Question

我有一个UICollectionView，可以在tvOS下垂直和水平滚动。我想控制每个部分的位置，因此我正在使用setContentOffset属性进行对齐。这很好用，但是，当水平滚动时，单元格返回到我更新contentOffset之前的垂直位置。

UICollectionView的设置：

lazy var singleCollectionView: UICollectionView = {
    let cv = UICollectionView(frame: self.view.bounds, collectionViewLayout: self.generateLayout())
    cv.delegate = self.singleDelegate
    cv.dataSource = self.singleDatasource
    cv.remembersLastFocusedIndexPath = true
    cv.register(DemandCVCell.self, forCellWithReuseIdentifier: "cvCell")
    cv.register(UICollectionReusableView.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: "header")
    cv.register(UICollectionReusableView.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionFooter, withReuseIdentifier: "footer")
    cv.translatesAutoresizingMaskIntoConstraints = false
    return cv
}()

private func generateLayout() -> UICollectionViewLayout {
    let itemSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(0.20), heightDimension: .absolute(200))
    let tileItem = NSCollectionLayoutItem(layoutSize: itemSize)
    tileItem.contentInsets = NSDirectionalEdgeInsets(top: 0, leading: -32, bottom: 0, trailing: 0)

    var tileGroup:NSCollectionLayoutGroup!
    if showType == .bucket {
        let groupSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1.03), heightDimension: .absolute(H_THUMB_SIZE.height))
        tileGroup = NSCollectionLayoutGroup.horizontal(layoutSize: groupSize, subitem: tileItem, count: 3)
    } else {
        let groupSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1.03), heightDimension: .absolute(H_THUMB_SIZE.height))
        tileGroup = NSCollectionLayoutGroup.horizontal(layoutSize: groupSize, subitems: [tileItem])
    }

    let section = NSCollectionLayoutSection(group: tileGroup)
    if showType == .bucket {
        section.orthogonalScrollingBehavior = .none
    } else {
        section.orthogonalScrollingBehavior = .continuous
    }

    let headerSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1.0), heightDimension: .absolute(50.0))
    let header = NSCollectionLayoutBoundarySupplementaryItem(layoutSize: headerSize, elementKind: "header", alignment: .topLeading)
    let footerSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1.0), heightDimension: .absolute(40.0))
    let footer = NSCollectionLayoutBoundarySupplementaryItem(layoutSize: footerSize, elementKind: "footer", alignment: .bottomLeading)
    footer.contentInsets = NSDirectionalEdgeInsets(top: 10, leading: 0, bottom: 0, trailing: 0)
    section.boundarySupplementaryItems = [header,footer]
    let layout = UICollectionViewCompositionalLayout(section: section)

    return layout
}

在代表中，我正在使用以下函数来告知标准Apple滚动何时完成以及将更改动画化为新位置后的情况：

func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
    let visibleSection = collectionView.indexPathsForVisibleItems.first!.section
    guard visibleSection > 0 else {return}
    guard visibleSection < parentVC.topicsArray.count - 1 else {
        scrollView.setContentOffset(CGPoint(x: scrollView.contentOffset.x, y: scrollView.contentOffset.y - 85), animated: true)
        return
    }
    scrollView.setContentOffset(CGPoint(x: scrollView.contentOffset.x, y: scrollView.contentOffset.y + 75), animated: true)
}

一切正常，直到我水平滚动。正如我想要的那样，水平滚动条上没有调用scrollViewDidEndDecelarating。但是，在水平滚动垂直移动collectionview之后，确实会再次调用它。这里的最大问题是，为什么水平滚动行为还会将collectionview垂直移回其原始对齐方式？

UICollectionView垂直ContentOffset与水平滚动问题

0 个答案: