UINavigationBar jumps 20pixels during transitionFromViewController - animation

Question

In trying to attempt to use Apple's UIViewController containment I have encountered a problem with animating the transition between two UIViewControllers.
Here is the set up... I have created a UITabBarController and within one of the tabs I have created a UIViewController as a container. This ViewController manages the transition between a UIViewController and a UINavigationController. The before view is:
When the Next button is tapped the view begins it's transition with a flipFromRight transition. During the transition, the Navigation bar is in "to" view but is located 20pixels down from the top edge of the view. Picture below:
The green is the background color of the container view. Once the new view completes the transition, the Navigation bar snaps up to the top of the view and the final result is:
The time to snap in place is independent of the duration of the animation. I achieve the final state that I want, but the transition is a problem.
I have instrumented the viewController lifecycle and the frames of the Navigation bar and the UITableView are as specified in the XIB. The xib looks like this:
Here is the code:
In -viewDidLoad -
_fromVC = [[FromVC alloc] initWithNibName:#"FromVC" bundle:nil delegate:self];
[self addChildViewController:_fromVC];
[self.view addSubview:_fromVC.view];
[_fromVC didMoveToParentViewController:self];
In my button handler -
- (void)buttonSelected
{
//
// Create the "to" View controller
//
ToVC *toVC = [[ToVC alloc] initWithNibName:#"ToVC" bundle:nil];
//
// Create the navigation controller for the study activity
//
_toNavCon = [[UINavigationController alloc] initWithRootViewController:toVC];
[self addChildViewController:_toNavCon];
[_fromVC willMoveToParentViewController:nil];
[self transitionFromViewController:_fromVC
toViewController:_toNavCon
duration:0.7
options:UIViewAnimationOptionTransitionFlipFromRight
animations:nil
completion:^(BOOL finished) {
[_fromVC removeFromParentViewController];
[_toNavCon didMoveToParentViewController:self];
}];
}
There is no code in "to" view controller that changes the appearance of the view controller.
Another bit of information... When I "toggle In-Call status bar" in the simulator the gap at the top of the navigation bar is the height of the In-Call status bar.
I have looked at everything on the web and there is nothing that helps. Has anyone seen this and has anyone fixed it?

Answer 1

I did find an answer!! Subclass UINavigationController and override
- (BOOL)wantsFullScreenLayout{
return NO;
}
Apparently, UINavigationController and UITabController always want the full screen (default YES) - adjusting for the status bar - and you can not set this property any other way. It has been working for me.