Nimrod7 Nimrod7 - 1 year ago 140
iOS Question

UICollectionView animate data change

In my Project I use UICollectionView to display a grid of icons.

The user is able to change the ordering by clicking a segmented control which calling a fetch from core data with different NSSortDescriptor.

The amount of data is always the same, just ending up in different sections / rows:

- (IBAction)sortSegmentedControlChanged:(id)sender {

_fetchedResultsController = nil;
_fetchedResultsController = [self newFetchResultsControllerForSort];

NSError *error;
if (![self.fetchedResultsController performFetch:&error]) {
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);

[self.collectionView reloadData];

The problem is that reloadData doesn't animate the change, UICollectionView just pops with the new data.

Should I keep track in which indexPath a cell was before and after change, and use [self.collectionView moveItemAtIndexPath: toIndexPath:] to perform the animation for the change or there is a better method ?

I didn't get much into subclassing collectionViews so any help will be great...


Answer Source

reloadData doesn't animate, nor does it reliabably do so when put in a UIView animation block. It wants to be in a UICollecitonView performBatchUpdates block, so try something more like:

[self.collectionView performBatchUpdates:^{
    [self.collectionView reloadData];
} completion:^(BOOL finished) {}];
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