UICollectionViewLayout方法永远不会被调用

class CustomCollectionViewLayout: UICollectionViewLayout {
    override func prepare() {
        super.prepare()
        // 准备布局
    }

    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        // 返回布局属性
        return nil
    }

    override func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
        // 返回单个项目的布局属性
        return nil
    }
}

class ViewController: UIViewController, UICollectionViewDataSource {
    var collectionView: UICollectionView!

    override func viewDidLoad() {
        super.viewDidLoad()
        
        let layout = CustomCollectionViewLayout()
        collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: layout)
        collectionView.dataSource = self
        view.addSubview(collectionView)
        
        // 注册cell等
    }

    // 数据源方法
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 10 // 示例数据
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellIdentifier", for: indexPath)
        // 配置cell
        return cell
    }
}