vc.presentedViewController) {

    // Return presented view controller
    return [AppDelegate findBestViewController:vc.presentedViewController];

} else if ([vc isKindOfClass:[UISplitViewController class]]) {

    // Return right hand side
    UISplitViewController* svc = (UISplitViewController*) vc;
    if (svc.viewControllers.count > 0)
        return [AppDelegate findBestViewController:svc.viewControllers.lastObject];
    else
        return vc;

} else if ([vc isKindOfClass:[UINavigationController class]]) {

    // Return top view
    UINavigationController* svc = (UINavigationController*) vc;
    if (svc.viewControllers.count > 0)
        return [AppDelegate findBestViewController:svc.topViewController];
    else
        return vc;

} else if ([vc isKindOfClass:[UITabBarController class]]) {

    // Return visible view
    UITabBarController* svc = (UITabBarController*) vc;
    if (svc.viewControllers.count > 0)
        return [AppDelegate findBestViewController:svc.selectedViewController];
    else
        return vc;

} else {

    // Unknown view controller type, return last child view controller
    return vc;

}

}

+（UIViewController *）currentViewController {

// Find best view controller
UIViewController* viewController = [UIApplication sharedApplication].keyWindow.rootViewController;
return [AppDelegate findBestViewController:viewController];

}

Answer 10

上述其他解决方案仅部分工作，因为未处理复杂的视图层次结构（集成在标签栏控制器，拆分视图控制器，视图容器以及警报控制器中的导航控制器可能会搞乱）。

我通过保留当前视图控制器的引用来解决这个问题 AppDelegate中。每次视图出现时我都会利用 viewDidAppear(animated:)并在应用委托中设置引用。

我知道问题是关于Objective-C，但我只提供Swift代码，我相信它对两类用户都有用。

首先：我已经实施了一个协议来保持清洁和可重复使用：

protocol UpdatableViewController {
    func updateUI()
}

第二：我添加了对AppDelegate的引用：

var currentViewController: UpdatableViewController?

第三：我在viewDidAppear（）中设置当前视图控制器：

override func viewDidAppear(animated: Bool) {
    super.viewDidAppear(animated)
    let appDelegate = UIApplication.sharedApplication().delegate as? AppDelegate
    appDelegate?.currentViewController = self
}

第四：

extension ViewController1: UpdatableViewController {
    func updateUI() {
        print("Implement updating here")
    }
}

从app delegate获取当前视图控制器（可以使用模态）

10 个答案:

的UIViewController + TopMostViewController.h

的UIViewController + TopMostViewController.m