Question
How to use didSelectItemAt method with using UICollectionView?
I have a UICollectionViewCompositionalLayout
. And I want to change label on cell click.
I use this code to do it:
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: MediumTableCell.reuseIdentifier, for: indexPath) as! MediumTableCell
cell.title.text = "true"
}
But it is doesn't work. How to fix it?
Full code:
Cell code:
import UIKit
class MediumTableCell: UICollectionViewCell, SelfConfiguringCell {
static let reuseIdentifier: String = "MediumTableCell"
let title = UILabel()
override init(frame: CGRect) {
super.init(frame: frame)
title.font = UIFont.preferredFont(forTextStyle: .headline)
title.textColor = .label
contentView.addSubview(title)
NSLayoutConstraint.activate([
title.leadingAnchor.constraint(equalTo: contentView.leadingAnchor),
title.trailingAnchor.constraint(equalTo: contentView.trailingAnchor),
title.topAnchor.constraint(equalTo: contentView.topAnchor)
])
}
func configure(with app: App) {
title.text = app.name
}
required init?(coder: NSCoder) {
fatalError("Just… no")
}
}
Controller code:
class AppsViewController: UIViewController, UICollectionViewDelegate {
let sections = Bundle.main.decode([Section].self, from: "appstore.json")
var collectionView: UICollectionView!
var dataSource: UICollectionViewDiffableDataSource<Section, App>?
override func viewDidLoad() {
super.viewDidLoad()
collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: createCompositionalLayout())
collectionView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
collectionView.backgroundColor = .systemBackground
collectionView.delegate = self
view.addSubview(collectionView)
collectionView.register(SectionHeader.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: SectionHeader.reuseIdentifier)
collectionView.register(FeaturedCell.self, forCellWithReuseIdentifier: FeaturedCell.reuseIdentifier)
collectionView.register(MediumTableCell.self, forCellWithReuseIdentifier: MediumTableCell.reuseIdentifier)
collectionView.register(SmallTableCell.self, forCellWithReuseIdentifier: SmallTableCell.reuseIdentifier)
createDataSource()
reloadData()
}
func configure<T: SelfConfiguringCell>(_ cellType: T.Type, with app: App, for indexPath: IndexPath) -> T {
guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellType.reuseIdentifier, for: indexPath) as? T else {
fatalError("Unable to dequeue \(cellType)")
}
cell.configure(with: app)
return cell
}
func createDataSource() {
dataSource = UICollectionViewDiffableDataSource<Section, App>(collectionView: collectionView) { collectionView, indexPath, app in
switch self.sections[indexPath.section].type {
case "mediumTable":
return self.configure(MediumTableCell.self, with: app, for: indexPath)
case "smallTable":
return self.configure(SmallTableCell.self, with: app, for: indexPath)
default:
return self.configure(FeaturedCell.self, with: app, for: indexPath)
}
}
dataSource?.supplementaryViewProvider = { [weak self] collectionView, kind, indexPath in
guard let sectionHeader = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: SectionHeader.reuseIdentifier, for: indexPath) as? SectionHeader else {
return nil
}
guard let firstApp = self?.dataSource?.itemIdentifier(for: indexPath) else { return nil }
guard let section = self?.dataSource?.snapshot().sectionIdentifier(containingItem: firstApp) else { return nil }
if section.title.isEmpty { return nil }
sectionHeader.title.text = section.title
sectionHeader.subtitle.text = section.subtitle
return sectionHeader
}
}
func reloadData() {
var snapshot = NSDiffableDataSourceSnapshot<Section, App>()
snapshot.appendSections(sections)
for section in sections {
snapshot.appendItems(section.items, toSection: section)
}
dataSource?.apply(snapshot)
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: MediumTableCell.reuseIdentifier, for: indexPath) as! MediumTableCell
cell.title.text = "true"
}
func createCompositionalLayout() -> UICollectionViewLayout {
let layout = UICollectionViewCompositionalLayout { sectionIndex, layoutEnvironment in
let section = self.sections[sectionIndex]
switch section.type {
case "mediumTable":
return self.createMediumTableSection(using: section)
case "smallTable":
return self.createSmallTableSection(using: section)
default:
return self.createFeaturedSection(using: section)
}
}
let config = UICollectionViewCompositionalLayoutConfiguration()
config.interSectionSpacing = 20
layout.configuration = config
return layout
}
func createFeaturedSection(using section: Section) -> NSCollectionLayoutSection {
let itemSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1), heightDimension: .fractionalHeight(1))
let layoutItem = NSCollectionLayoutItem(layoutSize: itemSize)
layoutItem.contentInsets = NSDirectionalEdgeInsets(top: 0, leading: 5, bottom: 0, trailing: 5)
let layoutGroupSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(0.93), heightDimension: .estimated(350))
let layoutGroup = NSCollectionLayoutGroup.horizontal(layoutSize: layoutGroupSize, subitems: [layoutItem])
let layoutSection = NSCollectionLayoutSection(group: layoutGroup)
layoutSection.orthogonalScrollingBehavior = .groupPagingCentered
return layoutSection
}
func createMediumTableSection(using section: Section) -> NSCollectionLayoutSection {
let itemSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1), heightDimension: .fractionalHeight(0.33))
let layoutItem = NSCollectionLayoutItem(layoutSize: itemSize)
layoutItem.contentInsets = NSDirectionalEdgeInsets(top: 0, leading: 5, bottom: 0, trailing: 5)
let layoutGroupSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(0.93), heightDimension: .fractionalWidth(0.55))
let layoutGroup = NSCollectionLayoutGroup.vertical(layoutSize: layoutGroupSize, subitems: [layoutItem])
let layoutSection = NSCollectionLayoutSection(group: layoutGroup)
layoutSection.orthogonalScrollingBehavior = .groupPagingCentered
let layoutSectionHeader = createSectionHeader()
layoutSection.boundarySupplementaryItems = [layoutSectionHeader]
return layoutSection
}
func createSmallTableSection(using section: Section) -> NSCollectionLayoutSection {
let itemSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1), heightDimension: .fractionalHeight(0.2))
let layoutItem = NSCollectionLayoutItem(layoutSize: itemSize)
layoutItem.contentInsets = NSDirectionalEdgeInsets(top: 0, leading: 20, bottom: 0, trailing: 0)
let layoutGroupSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(0.93), heightDimension: .estimated(200))
let layoutGroup = NSCollectionLayoutGroup.vertical(layoutSize: layoutGroupSize, subitems: [layoutItem])
let layoutSection = NSCollectionLayoutSection(group: layoutGroup)
let layoutSectionHeader = createSectionHeader()
layoutSection.boundarySupplementaryItems = [layoutSectionHeader]
return layoutSection
}
func createSectionHeader() -> NSCollectionLayoutBoundarySupplementaryItem {
let layoutSectionHeaderSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(0.93), heightDimension: .estimated(80))
let layoutSectionHeader = NSCollectionLayoutBoundarySupplementaryItem(layoutSize: layoutSectionHeaderSize, elementKind: UICollectionView.elementKindSectionHeader, alignment: .top)
return layoutSectionHeader
}
}
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