问题
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
回答1:
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 ...]
回答2:
Easiest way is to get the window from the app delegate instead:
UIWindow *keyWindow = [[[UIApplication sharedApplication] delegate] window];
// Do something with the window now
回答3:
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;
回答4:
[[[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.
来源：https://stackoverflow.com/questions/3782066/how-to-get-my-uiwindow-using-uiapplication