Question

I’m getting strange navigation bar behaviour, for example when I hit back button the screen displayed is the previous screen, however the Navigation Bar items do change. So I’m left with screen A, but with nav bar buttons for screen B.

Could this be due to memory leaks? I do note with my app still:

1. This behavior seems to happen:

   • immediately if I trigger memory
     warning via the simulator menu, or
   • on a device after it has been on
     for a while [without being killed
     and then restarted as an app].

2. I do have some memory leaks I’m
   trying to clean up (i.e. Profiler
   highlights items in “leaked blocks”
   section)

Any tips on fault finding root cause of why pushing a back button would end up in a weird state? e.g. screen on previous parent view, but nav bar items don’t change…

UPDATE – I have finally removed the memory leaks in my app, however I note the nav bar issue still remains. I guess this doesn’t confirm the answer to my question is NO in general, but in my specific case it wasn’t the memork leak…

Answer 1

From Apple:

The navigation controller updates the
navigation bar each time the top view
controller changes. Thus, these
changes occur each time a view
controller is pushed onto the stack or
popped from it. When you animate a
push or pop operation, the navigation
controller similarly animates the
change in navigation bar content.

Based on this, I would start by looking for a bug or misconfiguration in your view definitions. Check for any InterfaceBuilder warnings if you defined your views via NIBs. Make sure your view hierarchies are correct in both UIViewControllers. Also check for possible bugs in your view life-cycle methods: viewWillAppear:, viewWillDisappear:, etc,.

Actually, it would be nice if you could post some screenshots and/or code. Thanks!