I have been stuck on this weird problem for a little while and cannot seem to figure it out.
Setup
- A is a
UICollectionView - Bs are A's
UICollectionViewCells C is a
UICollectionViewadded as a subview of B when the user taps in B+------------------------------+ |A | | | | +----------+ +----------+ | | |B | |B | | | |----------| | | | | | | | | | | |C | | | | | +----------+ +----------+ | +------------------------------+
Issue
When initializing C's UICollectionViewFlowLayout scroll direction property to .horizontal, and scrolling past the second cell, C's cells are vanishing.
As a bonus C itself is vanishing from the UI: the user is again able to tap into the cell, which performs all the actions done on C's usual removal. When tapping again to normally re-show it, actions triggered on C's displaying are fired but C is still visually nowhere to be found.
The issue does not happen when scroll direction is set to .vertical.
Has anyone encountered a similar issue or any clue as to what's going on here?
Thanks in advance.
EDIT Actual implementation
(B)
import UIKit
class CollectionViewCell: UICollectionViewCell {
//...
private let cellId = "cellId"
private lazy var label: UILabel = {
return CollectionViewCell._label()
}()
fileprivate lazy var gallery: UICollectionView = {
return CollectionViewCell._gallery()
}()
//...
override init(frame: CGRect) {
super.init(frame: frame)
isOpaque = true
clipsToBounds = true
layer.borderWidth = 1.5
layer.cornerRadius = 8
// ...
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
private func onSwitchDisplayGallery(_ isDiplaying: Bool) {
switch isDiplaying {
case true:
addSubview(label)
label.topAnchor.constraint(equalTo: topAnchor).isActive = true
label.leftAnchor.constraint(equalTo: leftAnchor).isActive = true
label.widthAnchor.constraint(equalTo: widthAnchor).isActive = true
label.heightAnchor.constraint(equalToConstant: frame.height / 5.25).isActive = true
gallery.register(NestedCollectionViewCell.self, forCellWithReuseIdentifier: cellId)
gallery.delegate = self
addSubview(gallery)
gallery.topAnchor.constraint(equalTo: label.bottomAnchor).isActive = true
gallery.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true
gallery.widthAnchor.constraint(equalTo: widthAnchor).isActive = true
gallery.heightAnchor.constraint(equalTo: heightAnchor, constant: -frame.height / 5.25).isActive = true
case false:
print("removed cv")
// ...
}
}
//...
}
extension CollectionViewCell: UICollectionViewDelegateFlowLayout {
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return gallery.frame.size
}
}
private extension CollectionViewCell {
class func _gallery() -> UICollectionView {
let layout = UICollectionViewFlowLayout()
layout.minimumInteritemSpacing = 0
layout.minimumLineSpacing = 0
layout.scrollDirection = .horizontal
let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
cv.isPagingEnabled = true
cv.showsHorizontalScrollIndicator = false
cv.translatesAutoresizingMaskIntoConstraints = false
return cv
}
class func _label() -> UILabel {
let label = UILabel()
label.font = UIFont(name: "Montserrat-Regular", size: 15)
label.textColor = .white
label.translatesAutoresizingMaskIntoConstraints = false
return label
}
}
(C)
import UIKit
class NestedCollectionViewCell: UICollectionViewCell {
private let containerView = NestedCollectionViewCell._containerView()
override init(frame: CGRect) {
super.init(frame: frame)
isOpaque = true
clipsToBounds = true
backgroundColor = .white
addSubview(containerView)
containerView.centerXAnchor.constraint(equalTo: centerXAnchor).isActive = true
containerView.centerYAnchor.constraint(equalTo: centerYAnchor).isActive = true
containerView.widthAnchor.constraint(equalTo: widthAnchor).isActive = true
containerView.heightAnchor.constraint(equalTo: heightAnchor).isActive = true
//...
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
private extension NestedCollectionViewCell {
class func _containerView() -> UIImageView {
let view = UIImageView()
view.contentMode = .scaleAspectFill
view.translatesAutoresizingMaskIntoConstraints = false
return view
}
}
EDIT 2 I have tried Nick's answer here.
When the scroll direction is set to .vertical, everything is normal.
When it is set to .horizontal C displays no cell...
