細胞沒有出現在UICollectionView

Question

我不明白爲什麼我的細胞沒有顯示：

class MenuBar: UIView, UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout { 

    let cellId = "pouet" 

    lazy var customCollectionView : UICollectionView = { 
     let layout = UICollectionViewLayout() 
     let cv = UICollectionView(frame: .zero, collectionViewLayout: layout) 
     cv.backgroundColor = UIColor.gray 
     cv.dataSource = self 
     cv.delegate = self 

     return cv 
    }() 

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

     customCollectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: cellId) 
     addSubview(customCollectionView) 
     addConstraintsWithFormat(format: "H:|[v0]|", views: customCollectionView) 
     addConstraintsWithFormat(format: "V:|[v0]|", views: customCollectionView) 
    } 

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int { 
     return 4 
    } 

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell { 
     let cell = customCollectionView.dequeueReusableCell(withReuseIdentifier: cellId, for: indexPath) 
     print("test") 

     return cell 
    } 

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

現在我print("test")沒有顯示任何，這意味着該方法實際上是不叫的吧？那麼，什麼是錯的？

Answer 1

更改這行代碼：

let layout = UICollectionViewLayout() 

要：

let layout = UICollectionViewFlowLayout() 

UICollectionViewLayout是抽象類，你不能直接使用它。