import UIKit

class ImageCell: UICollectionViewCell {
    let imageView = UIImageView()
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        
        // 设置imageView的布局和样式
        imageView.contentMode = .scaleAspectFill
        imageView.clipsToBounds = true
        imageView.frame = contentView.bounds
        contentView.addSubview(imageView)
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
    let images = [UIImage(named: "image1"), UIImage(named: "image2"), UIImage(named: "image3"), UIImage(named: "image4"), UIImage(named: "image5"), UIImage(named: "image6")]
    let collectionView = UICollectionView(frame: .zero, collectionViewLayout: UICollectionViewFlowLayout())
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 设置collectionView的布局和样式
        collectionView.dataSource = self
        collectionView.delegate = self
        collectionView.register(ImageCell.self, forCellWithReuseIdentifier: "ImageCell")
        collectionView.backgroundColor = .white
        view.addSubview(collectionView)
        
        // 设置collectionView的约束
        collectionView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            collectionView.topAnchor.constraint(equalTo: view.topAnchor),
            collectionView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            collectionView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            collectionView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
        ])
    }
    
    // MARK: - UICollectionViewDataSource
    
    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 1
    }
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return images.count
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "ImageCell", for: indexPath) as! ImageCell
        cell.imageView.image = images[indexPath.item]
        return cell
    }
    
    // MARK: - UICollectionViewDelegateFlowLayout
    
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        let width = collectionView.bounds.width / 4 - 10 // 每行显示4张图像，减去间距
        let height = width
        return CGSize(width: width, height: height)
    }
}