UICollectionView custom layout. Supplementary views are not shown or queried

Question

I am trying to create a simple custom layout for UICollectionView to use programmatically (i.e. without Interface Builder).

I do everything according to the docs:

1. Subclass UICollectionViewLayout and prepare my layout
2. override layoutAttributesForSupplementaryView(ofKind elementKind: String, at indexPath: IndexPath) and return corresponding layout attributes
3. add collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) implementation where I return my supplementary view

My problem is that neither

collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath)

nor

layoutAttributesForSupplementaryView(ofKind elementKind: String, at indexPath: IndexPath)

is getting called, so I can't see my supplementary views.

I have double-checked my implementations both for layout and for supplementary views creation but I still can't get it to work.

Answer 1

Apparently it is not enough to have

layoutAttributesForSupplementaryView(ofKind elementKind: String, at indexPath: IndexPath) -> UICollectionViewLayoutAttributes?

which return attributes for supplementary views. One also needs to return attributes for supplementary views in

layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes?

My mistake was that I was only returning layout attributes for cells in

layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes?

Once I added layout attributes for supplementary views into values returned by

layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes?

I got my datasource methods called and supplementary views returned.

EDIT: This answer covers iOS10 SDK. I haven't tried on earlier versions