如何使用垂直滚动一次显示一个collectionView单元格

import UIKit

class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource {
    @IBOutlet weak var collectionView: UICollectionView!
    
    let data = ["Cell 1", "Cell 2", "Cell 3", "Cell 4", "Cell 5"] // 数据源数组
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        collectionView.delegate = self
        collectionView.dataSource = self
        
        let layout = UICollectionViewFlowLayout()
        layout.scrollDirection = .vertical
        collectionView.collectionViewLayout = layout
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        
        // 滚动到第一个单元格
        collectionView.setContentOffset(CGPoint(x: 0, y: 0), animated: false)
    }
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return data.count
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath)
        cell.backgroundColor = UIColor.lightGray
        cell.textLabel?.text = data[indexPath.row]
        return cell
    }
}