ios - CollectionView 显示黑屏

Question

您好，我正在尝试以编程方式创建一个 collectionView。我改变了它的颜色，它仍然显示默认颜色。而且代码并没有真正起作用。我很确定它是 appDelegate 中的问题，但无法弄清楚。这是我在 appDelegate 中的应用方法:

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    // Create one
    window = UIWindow(frame: UIScreen.main.bounds)

    //Shows the window and makes it the key window.
    window?.makeKeyAndVisible()

    //Must give a layout to it by default
    let flowLayout = UICollectionViewFlowLayout()
    let customCollectionViewController = UICollectionViewController(collectionViewLayout: flowLayout)
    window?.rootViewController = UINavigationController(rootViewController: customCollectionViewController)
    return true
}

这是 CollectionViewController 代码

class CustomCollectionViewController: UICollectionViewController, UICollectionViewDelegateFlowLayout {

let identifier = "customCell"
override func viewDidLoad() {
    super.viewDidLoad()
    collectionView?.backgroundColor = UIColor.gray
    collectionView?.register(CustomCell.self, forCellWithReuseIdentifier: identifier)
}


override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let customCell = collectionView.dequeueReusableCell(withReuseIdentifier: identifier, for: indexPath)
    return customCell
}



override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return 3
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    return CGSize(width: view.frame.width, height: 100)
}

class CustomCell: UICollectionViewCell{
   override init(frame: CGRect) {
    super.init(frame: frame)
    setupViews()
}

let nameLabel: UILabel = {
    let label = UILabel()
    label.text = "Hello World"

    label.translatesAutoresizingMaskIntoConstraints = false
    return label

}()

func setupViews(){
    backgroundColor = UIColor.white
    addSubview(nameLabel)

    addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|v0|", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": nameLabel]))
    addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|v0|", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": nameLabel]))
}

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

我正在使用 Xcode 8.2.1

Answer 1

您没有使用您的 CustomCollectionViewController，您使用的是 UICollectionViewController。

替换

    let customCollectionViewController = UICollectionViewController(collectionViewLayout: flowLayout)

与

    let customCollectionViewController = CustomCollectionViewController(collectionViewLayout: flowLayout)

您在单元格中的约束代码也导致我崩溃，但如果您只是评论这些行，您应该会看到 Collection View 出现。