如何设置UICollectionViewCell大小

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    let width = collectionView.bounds.width / 2 // 设置单元格宽度为集合视图宽度的一半
    let height = 100 // 设置单元格高度为100
    return CGSize(width: width, height: height)
}

let layout = UICollectionViewFlowLayout()
layout.itemSize = CGSize(width: 100, height: 100) // 设置单元格宽度和高度为100
collectionView.collectionViewLayout = layout

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    // 根据indexPath获取对应的单元格
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! CustomCell
    
    // 根据indexPath设置不同的单元格大小
    if indexPath.row % 2 == 0 {
        cell.frame.size = CGSize(width: 100, height: 100)
    } else {
        cell.frame.size = CGSize(width: 200, height: 200)
    }
    
    return cell
}