从 AppDelegate 呈现 UIAlertController [重复]

Question

我正在尝试在我的 iOS 应用程序中从 AppDelegate 提供UIAlertController。 下面是警报和当前方法。

UIAlertController *alert = [UIAlertController alertControllerWithTitle:cTitle message:cMessage preferredStyle:UIAlertControllerStyleAlert];

//Configure alert and actions

[self.window.rootViewController presentViewController:alert animated:TRUE completion:nil];

但是，当我尝试显示警报时，它没有出现，并且我在控制台中收到以下警报。

Warning: Attempt to present <UIAlertController: 0x145f5d60> on <UINavigationController: 0x146590f0> whose view is not in the window hierarchy!

是什么导致了错误，我该如何解决？

Answer 1

如果您想从 didFinishLaunchingWithOptions 启动它，也可以使用此代码。希望这会有所帮助。

dispatch_async(dispatch_get_main_queue(), {
              let importantAlert: UIAlertController = UIAlertController(title: "Action Sheet", message: "Hello I was presented from appdelegate ;)", preferredStyle: .ActionSheet)
            self.window?.rootViewController?.presentViewController(importantAlert, animated: true, completion: nil)
        })

并且是最新的：

DispatchQueue.main.async {
    let alert = UIAlertController(title: "Hello!", message: "Greetings from AppDelegate.", preferredStyle: .alert)
    self.window?.rootViewController?.present(alert, animated: true, completion: nil)
}

Answer 2

试试这个代码..

-(void)application:(UIApplication *)application               didReceiveLocalNotification:(UILocalNotification *)notification
{
 NSLog(@"rakshapettu");
 UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"AlertView" message:@"I am an AlertView" preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction* defaultAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault
                                                      handler:^(UIAlertAction * action) {
                                                          [alert dismissViewControllerAnimated:YES completion:nil];
                                                      }];
[alert addAction:defaultAction];
UIWindow *alertWindow = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
alertWindow.rootViewController = [[UIViewController alloc] init];
alertWindow.windowLevel = UIWindowLevelAlert + 1;
[alertWindow makeKeyAndVisible];
[alertWindow.rootViewController presentViewController:alert animated:YES completion:nil]; 
}

Answer 3

最好使用类似的东西：

var hostVC = self.window?.rootViewController

while let next = hostVC?.presentedViewController {
    hostVC = next
}

hostVC?.presentViewController(alertController, animated: true, completion: nil)

如果您已经在展示模态视图控制器，则以前的答案将不起作用。

Answer 4

你在窗口打开之前调用它，navigationController 实际显示出来：

“警告：试图展示不在窗口层次结构中的视图！”

您可能会在 applicationDidFinishLaunching 中这样做吗？

---

等一下 .. 喜欢在视图真正出现时这样做

或

一个“黑客”是强制视图和窗口自己打开：

[self.window addSubview:self.rootViewController.view];
[self.window makeKeyAndVisible];

Answer 5

我尝试了同样的方法，但不起作用，因为在更改视图控制器后仍然返回初始视图控制器并抛出错误 whose view is not in the window hierarchy!。终于找到了解决这个问题的办法：

UIApplication.sharedApplication().keyWindow?.rootViewController?.presentViewController(alertController, animated: true, completion: nil)

但我必须强制视图控制器更新 de keyWindow：

override func viewDidAppear(animated: Bool) {
    super.viewDidAppear(animated)
    UIApplication.sharedApplication().keyWindow!.rootViewController = self
    UIApplication.sharedApplication().keyWindow!.makeKeyAndVisible()
}

Answer 6

您可以尝试使用viewDidAppear 而不是viewDidLoad 调用它。我有一个类似的错误并修复了它。

Answer 7

使用警报控制器：

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
dispatch_async(dispatch_get_main_queue(), {

    //INTERNET NOT AVAILABLE ALERT
    var internetUnavailableAlertController = UIAlertController (title: "Network Unavailable", message: "Please check your internet connection settings and turn on Network Connection", preferredStyle: .Alert)

    var settingsAction = UIAlertAction(title: "Settings", style: .Default) { (_) -> Void in
        let settingsUrl = NSURL(string: UIApplicationOpenSettingsURLString)
        if let url = settingsUrl {
            UIApplication.sharedApplication().openURL(url)
        }
    }
    var cancelAction = UIAlertAction(title: "Okay", style: .Default, handler: nil)
    internetUnavailableAlertController .addAction(settingsAction)
    internetUnavailableAlertController .addAction(cancelAction)
    self.window?.rootViewController!.presentViewController(internetUnavailableAlertController , animated: true, completion: nil)
    })

使用警报视图：

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {

    dispatch_async(dispatch_get_main_queue(), {

        //INTERNET NOT AVAILABLE ALERTVIEW

        let internetUnavailableAlert =  UIAlertView(title: "Network Unavailable", message: "Please check your internet connection settings and turn on Network Connection", delegate: self, cancelButtonTitle: "Okay")
        internetUnavailableAlert.show()
        })

  return true
 }
}