CODEWITHSUNDEEP
iosobjective-ciphoneuinavigationcontroller
doubleYou
doubleYou

Reputation: 310

UINavigationController keeps displaying popped view

So in an iOS app I'm using a UINavigationController as the root view controller. I then push a few ViewControllers on the stack, let's call them A, B, C and D.

Now if I try to pop D from the stack, I sometimes * run into the following problem: After calling popViewControllerAnimated, the view of the topmost view controller (D) remains. If I display the stack however, it is displayed correctly, i.e. A-B-C is displayed and D is gone. The pop method seems to do just what it's supposed to but the view does not reflect this.

I have tried various other approaches, (popToRootViewController, popToViewController) instead but the behaviour doesn't change (i.e. the stack is printed correctly but D's view remains). I have called setNeedsDisplay on all views that seem to make sense.

After popping D, I can still push and remove other view controllers. The stack reflects those changes, the view does not. Also, D's view remains responsive, i.e. it is not frozen and the app does behave correctly in the background. All views are very simple, there are no tabbed views or the like, just a couple of labels and buttons.

I have read a number of posts on SO and elsewhere about people having similar problems but none of the solutions seem to fit here. Does anyone have an idea why this happens?

*_ I haven't been able to figure out under which circumstances exactly. I first thought it was because I am popping D very soon after pushing it, but it also occasionally happens when there is more time between push and pop.

Upvotes: 0

Views: 91

Answers (2)

doubleYou
doubleYou

Reputation: 310

The problem seems to have been one of timing. As I mentioned, the push and pop operations (of D) sometimes do happen rather quickly after one another. Adding a delay of 2500 ms solved the problem. Adding 500 ms did not (always). Since neither is acceptable to me, I switched to a custom container view controller and therefore didn't spend a lot of time on figuring out what the minimum delay would be.

Just as sidenote: Changing from dispatch_async to dispatch_sync didn't have any effect. The delay seems to be necessary either way.

Thanks for everyone's help. I'm going to close this thread - if someone can provide a more complete answer as to why things are the way they are, please post it and I'll mark it as the correct answer then.

Upvotes: 0

Puran
Puran

Reputation: 994

Only reason i can think of where this might happen is if you are not doing that in a main thread. If you are doing it after some network call, then do make sure you are going back to main thread. Sometimes, app won't crash if you do UI work on background thread but rather will behave like what you are seeing!

Upvotes: 1

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