问题描述
是的,我已经检查了有关此主题的其他问题。由于某种原因,该功能
override func scrollViewDidScroll(_ scrollView: UIScrollView) {
print(scrollView.contentOffset)
}
未在我的UICollectionView类中调用。
这是全班。当用户在每个单元格上滑动时,我基本上想更新pageControl。
我尝试了collectionView:willDisplayCell:forItemAtIndexPath:
方法,但发现有时当我滚动并在单元格中途停止并返回时,它并没有更新为先前的值。因此,为什么我求助于scrollview委托。
class FilterInfoImagesCollectionViewController: UICollectionViewController {
var selectedFilterCollection: FilterCollection!
private let pageControl: UIPageControl = {
let pageControl = UIPageControl()
pageControl.currentPage = 0
pageControl.numberOfPages = 5 // Hardcoded since we know there will only be 5 example images
pageControl.translatesAutoresizingMaskIntoConstraints = false
return pageControl
}()
private var datasource: DataSource!
private var datas = [FilterInfo]()
override func viewDidLoad() {
super.viewDidLoad()
collectionView.alwaysBounceVertical = false
collectionView.isPagingEnabled = true
collectionView.register(FilterInfoCollectionViewCell.self,forCellWithReuseIdentifier: FilterInfoCollectionViewCell.ReuseIdentifier)
collectionView.collectionViewLayout = createLayout()
collectionView.backgroundColor = .clear
collectionView.delegate = self
collectionView.dataSource = self
configureDatasource()
setupDatas()
setupView()
setupConstraint()
}
private func setupDatas() {
let filterName = selectedFilterCollection.name.components(separatedBy: " ").first!
for n in 1 ... 5 {
let image = UIImage(named: "\(filterName).ex\(n)")
let filterInfo = FilterInfo(image: image,filterName: "\(filterName)\(n)")
datas.append(filterInfo)
}
self.createSnapshot(from: datas)
}
private func setupView() {
self.view.addSubview(pageControl)
}
private func setupConstraint() {
pageControl.snp.makeConstraints { (make) in
make.centerX.equalToSuperview()
make.bottom.equalToSuperview()
}
}
}
extension FilterInfoImagesCollectionViewController {
fileprivate enum Section { case main }
fileprivate typealias DataSource = UICollectionViewDiffableDataSource<Section,FilterInfo>
fileprivate typealias Snapshot = NSDiffableDataSourceSnapshot<Section,FilterInfo>
fileprivate func configureDatasource() {
datasource = DataSource(collectionView: collectionView!,cellProvider: { (collectionView,indexPath,filterInfo) -> UICollectionViewCell? in
guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: FilterInfoCollectionViewCell.ReuseIdentifier,for: indexPath) as? FilterInfoCollectionViewCell else { return nil }
cell.filterInfo = filterInfo
return cell
})
}
fileprivate func createSnapshot(from datas: [FilterInfo]) {
var snapshot = Snapshot()
snapshot.appendSections([.main])
snapshot.appendItems(datas)
datasource.apply(snapshot,animatingDifferences: true)
}
private func createLayout() -> UICollectionViewLayout {
let itemSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1),heightDimension: .fractionalHeight(1))
let item = NSCollectionLayoutItem(layoutSize: itemSize)
let groupSize = NSCollectionLayoutSize(
widthDimension: .fractionalWidth(1),heightDimension: .fractionalHeight(1))
let group = NSCollectionLayoutGroup.horizontal(layoutSize: groupSize,subitem: item,count: 1)
let section = NSCollectionLayoutSection(group: group)
section.orthogonalScrollingBehavior = .groupPaging
let layout = UICollectionViewCompositionalLayout(section: section)
return layout
}
}
extension FilterInfoImagesCollectionViewController {
override func scrollViewDidScroll(_ scrollView: UIScrollView) {
print(scrollView.contentOffset)
}
}
为什么不叫它?我尝试与其他scrollview委托方法进行检查,并且发生相同的事情-未调用。
更新:根据请求将委托和数据源添加到自身
解决方法
添加viewDidLoad。与UICollectionViewDelegate相关的滚动功能,您需要设置代理以使用覆盖功能
section.visibleItemsInvalidationHandler = { [weak self] visibleItems,point,environment in
self?.pager.currentPage = visibleItems.last!.indexPath.row
}