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I subclassed UICollectionViewLayout. So far, so good.
However, I have some cells that are wider than the screen, and sometimes these disappear while scrolling. When you scroll some more, they magically reappear where they should be. I can show you my code, however I think there's nothing wrong with it since it works in 90% of the cases.. However, really large cells (more than two times the screen size) disappear sometimes. 

NSMutableArray* attributes = [NSMutableArray array];
for (int section=0; section < [[self collectionView] numberOfSections]; section++) {
    [attributes addObject:[self layoutAttributesForSupplementaryViewOfKind:UICollectionElementKindSectionHeader atIndexPath:[NSIndexPath indexPathForItem:0 inSection:section]]];
        for (int row=0; row < [[self collectionView] numberOfItemsInSection:section]; row++) {
            NSIndexPath* indexPath = [NSIndexPath indexPathForItem:row inSection:section];
            [attributes addObject:[self layoutAttributesForItemAtIndexPath:indexPath]];
        }
 }
 return attributes;

I've also these posts: UICollectionView's cell disappearing and Large cells in a UICollectionView getting removed while the cell is still displayed However, a solution isn't mentioned. Can anybody help me with this? Could it be the problem is on Apple's side? And if it is, is there anything I can do to solve it myself?

Community
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s1m0n
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2 Answers2

5

Sorry to tell you: I'm pretty sure this a real bug in UICollectionView; I've run into this exact same thing a few weeks ago. I've made a small program to demonstrate the bug and filed a RADAR with Apple, but haven't heard back on whether or if they plan on fixing it. The best workaround I can think of (Warning: I haven't yet implemented this workaround) is to notice that the layout attributes are very far off the edges of the screen, intentionally change the bounds of the cell attributes so it only slightly goes off screen, and possibly store that offset (the amount that you trimmed off of what the real bounds should be) as an additional custom field in the layoutAttributes, so your cell knows to draw it's content correctly. Which feels like a gross hack, but it ought to work.

Tim Gogolin
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Are you sure you return the right attribute object for this cell when method -(NSArray*)layoutAttributesForElementsInRect:(CGRect)rect is called and when the rect is just a part of your cell ?

CitronEvanescent
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  • Users also report having issues with very large cells. See : http://stackoverflow.com/questions/13016302/large-cells-in-a-uicollectionview-getting-removed-while-the-cell-is-still-displa?rq=1 – CitronEvanescent Dec 20 '12 at 13:37