Jul-29-2019 15-41-54.gif

UICollectionView主要有以下几个难点

1. UICollectionViewDelegateFlowLayout

使用系统的layout

 let collectionLayout = UICollectionViewFlowLayout.init()
 let rect = CGRect(x: 0, y: 0, width: screenW, height: screenH)
 let collectionView = UICollectionView(frame: rect, collectionViewLayout: collectionLayout)

2. 方法的运用

必须实现方法

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 15
    }    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView .dequeueReusableCell(withReuseIdentifier: "UICollectionViewCell", for: indexPath)
        cell.backgroundColor = kColor(red: 53, green: 49, blue: 59)
        cell.layer.cornerRadius = 5;
        cell.layer.masksToBounds = true
        return cell
    }

header和footer 设置

    //   MARK: - 设定header和footer的方法，根据kind不同进行不同的判断即可
    func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
        if kind == UICollectionView.elementKindSectionHeader{
            let headerV = collectionView .dequeueReusableSupplementaryView(ofKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: "headerIdentifier", for: indexPath)
            headerV.backgroundColor = armColor()
            return headerV
        }else if kind == UICollectionView.elementKindSectionFooter{
            let footerV = collectionView .dequeueReusableSupplementaryView(ofKind: UICollectionView.elementKindSectionFooter, withReuseIdentifier: "footIdentifier", for: indexPath)
            footerV.backgroundColor = armColor()
            return footerV
        }
        return UICollectionReusableView.init()
    }
    
    //    MARK: - headerView 高
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
        return CGSize (width: screenW, height: 100)
    }
    
    //    MARK: - footerView 高
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForFooterInSection section: Int) -> CGSize {
        return CGSize (width: screenW, height: 100)
    }

item Size

    //    MARK: - item Size
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        let itemW = (screenW-50)/3
        return CGSize(width: itemW, height: itemW)
    }

边框距离

    //     MARK: - 边框距离
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
        return  UIEdgeInsets(top: 10, left: 10, bottom: 10, right: 10)
    }

行最小间距

    //    MARK: - 行最小间距
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 15
    }

列最小间距

    //    MARK: - 列最小间距
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        return 5
    }

item点击事件

    //    MARK: - item 点击
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        //        let cell = collectionView .cellForItem(at: indexPath)
        //        cell?.backgroundColor = armColor();
        
    }

item 高亮处理

    //    MARK: - 是否高亮
    func collectionView(_ collectionView: UICollectionView, shouldHighlightItemAt indexPath: IndexPath) -> Bool{
        return true
    }
    
    //    MARK: - 高亮颜色
    func collectionView(_ collectionView: UICollectionView, didHighlightItemAt indexPath: IndexPath){
        let cell = collectionView .cellForItem(at: indexPath)
        cell?.backgroundColor = armColor()
    }
    
    //    MARK: - 取消长按颜色
    func collectionView(_ collectionView: UICollectionView, didUnhighlightItemAt indexPath: IndexPath){
        let cell = collectionView .cellForItem(at: indexPath)
        cell?.backgroundColor = kColor(red: 53, green: 49, blue: 59)
    }
    
    func armColor()->UIColor{
        let red = CGFloat(arc4random()%256)/255.0
        let green = CGFloat(arc4random()%256)/255.0
        let blue = CGFloat(arc4random()%256)/255.0
        print("red:\(red),green:\(green),blue:\(blue)")
        return UIColor(red: red, green: green, blue: blue, alpha: 1.0)
    }