no UICollectionViewLayoutAttributes instance for -layoutAttributesForSupplementaryElementOfKind:

Question

The title is the error I\'m getting and I have no idea why, but here is some information so hopefully someone on here can elucidate me.

I have subclassed UICol

Answer 1

I scoured the forums looking for an answer and came across a few suggestions. None of them gave me the succour I needed, and eventually in the interest of meeting deadlines, I dropped the use of supplementary views altogether.

A few weeks later out of curiosity I looked around again and eventually came across the following post and now I'm back to using supplementary views again.

So, don't forget to return your:

- (NSArray<NSIndexPath *> *)indexPathsToDeleteForSupplementaryViewOfKind:(NSString *)elementKind
{
    return self.removedIndexPaths;
}

to your collection view layout.

Answer 2

To prevent a crash you could return dummy attributes for all those indexPaths that are not valid any more. Something like this could help to prevent your crash:

UICollectionViewLayoutAttributes *layoutAttributes = self.layoutInfo[elementKind][indexPath]; // add some safety checks if this access creates an out of bounds issue

// create dummy layoutAttributes
// the workaround
if (layoutAttributes == nil) {
    UICollectionViewLayoutAttributes *dummyLayoutAttributes = [UICollectionViewLayoutAttributes layoutAttributesForSupplementaryViewOfKind:elementKind withIndexPath:indexPath];
    dummyLayoutAttributes.frame = CGRectZero;
    dummyLayoutAttributes.hidden = YES;
    layoutAttributes = dummyLayoutAttributes;
}

return layoutAttributes;

This still leads to objects in your view stack that should not be there, but they are hidden and don't create a crash. The next time the UICollectionView updates it's layout it should clean out the old hidden views.