Handling Orientation with Multiple Windows on iPad

Question

I have a iPad application which goes between two states, one using a SplitView the other a TableView.

Currently I have a single UIWindow object, and switch between views with the following code

-(void) switchToStateA {
[viewControllerB.view removeFromSuperview];
[window addSubview:viewControllerA.view];
}
-(void) switchToStateB {
[viewControllerA.view removeFromSuperview];
[window viewControllerB.view];
}

Everything works fine unless I change the device orientation. After changing orientation and switching states, the state which was not active during the change is still in the frame of its old state (leaving black areas at the edge of the display). If I change the orientation again the new state will be fixed.

I've tried adding

[viewControllerA.view setNeedsLayout];

after swapping the views but it did not have an effect.

How do I make sure the background view controllers get the orientation callback, or how do I invoke a 'refresh' when I switch state?

Answer 1

This is pure speculation on my part, but what if instead of removing the view controller's view from the window, you set the view to hidden and use exchangeSubviewAtIndex:withSubviewAtIndex: to change which view controller's view is visible to the user. I wonder if the OS is optimizing not sending rotation events to any view controllers whose views don't have a super view.

You could even get fancy with animations and fade the top view's alpha to 0 while the bottom view's alpha fades to 1 before they switch places.

Answer 2

Device orientation changes are handled by UIViewControllers, not by isolated UIViews. The easiest way to solve your problem is to make the controller's view a dumb container, which you never remove from the window. The container view will always be correctly rotated as permitted by the controller. Then you just add/remove subviews to/from the container view to get them rotated too. Don't forget to set subviews' frames and autoresizing masks before adding them to the container view.