collectionView(_:willDisplaySupplementaryView:forElementKind:at:)
Tells the delegate that the specified supplementary view is about to be displayed in the collection view.
Declaration
optional func collectionView(_ collectionView: UICollectionView, willDisplaySupplementaryView view: UICollectionReusableView, forElementKind elementKind: String, at indexPath: IndexPath)Parameters
- collectionView:
The collection view object that is adding the supplementary view.
- view:
The view being added.
- elementKind:
The type of the supplementary view. This string is defined by the layout that presents the view.
- indexPath:
The index path of the data item that the supplementary view represents.
Discussion
The collection view calls this method before adding a supplementary view to its content. Use this method to detect view additions, as opposed to monitoring the view itself to see when it appears.