在视图控制器演示期间制作collectionView布局动画

import UIKit

class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
    private let reuseIdentifier = "Cell"
    private var collectionView: UICollectionView!
    private var data = [Int]()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建UICollectionViewFlowLayout实例
        let layout = UICollectionViewFlowLayout()
        layout.scrollDirection = .vertical
        layout.minimumInteritemSpacing = 10
        layout.minimumLineSpacing = 10
        
        // 创建UICollectionView实例
        collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: layout)
        collectionView.dataSource = self
        collectionView.delegate = self
        collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: reuseIdentifier)
        collectionView.backgroundColor = .white
        view.addSubview(collectionView)
        
        // 添加一些示例数据
        for i in 0..<10 {
            data.append(i)
        }
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        
        // 刷新collectionView数据
        collectionView.reloadData()
        
        // 执行布局动画
        animateCollectionView()
    }
    
    func animateCollectionView() {
        let cells = collectionView.visibleCells
        let collectionViewHeight = collectionView.bounds.size.height
        
        for (index, cell) in cells.enumerated() {
            cell.transform = CGAffineTransform(translationX: 0, y: collectionViewHeight)
            cell.alpha = 0
            
            UIView.animate(withDuration: 0.5, delay: 0.1 * Double(index), options: .curveEaseInOut, animations: {
                cell.transform = CGAffineTransform.identity
                cell.alpha = 1
            }, completion: nil)
        }
    }
    
    // MARK: - UICollectionViewDataSource
    
    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 1
    }
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return data.count
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath)
        cell.backgroundColor = .blue
        
        return cell
    }
    
    // MARK: - UICollectionViewDelegateFlowLayout
    
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize(width: 100, height: 100)
    }
}