I have two UICollectionViews, UICV1 which has UICV2 nested within one of its cells. What I want is that UICV2 self-sizes according to its content, but both the contentSize and collectionViewLayout.collectionViewContentSize is zero.
This exact same setup worked before, the only difference is that UICV2 was a UITableView. Due to code refactoring and reuse, I switched to using UICollectionView. The new view hierarchy looks something like that:
+--------------------+
| UICV1 |
| +----------------+ |
| | Cell | |
| | +------------+ | |
| | | Stack View | | |
| | | +--------+ | | |
| | | | UICV2 | | | |
| | | +--------+ | | |
| | +------------+ | |
| +----------------+ |
| ... |
+--------------------+
Both collection views are configured with a UICollectionViewCompositionalLayout:
// UICV1
let layout1 = UICollectionViewCompositionalLayout { sectionIndex, layoutEnvironment in
let itemSize = NSCollectionLayoutSize(
widthDimension: .fractionalWidth(1.0),
heightDimension: .estimated(100)
)
let item = NSCollectionLayoutItem(layoutSize: itemSize)
let group = NSCollectionLayoutGroup.horizontal(
layoutSize: itemSize,
subitem: item,
count: 1
)
return NSCollectionLayoutSection(group: group)
}
// UICV2
let layout2 = UICollectionViewCompositionalLayout.list(using: {
var configuration = UICollectionLayoutListConfiguration(appearance: .insetGrouped)
configuration.headerMode = .none
configuration.headerTopPadding = 0
return configuration
}())
let collectionView = SelfSizingCollectionView(
frame: .zero,
collectionViewLayout: layout2
)
This is the code for the self sizing collection view:
class SelfSizingCollectionView: UICollectionView {
override init(frame: CGRect, collectionViewLayout layout: UICollectionViewLayout) {
super.init(frame: frame, collectionViewLayout: layout)
isScrollEnabled = false
contentInsetAdjustmentBehavior = .never
}
override var contentSize: CGSize {
didSet {
invalidateIntrinsicContentSize()
}
}
override func layoutSubviews() {
super.layoutSubviews()
invalidateIntrinsicContentSize()
}
override var intrinsicContentSize: CGSize {
layoutIfNeeded()
// This is always (0.0, 0.0)
return CGSize(
width: UIView.noIntrinsicMetric,
height: collectionViewLayout.collectionViewContentSize.height
)
}
}
I am using a NSDiffableDataSourceSnapshot for providing data to both collection views, if this makes any difference.
I hope someone could help me here, I'm totally lost after playing with combinations of invalidateLayout(), setNeedsLayout() and layoutIfNeeded() at various points within SelfSizingCollectionView.
I found a ton of answers regarding self-sizing collection views, which I incorporated into my code, but they don't seem to work for the quite new UICollectionViewCompositionalLayout.
