This is a simple collection view with compositional layout and diffable data source.
It displays one cell, of type UICollectionViewListCell
, whose contentView
has a text view as a subview.
import UIKit
class ViewController: UIViewController {
var collectionView: UICollectionView!
let textView = UITextView()
var dataSource: UICollectionViewDiffableDataSource<Section, Int>!
enum Section: CaseIterable {
case first
}
override func viewDidLoad() {
super.viewDidLoad()
configureHierarchy()
configureDataSource()
}
private func configureHierarchy() {
collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: createLayout())
view.addSubview(collectionView)
collectionView.autoresizingMask = [.flexibleHeight, .flexibleWidth]
textView.delegate = self
}
func configureDataSource() {
let cellRegistration = UICollectionView.CellRegistration<UICollectionViewListCell, Int> { [weak self] cell, indexPath, itemIdentifier in
guard let self else { return }
cell.contentView.addSubview(textView)
textView.pinToSuperviewMargins()
}
dataSource = .init(collectionView: collectionView) { collectionView, indexPath, itemIdentifier in
collectionView.dequeueConfiguredReusableCell(using: cellRegistration, for: indexPath, item: itemIdentifier)
}
var snapshot = NSDiffableDataSourceSnapshot<Section, Int>()
snapshot.appendSections(Section.allCases)
snapshot.appendItems([1], toSection: .first)
dataSource.apply(snapshot)
}
func createLayout() -> UICollectionViewLayout {
UICollectionViewCompositionalLayout { section, layoutEnvironment in
var config = UICollectionLayoutListConfiguration(appearance: .insetGrouped)
return NSCollectionLayoutSection.list(using: config, layoutEnvironment: layoutEnvironment)
}
}
}
extension ViewController: UITextViewDelegate {
func textViewDidChange(_ textView: UITextView) {
// Do something here?
}
}
The pinToSuperviewMargins method sets the top, bottom, leading and trailing constraints of the view on which it's called to its superview's and its translatesAutoResizingMaskIntoConstraints property to false:
extension UIView {
func pinToSuperviewMargins(
top: CGFloat = 0,
bottom: CGFloat = 0,
leading: CGFloat = 0,
trailing: CGFloat = 0,
file: StaticString = #file,
line: UInt = #line
) {
guard let superview = self.superview else {
let localFilePath = URL(fileURLWithPath: "\(file)").lastPathComponent
print(">> \(#function) failed in file: \(localFilePath), at line: \(line): could not find \(Self.self).superView.")
return
}
self.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
self.topAnchor.constraint(equalTo: superview.topAnchor, constant: top),
self.bottomAnchor.constraint(equalTo: superview.bottomAnchor, constant: bottom),
self.leadingAnchor.constraint(equalTo: superview.leadingAnchor, constant: leading),
self.trailingAnchor.constraint(equalTo: superview.trailingAnchor, constant: trailing),
])
}
func pinToSuperviewMargins(constant c: CGFloat = 0, file: StaticString = #file, line: UInt = #line) {
self.pinToSuperviewMargins(top: c, bottom: c, leading: c, trailing: c, file: file, line: line)
}
}
I tried calling collectionView.setNeedsLayout()
in textViewDidChange(_:)
but it doesn't work.
I used to accomplish cell resizing with tableView.beginUpdates(); tableView.endUpdates()
when dealing with table views.
Set the selfSizingInvalidation
property on the UICollectionView to .enabledIncludingConstraints
. This will cause the collection view to automatically detect Auto Layout and intrinsic content size changes within the cell, and resize the cell when necessary.
Links to the relevant documentation pages:
https://developer.apple.com/documentation/uikit/uicollectionview/4001100-selfsizinginvalidation