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objective-ccocoa-touchuikituiwindow

Advantages, problems, examples of adding another UIWindow to an iOS app?

Recently I've been wondering about the fact that that an iOS app only has one UIWindow. It does not seem to be an issue to create another UIWindow and place it on screen.

My question is kind of vague, but I'm interested in:

  • What could I potentially achieve with a second UIWindow that cannot be done in other ways?
  • What can go wrong when using multiple UIWindow instances?
  • I have seen that people use a 2nd UIWindow to display popover like views on iPhone. Is this a good way of doing it? Why? Why not?
  • Are there other examples where it is making perfectly sense to have another UIWindow?

It's not that I'm missing something. I have never felt the need to create another UIWindow instance but maybe it would allow doing amazing things I'm not aware of! :-)

I'm hoping that it might help me solve this problem: I need to add a "cover view" over whatever is currently displayed. It should also work if there are already one or more modal controllers presented. If I add a UIView to the root controller's view, the modal controllers sit on top, so do the popover controllers. If I present the cover view modally and there is already a modal controller, only part of the screen is covered.

Solution

  • A UIWindow can float above other UI elements like the system keyboard.

    To address your last paragraph: Make a UIWindow with the same frame as your main window. Set its windowLevel property to UIWindowLevelStatusBar. Set its hidden property to NO.