https://github.com/jpsim/uicollectionview-animation-bug

There's a confirmed bug in UICollectionView. This project highlights a workaround.
https://github.com/jpsim/uicollectionview-animation-bug

Last synced: 10 days ago
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There's a confirmed bug in UICollectionView. This project highlights a workaround.

• Host: GitHub
• URL: https://github.com/jpsim/uicollectionview-animation-bug
• Owner: jpsim
• Created: 2013-06-15T01:48:14.000Z (over 11 years ago)
• Default Branch: master
• Last Pushed: 2013-06-26T04:54:04.000Z (over 11 years ago)
• Last Synced: 2025-01-09T02:29:40.366Z (15 days ago)
• Language: Objective-C
• Size: 363 KB
• Stars: 33
• Watchers: 3
• Forks: 2
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Collection View Animation Bug Sample Code

## The bug

There's a bug (confirmed by Apple) in the otherwise excellent `UICollectionView`'s `performBatchUpdates` method which causes cells that are initially off-screen animating on-screen to just appear at their final location instead of animating there. This is better understood visually:

![Video of bug](UICV_Animation_Bug.gif)

Notice how the last cell doesn't animate when reappearing? This is a simple demo, but there are cases in which the bug is drastically more jarring.

## The demo project

This demo project is the result of having tried tons of work-arounds to get this animation to work, when finally the best solution was the crudest.

## The fix

The solution is really more of a hack: make the collection view bigger during the animation so that it can accurately animate the appearing cells.

Essentially:

``` objc

frameUpdate.size.height += kExpandedHeight - kCollapsedHeight;

collectionView.frame = frameUpdate;

[collectionView performBatchUpdates:^{

	_cells[indexPath.item] = @(newHeight);

} completion:^(BOOL finished) {

    frameUpdate.size.height -= kExpandedHeight - kCollapsedHeight;

    collectionView.frame = frameUpdate;

}];

```

## License

Feels weird to license something so small, but this demo is MIT licensed.