Swift4下做动态九宫格布局

类似朋友圈九宫格布局，一张，两张，四张等情况时，用imageView来添加，约束非常繁琐，现在有一种简单的布局方法：collectionView，然后根据图片个数，来定义collectionView的layout和collectionView的高度：

var images = [String](){
        didSet{
            
            if images.count == 0 {
                imageBackViewHeight.constant = 0
            }
            if images.count == 1 {
                
                let height = screenwidth - 30
                
                imageBackViewHeight.constant = height
                collectionLayout.itemSize = CGSize(width: height, height: height)
                collectionLayout.minimumLineSpacing = 0
                collectionLayout.minimumInteritemSpacing = 0
                
            }
            
            if images.count == 2 {
                let height = (screenwidth - 3 - 30)/2
                imageBackViewHeight.constant = height
                collectionLayout.itemSize = CGSize(width: height, height: height)
                collectionLayout.minimumLineSpacing = 0
                collectionLayout.minimumInteritemSpacing = 3
            }
            
            if images.count == 3 {
                let height = (screenwidth - 6 - 30)/3
                imageBackViewHeight.constant = height
                collectionLayout.itemSize = CGSize(width: height, height: height)
                collectionLayout.minimumLineSpacing = 0
                collectionLayout.minimumInteritemSpacing = 3
            }
            if images.count == 4 {
                
                let height = (screenwidth - 6 - 30)/2
                
                imageBackViewHeight.constant = height * 2 + 3
                collectionLayout.itemSize = CGSize(width: height, height: height)
                collectionLayout.minimumLineSpacing = 3
                collectionLayout.minimumInteritemSpacing = 3
            }
            if images.count > 4 && images.count < 7 {
                
                let height = (screenwidth - 6 - 30)/3
                
                imageBackViewHeight.constant = height * 2 + 3
                
                collectionLayout.itemSize = CGSize(width: height, height: height)
                collectionLayout.minimumLineSpacing = 3
                collectionLayout.minimumInteritemSpacing = 3
            }

            if images.count >= 7 {
                let height = (screenwidth - 6 - 30)/3
                
                imageBackViewHeight.constant = height * 3 + 6
                
                collectionLayout.itemSize = CGSize(width: height, height: height)
                collectionLayout.minimumLineSpacing = 3
                collectionLayout.minimumInteritemSpacing = 3
            }
        
            
            collectionView.reloadData()
        }
    }

然后利用回调，把想要的数据回调过来，比如点击图片放大什么的：

//cell里的collectionView
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        
        if let tapImageBlock = self.tapImageBlock{
            tapImageBlock(indexPath.item, self.images[indexPath.item])
        }
    }

//列表的tableview代理
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        
        let cell = tableView.dequeueReusableCell(withIdentifier: "QLHomeTrendsCell", for: indexPath) as! QLHomeTrendsCell

        cell.images = self.dataArr[indexPath.row]
        
        cell.tapImageBlock = {(index, imageUrl) in
            print("点击了第\(index)张图片，图片链接是\(imageUrl)")
        }

        return cell
    }

完整代码在这