UICollectionViewCompositionalLayout 水平，使用估计和不水平拥抱时不计算内容的宽度

Question

I want the cell to horizontaly Hug its content

我在水平模式下使用 UICollectionViewCompositionalLayout 并且 widthDimension: .estimated(100) 应该计算内容大小

但单元格/组的宽度根本不是根据内容大小计算的 并设置为估计值，因为它是绝对值

即使向标签添加宽度限制也不会影响单元格大小

这是预期的行为吗？如果是，那为什么？以及如何得到想要的结果？

class LabelCell: UICollectionViewCell {
    @IBOutlet weak var label: UILabel!
}

class ViewController: UIViewController, UICollectionViewDataSource {

    func buildLayout() -> UICollectionViewCompositionalLayout {

        let itemSize = NSCollectionLayoutSize(widthDimension: .estimated(100), heightDimension: .absolute(32))
        let item = NSCollectionLayoutItem(layoutSize: itemSize)

        let groupSize = NSCollectionLayoutSize(widthDimension: .estimated(100), heightDimension: .absolute(32))
        let group = NSCollectionLayoutGroup.horizontal(layoutSize: groupSize, subitem: item, count: 1)

        let section = NSCollectionLayoutSection(group: group)
        section.interGroupSpacing = 10

        let configuration = UICollectionViewCompositionalLayoutConfiguration()
        configuration.scrollDirection = .horizontal
        return UICollectionViewCompositionalLayout(section: section, configuration: configuration)

    }

    @IBOutlet weak var collectionView: UICollectionView!

    let items = ["1", "12", "12345", "123456789"]

    override func viewDidLoad() {
        super.viewDidLoad()
        collectionView.collectionViewLayout = buildLayout()
    }

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return items.count
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let c = collectionView.dequeueReusableCell(withReuseIdentifier: "LabelCell", for: indexPath) as! LabelCell
        c.label.text = items[indexPath.row]
        return c
    }
}

Answer 1

要正确调整单元格大小，请更改：

let group = NSCollectionLayoutGroup.horizontal(layoutSize: groupSize, subitem: item, count: 1)

为此：

let group = NSCollectionLayoutGroup.horizontal(layoutSize: groupSize, subitems: [item])

我不确定为什么需要进行此更改，因为这些行似乎在表达相同的意思。也就是说，只要您的集合视图单元格通过覆盖 sizeThatFits(_:)、preferredLayoutAttributesFitting(_:)、使用自动布局等指定实际单元格大小，它就可以工作

关于它的价值，第一个函数签名的文档说：

Specifies a group that will have N items equally sized along the horizontal axis.

第二个函数签名的注释没有对大小相同的项目提出此类声明。它说：

Specifies a group that will repeat items until available horizontal space is exhausted.

UICollectionViewCompositionalLayout 水平，使用估计和不水平拥抱时不计算内容的宽度

UICollectionViewCompositionalLayout horizontal, not calculating width of content when using estimated and not horizontally hugging

cocoa-touch

uicollectionview

uicollectionviewlayout

swift

uicollectionviewcompositionallayout