swift - 以编程方式限制 UICollectionViewCell 的动态高度？

Question

我从来没有见过比为 Collection View 单元格设置动态高度有如此多不同答案的主题。一些解决方案具有难以想象的代码量，这只会进一步加深人们的共识:UICollectionView 是一个集群，因为这可以通过 UITableView 来实现，而无需执行任何操作，因为动态单元格当约束被正确链接时，高度是内置的。但我想更好地处理 Collection View 。这是一场噩梦。

如何在 Swift 中以编程方式(无 Storyboard)将 Collection View 单元格的高度设置为其内容大小的动态，而无需一百行代码？

您可以将以下内容插入到一个空白项目中，如果您愿意的话，它将运行干净。

CollectionViewFlowLayout:

class CollectionViewFlowLayout: UICollectionViewFlowLayout {

    // inits
    override init() {
        super.init()

        config()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    // config
    func config() {
        scrollDirection = .vertical
        minimumLineSpacing = 0
        minimumInteritemSpacing = 0
    }
}

CollectionViewController

class CollectionViewController: UICollectionViewController, UICollectionViewDelegateFlowLayout {

    // model properties
    let colorArray: [UIColor] = [.red, .green, .blue, .yellow]
    let labelArray: [String] = [
        "sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf",
        "sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf",
        "sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf",
        "sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf sconewolf"
    ]

    // view did load
    override func viewDidLoad() {
        super.viewDidLoad()

        config()
    }

    // config
    func config() {
        collectionView?.dataSource = self
        collectionView?.delegate = self
        collectionView?.backgroundColor = UIColor.gray
        collectionView?.contentInset = UIEdgeInsets(top: -20, left: 0, bottom: 0, right: 0)
        collectionView?.alwaysBounceVertical = true
        collectionView?.alwaysBounceHorizontal = false
        collectionView?.register(CollectionViewCell.self, forCellWithReuseIdentifier: "cell1")
    }

    // data source: number of items in section
    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return colorArray.count
    }

    // data source: cell for item
    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell1", for: indexPath) as! CollectionViewCell
        cell.backgroundColor = colorArray[indexPath.item]
        cell.label.text = labelArray[indexPath.item]
        return cell
    }

    // delegate: size for item
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {

        return CGSize(width: view.frame.width, height: 200)
    }
}

CollectionViewCell

class CollectionViewCell: UICollectionViewCell {

    // view properties
    var label = UILabel()

    // inits
    override init(frame: CGRect) {
        super.init(frame: frame)

        config()
        addLabel()
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    // config
    func config() {
        self.translatesAutoresizingMaskIntoConstraints = false
    }

    // add label
    func addLabel() {
        label.font = UIFont.boldSystemFont(ofSize: 18)
        label.textColor = UIColor.black
        label.numberOfLines = 0
        label.translatesAutoresizingMaskIntoConstraints = false
        addSubview(label)
        label.leadingAnchor.constraint(equalTo: self.leadingAnchor).isActive = true
        label.topAnchor.constraint(equalTo: self.topAnchor).isActive = true
        label.widthAnchor.constraint(equalTo: self.widthAnchor).isActive = true
        label.trailingAnchor.constraint(equalTo: self.trailingAnchor).isActive = true
        label.bottomAnchor.constraint(equalTo: self.bottomAnchor).isActive = true
        label.sizeToFit()
    }
}

Answer 1

在this的帮助下发布后，我能够以编程方式创建动态 UICollectionViewCell:

设置 UICollectionView 布局的estimatedItemSize，如下所示:

if let flowLayout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout {
    flowLayout.estimatedItemSize = CGSize(width: 1, height: 1)
}

在 UICollectionViewCell 的 contentView 中添加 UIControls

self.contentView.translatesAutoresizingMaskIntoConstraints = false

let screenWidth = UIScreen.main.bounds.size.width

contentView.addSubview(msgLabel)

[
    msgLabel.leadingAnchor.constraint(equalTo: contentView.leadingAnchor, constant: 8),
    msgLabel.topAnchor.constraint(equalTo: contentView.topAnchor, constant: 8),
    msgLabel.trailingAnchor.constraint(equalTo: contentView.trailingAnchor, constant: -8),
    msgLabel.bottomAnchor.constraint(equalTo: contentView.bottomAnchor, constant: -8),
    msgLabel.widthAnchor.constraint(equalToConstant: screenWidth - 16)
    ].forEach{ $0.isActive = true }

Set numberOfLines of UILabel to 0