ios - UICollectionView - 重新打开应用程序时未正确重绘

Question

出于某种原因，我的 Collection View 代码在启动模拟器时按预期工作，但是当我按下主页按钮关闭应用程序然后重新打开它时，3 列在右侧折叠为一列。我在 Storyboard 中唯一拥有的就是 View 。一切都是通过代码完成的。 Xcode 11.1/Swift 5。

这是第一次打开时的样子:

在重新打开时:

这是所有的代码。

class Online: UIViewController {

    weak var collectionView: UICollectionView!
    var onlineArray = [[String:AnyObject]]()

    override func viewDidLoad() {
        super.viewDidLoad()

        let collectionView = UICollectionView(frame: .zero, collectionViewLayout: UICollectionViewFlowLayout())
        collectionView.translatesAutoresizingMaskIntoConstraints = false

        self.view.addSubview(collectionView)

        NSLayoutConstraint.activate([
            self.view.topAnchor.constraint(equalTo: collectionView.topAnchor),
            self.view.bottomAnchor.constraint(equalTo: collectionView.bottomAnchor),
            self.view.leadingAnchor.constraint(equalTo: collectionView.leadingAnchor),
            self.view.trailingAnchor.constraint(equalTo: collectionView.trailingAnchor),
        ])

        self.collectionView = collectionView

        self.collectionView.dataSource = self
        self.collectionView.delegate = self
        self.collectionView.register(Cell.self, forCellWithReuseIdentifier: Cell.identifier)
        self.collectionView.alwaysBounceVertical = true
    }

}

extension Online: UICollectionViewDataSource {

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 10
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: Cell.identifier, for: indexPath) as! Cell

        cell.textLabel1.text = "A"
        cell.textLabel2.text = "B"
        cell.textLabel3.text = "C"

        cell.textLabel1.backgroundColor = .orange
        cell.textLabel2.backgroundColor = .blue
        cell.textLabel3.backgroundColor = .green

        return cell
    }

}

extension Online: UICollectionViewDelegateFlowLayout {

    func collectionView(_ collectionView: UICollectionView,
                        layout collectionViewLayout: UICollectionViewLayout,
                        sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize(width: collectionView.bounds.width, height: 30)
    }

    func collectionView(_ collectionView: UICollectionView,
                        layout collectionViewLayout: UICollectionViewLayout,
                        insetForSectionAt section: Int) -> UIEdgeInsets {
        return UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0) //.zero
    }

    func collectionView(_ collectionView: UICollectionView,
                        layout collectionViewLayout: UICollectionViewLayout,
                        minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        return 0
    }

    func collectionView(_ collectionView: UICollectionView,
                        layout collectionViewLayout: UICollectionViewLayout,
                        minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 0
    }

}

class Cell: UICollectionViewCell {

    static var identifier: String = "Cell"

    weak var textLabel1: UILabel!
    weak var textLabel2: UILabel!
    weak var textLabel3: UILabel!

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

        let width = self.contentView.frame.size.width

        let textLabel1 = UILabel(frame: CGRect(x: 10, y: 0, width: 50, height: 20))
        let textLabel2 = UILabel(frame: CGRect(x: width/3, y: 0, width: 50, height: 20))
        let textLabel3 = UILabel(frame: CGRect(x: (width/3)*2, y: 0, width: 50, height: 20))

        textLabel1.translatesAutoresizingMaskIntoConstraints = false
        textLabel2.translatesAutoresizingMaskIntoConstraints = false
        textLabel3.translatesAutoresizingMaskIntoConstraints = false

        self.contentView.addSubview(textLabel1)
        self.contentView.addSubview(textLabel2)
        self.contentView.addSubview(textLabel3)

        self.textLabel1 = textLabel1
        self.textLabel2 = textLabel2
        self.textLabel3 = textLabel3
        self.reset()
    }

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

    override func prepareForReuse() {
        super.prepareForReuse()
        self.reset()
    }

    func reset() {
        self.textLabel1.textAlignment = .left
        self.textLabel2.textAlignment = .center
        self.textLabel3.textAlignment = .right
    }

}

Answer 1

所以我想我会回答我自己的问题。

translatesAutoresizingMaskIntoConstraints 应该是 true 而不是 false。

    textLabel1.translatesAutoresizingMaskIntoConstraints = true
    textLabel2.translatesAutoresizingMaskIntoConstraints = true
    textLabel3.translatesAutoresizingMaskIntoConstraints = true