Presenting a view controller triggers UIApplicationDidChangeStatusBarOrientationNotification - ios

Question

I've got a universal app that supports both iPad and iPhone, and on the iPhone it supports UIInterfaceOrientationPortraitUpsideDown.
When I run the app on an iPhone, then rotate the device to UIInterfaceOrientationPortraitUpsideDown, then modally present a view controller like this:
UIViewController* vc = [[UIViewController alloc] initWithNibName:nil bundle:nil];
UINavigationController* navigationController = [[UINavigationController alloc]
initWithRootViewController:vc];
navigationController.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
[self presentViewController:navigationController animated:YES completion:nil];
Very unexpectedly, this triggers UIApplicationDidChangeStatusBarOrientationNotification.
OK, so maybe this is because the modal view controller does not support the upside-down portrait orientation. Let's make a custom subclass of UIViewController that overrides supportedInterfaceOrientations:
- (NSUInteger) supportedInterfaceOrientations
{
return UIInterfaceOrientationMaskAll;
}
But no difference, presenting the custom VC still triggers the notification. I also noticed that the notifications is not triggered on iPad, only on iPhone. Finally, the behaviour is the same in iOS 8 and iOS 7 (specifically I am testing on iOS 8.1 and iOS 7.1, but I doubt that this makes any difference).
Question: Is it normal that this notification is sent when a modal VC is presented? Why does it happen only for UIInterfaceOrientationPortraitUpsideDown, but not for the regular portrait or any of the two landscape orientations? And why does it happen only on iPhone, not on iPad?
Note: I can provide a more complete, minimal running example on request.

Answer 1

The problem was, indeed, that the modally presented view controller did not support UIInterfaceOrientationPortraitUpsideDown. My idea to add an override of supportedInterfaceOrientations was correct, but where I went wrong was that I added the override to the custom subclass of UIViewController - but this is not the presented view controller!
The presented view controller, as my code snippet shows, is the UINavigationController instance. One correct solution to my problem therefore is to create a subclass of UINavigationController and add supportedInterfaceOrientations to that subclass.
Another correct, but in my case more elegant solution than subclassing is to make use of the UINavigationControllerDelegate protocol.
Step 1: Modify the code snippet from my question:
UIViewController* vc = [[UIViewController alloc] initWithNibName:nil bundle:nil];
UINavigationController* navigationController = [[UINavigationController alloc]
initWithRootViewController:vc];
navigationController.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
// --- THE NEXT LINE IS NEW ---
navigationController.delegate = self;
[self presentViewController:navigationController animated:YES completion:nil];
Step 2: Make sure that the class that contains the presenting code (= the above code snippet) adopts the UINavigationControllerDelegate protocol.
Step 3 (yes, there is a step 3): Add this protocol method to the newly designated delegate class:
- (NSUInteger) navigationControllerSupportedInterfaceOrientations:(UINavigationController*)navigationController
{
return UIInterfaceOrientationMaskAll;
}
If you have many places where you present view controllers you will probably want to have some shared object that adopts UINavigationControllerDelegate, but that's part of your application design.