UICollectionView sectionInsets not respected when using Header Cells - ios

Question

I am trying to create a collection view that has a header cell (dynamically sized) and some "normal" content cells (also dynamically sized). Therefore, the collection view is initialized as follows:
private lazy var timelineCollectionView: UICollectionView = {
let flowLayout = UICollectionViewFlowLayout()
flowLayout.scrollDirection = .vertical
flowLayout.sectionInset = UIEdgeInsets(top: self.coloredTitleBarHeight, left: 0, bottom: 0, right: 0) // assume that coloredTitlebarHeight is a constant of 120
flowLayout.estimatedItemSize = CGSize(width: self.view.frame.width, height: 10)
flowLayout.minimumInteritemSpacing = 0
flowLayout.minimumLineSpacing = 0
let cv = UICollectionView(frame: .zero, collectionViewLayout: flowLayout)
cv.alwaysBounceVertical = true
cv.contentInsetAdjustmentBehavior = .never
cv.backgroundColor = .clear
cv.scrollIndicatorInsets = UIEdgeInsets(top: self.coloredTitleBarHeight - self.getStatusBarHeight(), left: 0, bottom: 0, right: 0)
cv.delegate = self
cv.dataSource = self
cv.register(TLContentCell.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: "content-header-cell")
cv.register(TLContentCell.self, forCellWithReuseIdentifier: "comment-cell")
return cv
}()
The collectionView is part of a ViewController that conforms to the following protocols: UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout
Then, I use the following code to create a header cell:
func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
let cell = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: "content-header-cell", for: indexPath) as! TLContentCell
cell.timelineContent = tlContentItem
cell.delegate = self
return cell
}
Last but not least, the dequeuing of the regular cells:
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 1
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "comment-cell", for: indexPath)
return cell
}
Output:
The collectionView displays the header cell as well as the item cells, however, the section Insets are not applied.
I would be very happy if you could provide me with any suggestion regarding this strange behavior.

Answer 1

Section insets are applied to contents only in UICollectionViewFlowLayout.
Using Section Insets to Tweak the Margins of Your Content
Section insets are a way to adjust the space available for laying out cells.
You can use insets to insert space after a section’s header view and
before its footer view. You can also use insets to insert space around
the sides of the content. Figure 3-5 demonstrates how insets affect
some content in a vertically scrolling flow layout. source