self.navigationController.navigationBar setHidden:NO not working when view controllers are swapped out

Question

I'm experiencing some weird behavior with hiding and showing the UINavigationBar.

In my viewWillAppear method I'm calling this:

self.navigationController.navigationBar.hidden = YES;

and when the user presses a button I'm calling this:

self.navigationController.navigationBar.hidden = NO;

and then swapping out the current view controller using the viewControllers property of a custom UINavigationController.

This works fine, but if I try to show the navigationBar using the same line in the viewWillDisappear method, it doesn't work. The navigationBar is still hidden.

I'm able to show/hide the status bar in viewWillDisappear using the following method:

[[UIApplication sharedApplication] setStatusBarHidden:YES withAnimation:UIStatusBarAnimationFade];

but showing/hiding the UINavigationBar doesn't work!

EDIT: Also, self.navigationController.isNavigationBarHidden returns NO after I try to show the bar in viewWillDisappear but the bar is still hidden.

Any help would be greatly appreciated. Thank you!

Answer 1

Because you’ve already swapped the current view controller out of the stack, self.navigationController is probably nil when viewWillDisappear is called.

Answer 2

You're better off not messaging self.navigationController from viewWillDisappear as eager pointed out since it may be nil. Rather than holding on to a reference, I recommend editing the navigationBarHidden property always from within viewWillAppear as in this answer https://stackoverflow.com/a/27748007/2248638 . I have a BOOL navigationBarHidden property on my UIViewController base class so that I only need to set the property once for those view controllers which are hidden.

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    [self.navigationController setNavigationBarHidden:self.navigationBarHidden animated:animated];
}