使用组合布局时，我们如何知道cellForRow方法中的具体项

Question

我创建了一个具有组合布局的集合视图，下面是我用于创建布局的代码。

    func getCompositionalLayout() -> UICollectionViewCompositionalLayout {
        
        let item = NSCollectionLayoutItem(layoutSize: NSCollectionLayoutSize(widthDimension: .fractionalWidth(1), heightDimension: .fractionalHeight(1/3)))
        item.contentInsets = NSDirectionalEdgeInsets(top: 1, leading: 1, bottom: 1, trailing: 1)


        //--------- Group 1 ---------//
        let group1Item1 = NSCollectionLayoutItem(layoutSize: NSCollectionLayoutSize(widthDimension: .fractionalWidth(1/2), heightDimension: .fractionalHeight(1)))
        group1Item1.contentInsets = NSDirectionalEdgeInsets(top: 1, leading: 1, bottom: 1, trailing: 1)
        


        let nestedGroup1Item1 = NSCollectionLayoutItem(layoutSize: NSCollectionLayoutSize(widthDimension: .fractionalWidth(1), heightDimension: .fractionalHeight(1/2)))
        nestedGroup1Item1.contentInsets = NSDirectionalEdgeInsets(top: 1, leading: 1, bottom: 1, trailing: 1)

         let nestedGroup2Item1 = NSCollectionLayoutItem(layoutSize: NSCollectionLayoutSize(widthDimension: .fractionalWidth(1/2), heightDimension: .fractionalHeight(1)))
        nestedGroup2Item1.contentInsets = NSDirectionalEdgeInsets(top: 1, leading: 1, bottom: 1, trailing: 1)
        
        let nestedGroup2 = NSCollectionLayoutGroup.horizontal(layoutSize: NSCollectionLayoutSize(widthDimension: .fractionalWidth(1), heightDimension: .fractionalHeight(1/2)), subitems: [nestedGroup2Item1])
        
        let nestedGroup1 = NSCollectionLayoutGroup.vertical(layoutSize: NSCollectionLayoutSize(widthDimension: .fractionalWidth(1/2), heightDimension: .fractionalHeight(1)), subitems: [nestedGroup1Item1, nestedGroup2])

        let group1 = NSCollectionLayoutGroup.horizontal(layoutSize: NSCollectionLayoutSize(widthDimension: .fractionalWidth(1), heightDimension: .fractionalHeight(1/3)), subitems: [group1Item1, nestedGroup1])


        //--------- Group 2 ---------//
        let group2Item1 = NSCollectionLayoutItem(layoutSize: NSCollectionLayoutSize(widthDimension: .fractionalWidth(1/3), heightDimension: .fractionalHeight(1)))
        group2Item1.contentInsets = NSDirectionalEdgeInsets(top: 1, leading: 1, bottom: 1, trailing: 1)

        let group2 = NSCollectionLayoutGroup.horizontal(layoutSize: NSCollectionLayoutSize(widthDimension: .fractionalWidth(1), heightDimension: .fractionalHeight(1/3)), subitems: [group2Item1])


        //--------- Container Group ---------//
        let containerGroup = NSCollectionLayoutGroup.vertical(layoutSize: NSCollectionLayoutSize(widthDimension: .fractionalWidth(1), heightDimension: .absolute(600)), subitems: [item, group1, group2])

        let section = NSCollectionLayoutSection(group: containerGroup)
        let layout = UICollectionViewCompositionalLayout(section: section)
        return layout

}

使用这段代码，我的集合视图看起来像这样

现在我的问题是如何知道每次在 cellForItem 方法中出现的红细胞，以便我可以显示其中的不同内容。 （就像 Instagram 在其搜索页面上以更大的单元格显示视频一样）。

无法识别红细胞（位于第 1 组，名称为 group1Item1）

Answer 1

观察您的布局每 8 个单元格“重复”一次。即它的周期为 8。这 8 个单元格总是自我重复：

我们可以看到，您要识别的红细胞是这 8 个细胞序列中的第二个。红细胞的索引为 1、9、17、25 等。因此，我们可以简单地检查除以 8 的余数：

if indexPath.row % 8 == 1 {
    // this is the red cell
} else {
    // something else
}