UICollectionView header not showing

Question

I'm working on a project that uses an UICollectionView to show several albums. The items show fine, but now I want to show an header above the first section.

To do this, I added the registerNib:forSupplementaryViewOfKind:withReuseIdentifier: to my init method. Like this:

[self.collectionView registerNib:[UINib nibWithNibName:@"AlbumHeader" bundle:nil] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:kAlbumHeaderIdentifier];

(The AlbumHeader Nib contains a view of the class AlbumHeader, which is a subclass of UICollectionView.)

After that, I implemented collectionView:viewForSupplementaryElementOfKind:atIndexPath method:

- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {
    return [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:kAlbumHeaderIdentifier forIndexPath:indexPath];
}

Now it should try to load the header view, I suppose. But it doesn't, the method for the supplementary view doesn't get called.

What am I missing? Stuck for hours, have read the documentation on UICollectionViews many times, but nothing seems to help. Any thoughts?

Answer 1

After looking for the method yuf asked about, I read that by default the size of headers/footers are 0,0. If the size is 0, the header/footer won't display.

You can set the size with a property:

flowLayout.headerReferenceSize = CGSizeMake(0, 100);

Then all the headers will have the same size. If it has to be different for each section, you can implement the following method, which is part of the UICollectionViewDelegateFlowLayout protocol.

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section {
    if (section == albumSection) {
        return CGSizeMake(0, 100);
    }

    return CGSizeZero;
}

Note that in vertical scrolling it uses the returned height and the full width of the collection view, in horizontal scrolling it uses the return width and the full height of the collection view.