iPhone UINavigation Issue - nested push animation can result in corrupted navigation bar

Question

I keep getting the following errors:

2011-04-02 14:55:23.350 AppName[42430:207] nested push animation can result in corrupted navigation bar
2011-04-02 14:55:23.352 AppName[42430:207] nested push animation can result in corrupted navigation bar
2011-04-02 14:55:23.729 AppName[42430:207] Finishing up a navigation transition in an unexpected state. Navigation Bar subview tree might get corrupted.
2011-04-02 14:55:23.729 AppName[42430:207] Finishing up a navigation transition in an unexpected state. Navigation Bar subview tree might get corrupted.

Here is what I am doing. From a view controller, I call the following when a certain button is pushed:

EventsViewController *viewController = [[EventsViewController alloc] init];
UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:viewController];
navController.navigationBar.tintColor = [UIColor blackColor];
[self presentModalViewController:navController animated:YES];
[viewController release];
[navController release];

Then, if a certain button is pushed in EventsController, I call:

SingleEventViewController *viewController = [[SingleEventViewController alloc] initWithEvent:[currentEvents objectAtIndex:indexPath.row]];
[self.navigationController pushViewController:viewController animated:YES];
[viewController release];

Then, if a certain button is pushed in SingleEventViewController, I call:

EventMapView* viewController = [[EventMapView alloc] initWithCoordinates];
[[self navigationController] pushViewController:viewController animated:YES];
[viewController release];

So yea, it's obvious that there's nested push animations, but isn't this the right way to go about it? I checked out Apple's DrillDownSave code and this appears to be how they're doing it. Does it matter that I use init methods instead of viewDidLoad methods?

Answer 1

Calling pushViewController before viewDidAppear is unsafe.

Answer 2

ACCIDENTLY TRIGGERING THE SAME SEGUE TWICE Once in code, and once from interface builder, but both at the same time...

I was getting the same error as the rest of you. Only my problem was I was accidentally firing the same segue, twice. Once from interface builder, and once from within my code.

I have a UITableView. When a cell is selected, a segue in interface builder fires. Heres my problem, I had the segue set up to be directly fired off clicking the CELL ITSELf, inside interface builder, then in my code, I had under didSelectRowAtIndexPath, code that would fire that same segue... like so...

[self performSegueWithIdentifier:@"MySegue" sender:tableView];

That means when didSelectRowAtIndexPath gets called because a row was selected, it fires the segue with the above line of code. Then interface builder, also triggers the segue, because its connected directly to the cell object in interface builder. To stop interface builder from directly firing the segue. You have to connect the segue from the top of the view controller, not nested down inside coming off of the cell itself.

So if you are having this problem for the same reason as me, that is, you are calling the same segue twice, you can fix this by unlinking the connection from the CELL DIRECTLY, to your segue, and having the segue connection originate at the top of the table hierarchy in IB, rather than nested inside the cell. Connect the segue from you View Controller itself, to the segue. If you have done this correct, when you select the segue, it should highlight the ENTIRE view it is coming from, not just the cell.

Now Apples documentation states thus under the performSegueWithIdentifier:sender: reference:

Apps normally do not need to trigger segues directly. Instead, you configure an object in Interface Builder associated with the view controller, such as a control embedded in its view hierarchy, to trigger the segue. However, you can call this method to trigger a segue programmatically, perhaps in response to some action that cannot be specified in the storyboard resource file. For example, you might call it from a custom action handler used to process shake or accelerometer events.

In my case, I have a search button for my UITableView, and whether the segue is called when the search results table is present, or the normal table view is present, had to be determined. So I needed to trigger the segue directly.

So remove the embedded control from interface builder, and just stick it on the view controller itself, then trigger the segue in your code!

Now, no more double segues! And no more errors.

Hope that helps, took me a good few hours to tackle this one.