ios - 未调用 UICollectionView cellForItem

Question

我正在一个基本的 ViewController 中实现一个 UICollectionView (collectionView)我的 Collection View 必须像 numbersofItemInSection 代码中那样检索 5 个单元格。显示 CollectionView 并调用 numbersofItemInSection 函数，但未调用 cellForItemAt 函数，因此 Collection View 为空。

import UIKit


private let reuseIdentifier = "Cell"



class TestViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate{

    lazy var collectionView : UICollectionView = {
        let layout = UICollectionViewFlowLayout()
        let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
        cv.translatesAutoresizingMaskIntoConstraints = false
        cv.delegate = self
        cv.dataSource = self
        return cv
    }()

    override func viewDidLoad() {
        super.viewDidLoad()

        // Register cell classes
        self.collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: reuseIdentifier)

        collectionView.backgroundColor = .white
        navigationItem.title = "test"

        setupViews()
    }

    func setupViews(){
        view.addSubview(collectionView)

        collectionView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
        collectionView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
        collectionView.heightAnchor.constraint(equalToConstant: 60).isActive = true
        collectionView.topAnchor.constraint(equalTo: topLayoutGuide.bottomAnchor).isActive = true
    }

     func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 5
    }

     func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath)
        // Configure the cell

        cell.backgroundColor = .red

        return cell
    }


}

Answer 1

是你的collectionView的高度或者collectionView的frame问题，那么你需要给collectionView设置合适的高度。

或

试试这个

     override func viewDidLoad() {
                super.viewDidLoad()
                navigationItem.title = "test"

                setupViews()
                collectionView.backgroundColor = .white
                self.collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: reuseIdentifier) 
// remove this line if you not use xib

            }