Question

我正在实现UICollectionViewCompositionalLayout并使用

section.orthogonalScrollingBehavior = .groupPagingCentered

水平滚动部分。

这使用户可以在一个部分中水平滚动页面。

我使用

section.visibleItemsInvalidationHandler = {...}

获取用户滚动到的页面。

如何以编程方式滚动到此部分中的页面？

Answer 1

我实际上使它正常工作。该代码适用于XCode 12 Beta 2 /目标iOS14 / Swift 5.1。

在这段代码中，请特别注意间距，插图和正交滚动行为！！！

fileprivate func configureCollectionViewLayout() {
    func createLayout() -> UICollectionViewLayout {
        self.collectionView.canCancelContentTouches = false
        let layout = UICollectionViewCompositionalLayout {
            (sectionIndex: Int, layoutEnvironment: NSCollectionLayoutEnvironment) -> NSCollectionLayoutSection? in
            
            guard let sectionKind = Section(rawValue: sectionIndex) else { return nil }
            let spacing = CGFloat(10)

            switch sectionKind {
            case .someOtherSection:
                // configure the layout for this section
            case .yetAnotherSection:
                // configure the layout for this section
            case .sectionWithOrthogonalScrollingBehaviour:
                let itemSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1.0), heightDimension: .fractionalHeight(1.0))
                let item = NSCollectionLayoutItem(layoutSize: itemSize)
                let groupSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1.0), heightDimension: .fractionalWidth(1.0*9.0/16.0))
                let group = NSCollectionLayoutGroup.horizontal(layoutSize: groupSize, subitems: [item])
                let section = NSCollectionLayoutSection(group: group)
                group.interItemSpacing = .fixed(0) // should (probably) be 0 otherwise there is an offset when scrollingToIndex
                section.interGroupSpacing = 0 // should (probably) be 0 otherwise there is an offset when scrollingToIndex
                section.contentInsets = NSDirectionalEdgeInsets(top: 10, leading: 0, bottom: 0, trailing: 0) // leading and trailing should (certainly) be 0 otherwise the pages are offsetted in relation to the view
                section.orthogonalScrollingBehavior = .continuous // should be continous, otherwise it won't work
                return section
            }
        }
        return layout
    }
    collectionView.collectionViewLayout = createLayout()
}

为了以编程方式滚动，我实现了分段控件。当用户点击一个片段时，正交滚动部分会自动滚动到与所选片段相对应的单元格。

@IBAction func segmentedControlValueChanged(_ sender: UISegmentedControl) {
    
    // determine which Item belongs to the selected segment. In my case Items in a Section are represented by an enum called 'Item'

    let dataSourceIndexPath = self.dataSource.indexPath(for: .itemCase)
    let pressentationIndexPath = self.collectionView.presentationIndexPath(forDataSourceIndexPath: dataSourceIndexPath)! // This step is necessary, otherwise the next line does not have have wanted behaviour (I'm force unwrapping here to simplify. Don't do that in your final code)
    self.collectionView.scrollToItem(at: pressentationIndexPath, at: .centeredHorizontally, animated: true) // make sure you use .centeredHorizontally
}

我不确定这是Apple打算如何使用它。在下一个Xcode beta版本中，它可能会再次制动。

旁注：如果您想知道为什么我需要/想要细分滚动收藏视图的控件：这是因为正交滚动部分中的单元需要消耗水平平移手势（所有单元格都是您可以移动手指的图表然后在触摸的位置显示图表值）。是的...我知道这也可以通过其他方式完成，但是我想使用合成布局，因为它与其他部分，我想保持这种甜美的内置动画正交滚动行为（即使现在已经部分丢失，因为正交滚动行为需要保持.Continues才能正常工作），我只是想看看它是否可以完成：）

UICollectionViewCompositionalLayout设置section.orthogonalScrollingBehavior页面以编程方式进行？

1 个答案: