Swift UICollectionView 自适应cell、 section圆角、cell选中效果

效果图：

效果图.png

代码

import UIKit

let SCREEN_WIDTH = UIScreen.main.bounds.size.width
let SCREEN_HEIGHT = UIScreen.main.bounds.size.height

class CYNewPlayViewController: UIViewController {

    private var collectionView: UICollectionView!
    private lazy var indicatorView = UIView()
    private var dataList: [String] = []

    override func viewDidLoad() {
        super.viewDidLoad()
        dataList = ["cyan1","cyan2","cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3cyan3","cyan4","cyan5","cyan6"]
        initialAppearance()
    }

    private func initialAppearance() {
        view.backgroundColor = .white
        let layout = MineDecorationFlowlayout(with: MineDecorationView.self)
        layout.dc_delegate = self
        layout.minimumLineSpacing = 0
        layout.minimumInteritemSpacing = 0
        layout.estimatedItemSize = CGSize(width: UIScreen.main.bounds.size.width, height: 100)

        let collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
        collectionView.delegate = self
        collectionView.dataSource = self
        collectionView.register(CYCollectionViewCell.self, forCellWithReuseIdentifier: "CYCollectionViewCell")
        collectionView.backgroundColor = .gray
        collectionView.showsVerticalScrollIndicator = false
        collectionView.showsHorizontalScrollIndicator = false
        view.addSubview(collectionView)
        self.collectionView = collectionView

        collectionView.snp.makeConstraints { (make) in
            make.edges.equalToSuperview()
        }

    }
}
// MARK: - UICollectionViewDelegate
extension CYNewPlayViewController: UICollectionViewDelegate, UICollectionViewDataSource, MineDecorationFlowlayoutDelegate {

    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 3
    }

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        switch section {
        case 0: return 1
        default: return dataList.count
        }
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "CYCollectionViewCell", for: indexPath) as! CYCollectionViewCell
        let title = dataList[indexPath.item]
        cell.titleLabel.text = title
        // 设置圆角样式
        if indexPath.section == 0 {
            cell.locationType = .all
        } else {
            switch indexPath.item {
            case 0: cell.locationType = .top
            case dataList.count - 1: cell.locationType = .bottom
            default: cell.locationType = .middle
            }
        }
        return cell
    }

    func layout(_ layout: MineDecorationFlowlayout, decorationImageAt section: Int) -> String {
        return ""
    }

    func layout(_ layout: MineDecorationFlowlayout, decorationImageAt indexPath: IndexPath) -> String {
        return ""
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
        return UIEdgeInsets(top: 15, left: 0, bottom: 0, right: 0)
    }
}

// MARK: - cell
class CYCollectionViewCell: UICollectionViewCell {
    ///  cell圆角位置
    enum CYCellLocationType {
        case top // 头部圆角
        case middle // 无圆角
        case bottom // 底部圆角
        case all // 全圆角
    }

    var bgView = UIView()
    var titleLabel = UILabel()
    var locationType: CYCellLocationType = .middle {
        didSet {
            self.setNeedsLayout()
            self.layoutIfNeeded()
        }
    }
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
        initialAppearance()
    }

    override func layoutSubviews() {
        super.layoutSubviews()
        contentView.setNeedsLayout()
        contentView.layoutIfNeeded()
        reloadBgView(locationType)
    }

    private func reloadBgView(_ type: CYCellLocationType) {
        let size = CGSize(width: 10, height: 10)
        var corners: UIRectCorner = []
        switch type {
        case .top: corners = [.topLeft, .topRight]
        case .bottom: corners = [.bottomLeft, .bottomRight]
        case .all: corners = [.allCorners]
        default:
            break
        }
        //设置mask
        let mask = bgView.viewMaskWithBounds(bounds: bgView.bounds, corners: corners, cornerRadii: size)
        bgView.layer.mask = mask
    }

    func initialAppearance() {
        bgView.backgroundColor = UIColor.systemGray
        bgView.isHidden = true
        self.contentView.addSubview(bgView)

        titleLabel.font = UIFont.systemFont(ofSize: 16)
        titleLabel.numberOfLines = 0
        self.contentView.addSubview(titleLabel)

        bgView.snp.makeConstraints { (make) in
            make.left.equalToSuperview().offset(12)
            make.right.equalToSuperview().offset(-12)
            make.top.bottom.equalToSuperview()
        }

        titleLabel.snp.makeConstraints { (make) in
            make.left.top.equalToSuperview().offset(15)
            make.right.equalToSuperview().offset(-15)
            make.bottom.equalToSuperview().offset(-15)
        }
    }

    override func preferredLayoutAttributesFitting(_ layoutAttributes: UICollectionViewLayoutAttributes) -> UICollectionViewLayoutAttributes {
        self.setNeedsLayout()
        self.layoutIfNeeded()
        let size = self.contentView.systemLayoutSizeFitting(layoutAttributes.size)
        var cellFrame = layoutAttributes.frame
        cellFrame.size.height = size.height
        layoutAttributes.frame = cellFrame
        return layoutAttributes
    }

