Present UIAlertController from AppDelegate

Question

I'm trying to present a UIAlertController from the AppDelegate in my iOS app. Below is the alert and the present method.

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

//Configure alert and actions

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

However, when I try to present the alert, it doesn't appear and I get the following alert in the console.

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

What is causing the error and how do I fix it?

Solution 1

You can use this code as well if you want to launch it from didFinishLaunchingWithOptions.Hope this helps.

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)
        })

And up-to-date:

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

Solution 2

try this code..

-(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]; 
}

Solution 3

It's better to use something like:

var hostVC = self.window?.rootViewController

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

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

Previous answers won't work if you are already presenting modal view controller.

Solution 4

you call it before the window is up and the navigationController is actually shown:

"Warning: Attempt to present on whose view is not in the window hierarchy!"

likely you do so in applicationDidFinishLaunching?

---

EITHER wait .. like do it when the view really appears

OR

one 'hack' would be to force the view and window up yourself:

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

Solution 5

I was trying the same but does not work because after change of viewcontroller still returned the initial viewcontroller and throw the error whose view is not in the window hierarchy!. Finally, I found the solution to this problem:

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

But I have to force view controllers to update de keyWindow with this:

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

View more solutions

Comments

[Zeb]

Hi @AdiQuadCore, your is useful only in swift application. In objC, the UIAlertController needs a pointer to the current UIViewController.

[Seoras]

This worked for me in ObjC in didFinishLaunchingWithOptions

[NerdyTherapist]

Perfect answer and a really good method to handle modally presented view controllers! Thanks!

[Colin Basnett]

UIAlertView is now deprecated.

[mfaani]

If you aren't not creating a new Window, do you still have to do makeKeyAndVisible? For window that comes with AppDelegate, doesn't that happen by default?!

[Daij-Djan]

In General: yes BUT It happens too late for the op's question

[mfaani]

I'm confused. what do you mean too late? Is your code correct or not?

[Daij-Djan]

Mine is correct for the given question :) makeKeyAndVisible is needed here

[Rafael Nobre]

You should not do that, really.

[meaning-matters]

How is the UIWindow deallocated?