iOS5 breaks UISplitViewController rotation callbacks, how to invoke manually?

Question

As has been reported in other questions here on SO, iOS 5 changes how rotation callbacks for split view controllers are sent as per this release note. This is not a dupe (I think), as I can't find another question on SO that deals with how to adjust split view controller usage in iOS 5 to cope with the change:

Rotation callbacks in iOS 5 are not applied to view controllers that are presented over a full screen. What this means is that if your code presents a view controller over another view controller, and then the user subsequently rotates the device to a different orientation, upon dismissal, the underlying controller (i.e. presenting controller) will not receive any rotation callbacks. Note however that the presenting controller will receive a viewWillLayoutSubviews call when it is redisplayed, and the interfaceOrientation property can be queried from this method and used to lay out the controller correctly.

I'm having trouble configuring the popover button in my root split view controller (the one that is supposed to show the left pane view in a popover when you're in portrait). Here's how my app startup sequence used to work in iOS 4.x when the device is in landscape mode:

1. Install split view controller into window with [window addSubview:splitViewController.view]; [window makeKeyAndVisible];. This results in splitViewController:willHideViewController:withBarButtonItem:forPopoverController: being called on the delegate (i.e. simulating a landscape -> portrait rotation) even though the device is already in landscape mode.

2. Present a fullscreen modal (my loading screen) which completely covers the split view underneath.

3. Finish loading and dismiss the loading screen modal. Since the device is in landscape mode, as the split view controller is revealed, this causes splitViewController:willShowViewController:invalidatingBarButtonItem: to be called on the delegate (i.e. simulating a portrait -> landscape rotation), thereby invalidating the bar button item, removing it from the right-side of the split view, and leaving us where we want to be. Hooray!

So, the problem is that because of the change described in that release note, whatever happens internally in iOS 4.3 that results in splitViewController:willShowViewController:invalidatingBarButtonItem: being called no longer happens in iOS 5. I tried subclassing UISplitViewController so I could provide a custom implementation of viewWillLayoutSubviews as suggested by the release note, but I don't know how to reproduce the desired sequence of internal events that iOS 4 triggers. I tried this:

- (void) viewWillLayoutSubviews
{
    [super viewWillLayoutSubviews];

    UINavigationController *rightStack = [[self viewControllers] objectAtIndex:1];
    UIViewController *rightRoot = [[rightStack viewControllers] objectAtIndex:0];
    BOOL rightRootHasButton = ... // determine if bar button item for portrait mode is there

    // iOS 4 never goes inside this 'if' branch
    if (UIInterfaceOrientationIsLandscape( [self interfaceOrientation] ) &&
        rightRootHasButton)
    {
        // Manually invoke the delegate method to hide the popover bar button item
        [self.delegate splitViewController:self
                    willShowViewController:[[self viewControllers] objectAtIndex:0]
                 invalidatingBarButtonItem:rightRoot.navigationItem.leftBarButtonItem];
    }
}

This mostly works, but not 100%. The problem is that invoking the delegate method yourself doesn't actually invalidate the bar button item, so the first time you rotate to portrait, the system thinks the bar button item is still installed properly and doesn't try to reinstall it. It's only after you rotate again to landscape and then back to portrait has the system got back into the right state and will actually install the popover bar button item in portrait mode.

Based on this question, I also tried invoking all the rotation callbacks manually instead of firing the delegate method, e.g.:

// iOS 4 never goes inside this 'if' branch
if (UIInterfaceOrientationIsLandscape( [self interfaceOrientation] ) &&
    rightRootHasButton)
{
    [self willRotateToInterfaceOrientation:self.interfaceOrientation duration:0];
    [self willAnimateRotationToInterfaceOrientation:self.interfaceOrientation duration:0];
    [self didRotateFromInterfaceOrientation:self.interfaceOrientation];
}

However this just seems to cause an infinite loop back into viewWillLayoutSubviews :(

Does anyone know what the correct way to simulate the iOS4-style rotation events is for a split view controller that appears from behind a full-screen modal? Or should you not simulate them at all and is there another best-practices approach that has become the standard for iOS5?

Any help really appreciated as this issue is holding us up from submitting our iOS5 bugfix release to the App Store.

Answer 1

I don't know the right way to handle this situation. However, the following seems to be working for me in iOS 5.

1. In splitViewController:willHideViewController:withBarButtonItem:forPopoverController:, store a reference to the barButtonItem in something like self.barButtonItem. Move the code for showing the button into a separate method, say ShowRootPopoverButtonItem.

2. In splitViewController:willShowViewController:invalidatingBarButtonItem:, clear that self.barButtonItem reference out. Move the code for showing the button into a separate method, say InvalidateRootPopoverButtonItem.

3. In viewWillLayoutSubviews, manually show or hide the button, depending on the interface orientation

Here's my implementation of viewWillLayoutSubviews. Note that calling self.interfaceOrientation always returned portrait, hence my use of statusBarOrientation.

- (void)viewWillLayoutSubviews
{
   if (UIInterfaceOrientationIsPortrait(
       [UIApplication sharedApplication].statusBarOrientation))
   {
      [self ShowRootPopoverButtonItem:self.barButtonItem];
   }
   else
   {
      [self InvalidateRootPopoverButtonItem:self.barButtonItem];
   }
}