UICollectionView reloadSections with animation

Question

I'd like to reload UICollectionView with some interesting animation. In UITableView there's a method called reloadSections:withRowAnimation. But in UICollectionView there's just reloadSections.

How can I customize reloadSections animation? I definitely saw this in apps on the App Store.

possible duplicate of [UICollectionView animate data change](http://stackoverflow.com/questions/13272315/uicollectionview-animate-data-change) — Vinzzz, Oct 09 '13 at 13:27

score 30 · Answer 1 · answered Oct 09 '13 at 13:35

30

Just do it like that:

[self.collectionView performBatchUpdates:^{
    [self.collectionView reloadSections:[NSIndexSet indexSetWithIndex:0]];
} completion:nil];

answered Oct 09 '13 at 13:35

Fab1n

1,665
14
28

Then you have to dive deeper and write your own ```UICollectionViewLayout```. You cannot compare it with UITableView, because UICollectionView is not only ment to display data in 1D (like UITableView) or 2D (like with UICollectionViewFlowLayout). You are not limited to anything and so there are no trivial animations other than fading built in. It is not possible for custom layouts to use different slide-from-top/bottom/middle animations, because the animations cannot be defined globally!!! – Fab1n Oct 11 '13 at 07:57

score 26 · Answer 2 · answered Oct 27 '16 at 16:58

26

Swift 3 version:

collectionView.performBatchUpdates({
    let indexSet = IndexSet(integer: 0)
    self.collectionView.reloadSections(indexSet)
}, completion: nil)

answered Oct 27 '16 at 16:58

Mark Bridges

7,606
4
43
59

You got leak here. Use `[weak self]` – Szu Sep 20 '18 at 07:55
11

No leak and no need for [weak self]. [weak self] is only needed for long-lived closures that create circular dependencies. This closure does not even escape. – Dag Ågren Oct 13 '18 at 21:02
2

exactly, its non-escaping closure so no need for weak self – Muhammad Waqas Jul 07 '20 at 02:53

score 2 · Answer 3 · answered Aug 18 '16 at 13:29

This article here is worth a read: http://victorlin.me/posts/2016/04/29/uicollectionview-invalid-number-of-items-crash-issue

TLDR:

So it turned out performBatchUpdates calls collectionView(:numberOfItemsInSection:) first before call the given closure to know the item numbers. Next, it calls the closure, and eventually, it calls collectionView(:numberOfItemsInSection:) again to check the number. And here is where the assertion exception thrown.

UICollectionView reloadSections with animation

3 Answers3