RootViewController animation transition, initial orientation is wrong

Question

So I followed this thread: RootViewController Switch Transition Animation to transit the window.rootViewController from A to B to C. Code looks like this:

[UIView transitionWithView:self.window 
                  duration:0.5 
                   options: UIViewAnimationOptionTransitionFlipFromLeft 
                animations:^{
                               self.window.rootViewController = newViewController;
                } 
                completion:nil];

The problem is my app shall only support landscape, but during the rootViewController transition, the new view controller appears in portrait mode than quickly rotate to landscape mode.

I'm sure that:

1. I've set UISupportedOrientation to landscape (home button right)
2. for each viewcontroller, in the shouldAutoRotateToOrientation method, I set only for landscape

What could be the other reason?

Answer 1

I looked into this just now because I kept getting the same issue. I randomly tried the following, and it worked perfectly:

[UIView
    transitionWithView:window 
    duration:0.5
    options:UIViewAnimationOptionTransitionCrossDissolve
    animations:^(void) {
        BOOL oldState = [UIView areAnimationsEnabled];
        [UIView setAnimationsEnabled:NO];
        [(ICApp *)sharedApplication.delegate window].rootViewController = self;
        [UIView setAnimationsEnabled:oldState];
    } 
    completion:nil];

I know it's a bit odd to disable/enable animations inside an animation block, but the cross dissolve animates, and the rotation does not -- the view controller appears already rotated and ready to roll.