how to get my UIWindow using UIApplication?

Question

I have only one window and I tried

UIWindow* mWindow = [[UIApplication sharedApplication] keyWindow];

but this returned nil.

I also tried:

UIWindow* mWindow = (UIWindow*)[[UIApplication sharedApplication].windows objectAtIndex:0];

But this raised an exception and the app closed, when I tried to print out

[[UIApplication sharedApplication].windows count]

It printed 0

Note: I am putting this in my only view controller's viewDidLoad method and this is completely a new iPad View Based Application so I changed nothing, just trying to get the window

Please help me to get this object

score 49 · Accepted Answer · answered Sep 23 '10 at 20:41

49

If your main window is an outlet of your AppDelegate (which should be the case), you may simply use

MyAppDelegate* myDelegate = (((MyAppDelegate*) [UIApplication sharedApplication].delegate));
[myDelegate.window ...]

answered Sep 23 '10 at 20:41

Philipp Schlösser

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score 42 · Answer 2 · answered Mar 25 '13 at 19:25

42

Easiest way is to get the window from the app delegate instead:

UIWindow *keyWindow = [[[UIApplication sharedApplication] delegate] window];
// Do something with the window now

answered Mar 25 '13 at 19:25

iwasrobbed

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cduhn · Answer 3 · 2010-09-23T21:00:00.420

20

Your application's key window isn't set until [window makeKeyAndVisible] gets called in your app delegate. Your UIViewController is probably being loaded from a NIB before this call. This explains why keyWindow is returning nil.

Luckily, your view controller doesn't need to go through UIApplication to get the window. You can just do:

UIWindow *mWindow = self.view.window;

edited Sep 23 '10 at 21:00

answered Sep 23 '10 at 20:51

cduhn

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6

That's because the view isn't part of the view hierarchy yet. The same is true in viewWillAppear:. – tomwhipple Nov 09 '11 at 00:05

score 7 · Answer 4 · answered Aug 04 '11 at 00:21

7

[[[UIApplication sharedApplication] windows] objectAtIndex:0]; // You can also check the count of this to make sure, because if there are no windows it will crash.

answered Aug 04 '11 at 00:21

BadPirate

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score 0 · Answer 5 · answered Apr 27 '22 at 20:26

0

With iOS 13+ you should use:

if let currentScene = UIApplication.shared.connectedScenes.first as? UIWindowScene,
    let window = currentScene.keyWindow {
    // now window contains the active window
}

answered Apr 27 '22 at 20:26

Alexander Jährling

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score 0 · Answer 6 · answered Jan 20 '23 at 12:03

You can achieve this in multiple ways. I like to use one of the following.

Use this when you need to access it just once.

if let window = UIApplication.shared.windows.first as UIWindow? {
    // Action
}

If you need to access the UIWindow multiple times, I would suggest extending a class. I like to extend the UIViewController.

extension UIViewController {
    /// Returns the UIWindow if available.
    public var window: UIWindow? {
        UIApplication.shared.windows.first as UIWindow?
    }
}

how to get my UIWindow using UIApplication?

6 Answers6

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