UICollectionView: Assertion failure in -[UICollectionView _endItemAnimations]

Question

I'm getting this error in my app:

*** Assertion failure in -[UICollectionView _endItemAnimations], /SourceCache/UIKit/UIKit-2372/UICollectionView.m:2801

It happens in my -controllerDidChangeContent: method on this line:

[self.collectionView performBatchUpdates:^{...}];

Does anyone know what causes this? My code is closely based off of https://gist.github.com/4440c1cba83318e276bb and I'm at a loss.

Thanks!

score 9 · Answer 1 · answered May 09 '13 at 15:16

9

These types of assertions get thrown as exceptions. Wrap the batch updates in a try/catch and dump the exception description. It will tell you exactly what it doesn't like about your call.

In other words:

    @try
    {
        [self.collectionView performBatchUpdates:^{...}];
    }
    @catch (NSException *except)
    {
        NSLog(@"DEBUG: failure to batch update.  %@", except.description);
    }

answered May 09 '13 at 15:16

FranG

91
1
2

Good option for debugging. – kelin Jul 15 '15 at 13:44

score 1 · Answer 2 · answered Dec 07 '12 at 20:08

1

I bet it's because of that your

-controllerDidChangeContent

is being called in background thread multiple times, and performBatchUpdates is still working when another thread calls it, so it leads to incorrect behavior.

Solution - try to wrap it in @synchronized or using NSLocks

answered Dec 07 '12 at 20:08

Bogdan Andresyuk

523
2
6

It was definitely being called on the main thread so this wasn't the issue – Dec 08 '12 at 00:32

score 1 · Answer 3 · answered Dec 08 '12 at 00:32

1

The issue was not setting the FRC delegate to nil on view didDisappear.

answered Dec 08 '12 at 00:32

Cheers! That was it! Setting FRC to nil on viewDidDisappear and reassigning to self of viewWillAppear solved my similar issue. – So Over It Jul 13 '13 at 07:06
What does FRC stand for? :-| – Kalle Aug 04 '13 at 12:03
@Kalle: FRC = Fetched Results Controller – AlexR Oct 25 '13 at 12:35

UICollectionView: Assertion failure in -[UICollectionView _endItemAnimations]

3 Answers3