how can I animate the UINavigationBar background change on UIViewController push?

Question

My app uses two different backgrounds for the UINavigationBar to indicate to the user what level in the hierarchy they're at. When I push a UIViewController that needs the second background it lacks animation, the background changes immediately as soon as the UIViewController is pushed. How can I animate this so that the background change fades as the view is being changed?

Answer 1

I know this is an old thread, but this worked for me:

CATransition *transition = [CATransition animation];
transition.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
transition.type = kCATransitionFade;
transition.duration = 0.5;

[self.navigationController.navigationBar.layer addAnimation:transition forKey:nil];
[self.navigationController.navigationBar setBackgroundImage:[[UIImage imageNamed:@"navigationbar.png"]resizableImageWithCapInsets:UIEdgeInsetsMake(44, 20, 44, 20)] forBarMetrics:UIBarMetricsDefault];        

Place this inside your viewDidLoad method. You'll need to link/import the QuartzCore framework.