Question

I have a custom UICollectionViewCell subclass that overwrites initWithFrame: and layoutSubviews to setup its views. However, I’m now trying to do two things which I’m having trouble with.

1) I’m trying to customize the state of the UICollectionViewCell upon selection. For example, I want to change one of the images in an UIImageView in the UICollectionViewCell.

2) I want to animate (light bounce) the UIImage in the UICollectionViewCell.

Can anyone point me in the right direction?

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
    MyCollectionViewCell *cell = (MyCollectionViewCell *)[collectionView cellForItemAtIndexPath:indexPath];
    [cell setSelected:YES];
}

Answer 1

Add a public method performSelectionAnimations to the definition of MyCollectionViewCell that changes the desired UIImageView and performs the desired animation. Then call it from collectionView:didSelectItemAtIndexPath:.

So in MyCollectionViewCell.m:

- (void)performSelectionAnimations {
    // Swap the UIImageView
    ...

    // Light bounce animation
    ...
}

And in your UICollectionViewController:

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
    MyCollectionViewCell *cell = (MyCollectionViewCell *)[collectionView cellForItemAtIndexPath:indexPath];
    [cell performSelectionAnimations];
}

Notice I’ve taken out the call to [cell setSelected:YES], since that should already be taken care of by the UICollectionView. From the documentation:

The preferred way to select the cell and highlight it is to use the selection methods of the collection view object.