创建自定义的CollectionViewCell

import UIKit
 class UserCustomCollectionViewController: UIViewController, UICollectionViewDelegate,     UICollectionViewDataSource {`

    var collectionView:UICollectionView!

    override funcviewDidLoad() {

        super.viewDidLoad()

        let layout =CustomLayout()

        collectionView=UICollectionView(frame:CGRect(x:0, y:100, width:375, height:500), collectionViewLayout: layout)

        collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "123")

        collectionView.delegate = self

        collectionView.dataSource = self

        self.view.addSubview(collectionView)

    }


    // - MARK: - UICollectionDelegate

    funccollectionView(_collectionView:UICollectionView, numberOfItemsInSection section:Int) ->Int{

        return 10

    }

    funccollectionView(_collectionView:UICollectionView, cellForItemAt indexPath:IndexPath) ->UICollectionViewCell{

        letcell = collectionView.dequeueReusableCell(withReuseIdentifier:"123", for: indexPath)


        if indexPath.row%2==0{

            cell.backgroundColor=  colorLiteral(red: 0.8784313725, green: 0.07058823529, blue: 0.07058823529, alpha: 1)

        }else{

            cell.backgroundColor=  colorLiteral(red: 0.01316650119, green: 0.1738643348, blue: 0.8993083835, alpha: 1)

        }

        return cell
    }

}

class CustomLayout: UICollectionViewLayout {`

    // 内容区域总大小，不是可见区域

    overridevarcollectionViewContentSize:CGSize{

        let width = collectionView!.bounds.size.width - collectionView!.contentInset.left

            -collectionView!.contentInset.right

        letheight =CGFloat((collectionView!.numberOfItems(inSection:0) +1) /3)

            * (width /3*2)

        returnCGSize(width: width, height: height)

    }

    // 所有单元格位置属性

    overridefunclayoutAttributesForElements(in rect:CGRect)

        -> [UICollectionViewLayoutAttributes]? {

            varattributesArray = [UICollectionViewLayoutAttributes]()

            letcellCount =self.collectionView!.numberOfItems(inSection:0)

            foriin0..

                letindexPath =  IndexPath(item:i, section:0)

                letattributes =  self.layoutAttributesForItem(at: indexPath)

                attributesArray.append(attributes!)

            }

            returnattributesArray

    }

    // 这个方法返回每个单元格的位置和大小

    override funclayoutAttributesForItem(at indexPath:IndexPath)

        ->UICollectionViewLayoutAttributes? {

            //当前单元格布局属性

            let attribute =  UICollectionViewLayoutAttributes(forCellWith:indexPath)



            //单元格边长

            let largeCellSide =collectionViewContentSize.width/3*2

            let smallCellSide =collectionViewContentSize.width/3

            //当前行数，每行显示3个图片，1大2小

            let line:Int=  indexPath.item/3

            //当前行的Y坐标

            letlineOriginY =  largeCellSide *CGFloat(line)

            //右侧单元格X坐标，这里按左右对齐，所以中间空隙大

            letrightLargeX =collectionViewContentSize.width- largeCellSide

            letrightSmallX =collectionViewContentSize.width- smallCellSide

            // 每行2个图片，2行循环一次，一共6种位置

            if (indexPath.item%6==0) {

                attribute.frame=CGRect(x:0, y:lineOriginY, width:largeCellSide,

                                         height:largeCellSide)

            }else if(indexPath.item%6==1) {

                attribute.frame=CGRect(x:rightSmallX, y:lineOriginY, width:smallCellSide,

                                         height:smallCellSide)

            }else if(indexPath.item%6==2) {

                attribute.frame=CGRect(x:rightSmallX,

                                         y:lineOriginY + smallCellSide,

                                         width:smallCellSide, height:smallCellSide)

            }elseif(indexPath.item%6==3) {

                attribute.frame=CGRect(x:0, y:lineOriginY, width:smallCellSide,

                                         height:smallCellSide )

            }elseif(indexPath.item%6==4) {

                attribute.frame=CGRect(x:0,

                                         y:lineOriginY + smallCellSide,

                                         width:smallCellSide, height:smallCellSide)

            }else if(indexPath.item%6==5) {

                attribute.frame=CGRect(x:rightLargeX, y:lineOriginY,

                                         width:largeCellSide,

                                         height:largeCellSide)

            }

            return attribute
    }
}