How come some of my UIViews are shifted after navigation?

Question

In some of my application designs or for just some UIViews, following a navigationController's pushViewController, my new view will be shifted off the window by the height of the status bar. As a result, I will put this code stub in the viewDidLoad method.

CGRect  frameAt = [self.view frame];
CGRect  statusBarFrame = [[UIApplication sharedApplication] statusBarFrame];
frameAt.origin.y += statusBarFrame.size.height;
[self.view setFrame: frameAt];

It does not make sense to me that this is the intention of XCode and Interface Builder, so I suspect that I am doing something fundamentally wrong with the SDK during my view design. Furthermore, on the rare occasion that I don't have to shift my view, I really don't know what the difference in the two design approaches.

Note also, that most of the time I try to design my views using IB, with some minor customization.

Does anyone else run into this and know what they do to fix without such a code stub?

Answer 1

I've used Apple's NavBar sample code to try and reproduce this problem.

the applicationDidFinishLaunching is originally implemented like this:

[window addSubview:navigationController.view];
[window makeKeyAndVisible];

If I change it to this:

UIViewController *shellController = [[UIViewController alloc] initWithNibName:nil bundle:nil];
[shellController.view addSubview:navigationController.view];
[window addSubview:shellController.view];
[window makeKeyAndVisible];

Then I get the gap appearing.

However if I only do this:

UIView *shell = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
[shell addSubview:navigationController.view];
[window addSubview:shell];
[window makeKeyAndVisible];

Then everything looks normal.

So I guess every view controller will offset its view if its the root view controller. But the navigation controller overrides this behaviour to offset its view regardless of whether it's the root view controller. Therefore I would say your gap is appearing because you've got a navigation controller somewhere lower in the hierarchy than it's supposed to be.