    // MARK: - 选中效果相关
    private var isSelect: Bool = false
    private var isHighlight: Bool = false

    override var isSelected: Bool {
        set {
            self.isSelect = newValue
            self.bgView.isHidden = !newValue
        }
        get {
            return self.isSelect
        }
    }

    override var isHighlighted: Bool {
        set {
            self.isHighlight = newValue
            self.bgView.isHidden = !newValue
        }
        get {
            return self.isHighlight
        }
    }
}

// MARK: - MineDecorationView
class MineDecorationView: UICollectionReusableView {
    lazy var imageView = UIImageView()

    override init(frame: CGRect) {
        super.init(frame: frame)
        imageView.layer.cornerRadius = 10
        imageView.backgroundColor = .white
        addSubview(imageView)
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func apply(_ layoutAttributes: UICollectionViewLayoutAttributes) {
        super.apply(layoutAttributes)
        let frame = CGRect(x: 12, y: 0, width: layoutAttributes.bounds.width - 24, height: layoutAttributes.bounds.height)
        imageView.frame = frame
        guard let attributes = layoutAttributes as? MineDecorationAttributes, let imageName = attributes.imageName, !imageName.isEmpty else { return }
        imageView.image = UIImage(named: imageName)
    }
}

// MARK: - MineDecorationAttributes
class MineDecorationAttributes: UICollectionViewLayoutAttributes {
    var imageName: String?
}

// MARK: - MineDecorationFlowlayout
protocol MineDecorationFlowlayoutDelegate: UICollectionViewDelegateFlowLayout {
    func layout(_ layout: MineDecorationFlowlayout, decorationImageAt section: Int) -> String
    func layout(_ layout: MineDecorationFlowlayout, decorationImageAt indexPath: IndexPath) -> String
}

class MineDecorationFlowlayout: UICollectionViewFlowLayout {
    let decorationViewKind: String
    let viewType: AnyClass
    var itemsAttribute: [UICollectionViewLayoutAttributes] = []
    weak var dc_delegate: MineDecorationFlowlayoutDelegate?

    init(with viewKind: UICollectionReusableView.Type) {
        decorationViewKind = String(describing: viewKind)
        viewType = viewKind
        super.init()
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func prepare() {
        super.prepare()
        self.register(viewType, forDecorationViewOfKind: decorationViewKind)

        self.itemsAttribute.removeAll()
        let sections = self.collectionView?.numberOfSections ?? 0

        // 给section添加一张背景图片
        for i in 0.. 0 {
                let firstItem = self.layoutAttributesForItem(at: IndexPath(item: 0, section: i))
                let lastItem = self.layoutAttributesForItem(at: IndexPath(item: (count - 1), section: i))
                let height = lastItem!.frame.maxY - firstItem!.frame.minY
                attribute.frame = CGRect(x: 0, y: firstItem!.frame.minY, width: self.collectionView!.frame.size.width, height: height)
                self.itemsAttribute.append(attribute)
            }
        }
    }

    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        var attributes = super.layoutAttributesForElements(in: rect)

        for attribute in self.itemsAttribute {
            if rect.intersects(attribute.frame) {
                attributes?.append(attribute)
            }
        }
        return attributes
    }
}


extension UIView {
    /**
     let size = CGSize(width: 3, height: 3)
     //设置layer
     let layer = self.showImageV.viewLayerWithBounds(bounds: self.showImageV.bounds, corners: [.topLeft, .topRight], cornerRadii: size, color: UIColor.clear)
     //设置mask
     let mask = self.showImageV.viewMaskWithBounds(bounds: self.showImageV.bounds, corners: [.topLeft, .topRight], cornerRadii: size)
     self.showImageV.layer.addSublayer(layer)
     self.showImageV.layer.mask = mask
     *注 在使用masnory 的时候 需要在layoutSubviews 方法后增加
     contentView.setNeedsLayout()
     contentView.layoutIfNeeded()
     防止bounds为空
     */
    func viewLayerWithBounds(bounds: CGRect,corners: UIRectCorner,cornerRadii : CGSize,color: UIColor?) -> CALayer {
        let maskPath3 = UIBezierPath.init(roundedRect: bounds, byRoundingCorners: corners, cornerRadii: cornerRadii)
        let borderLayer3 = CAShapeLayer.init()
        borderLayer3.frame = bounds
        borderLayer3.path = maskPath3.cgPath
        if color == nil {
            borderLayer3.strokeColor = UIColor.init(red: 228.0 / 255, green: 228.0 / 255, blue: 228.0 / 255, alpha: 1).cgColor
        }else {
            borderLayer3.strokeColor = color?.cgColor
        }
        borderLayer3.fillColor = UIColor.clear.cgColor
        borderLayer3.lineWidth = 2.0
        borderLayer3.lineDashPattern = [4,2]
        return borderLayer3
    }

    func viewMaskWithBounds(bounds: CGRect,corners: UIRectCorner,cornerRadii : CGSize) -> CALayer {
        let maskPath3 = UIBezierPath.init(roundedRect: bounds, byRoundingCorners: corners, cornerRadii: cornerRadii)
        let maskLayer3 = CAShapeLayer()
        maskLayer3.frame = bounds
        maskLayer3.path = maskPath3.cgPath
        return maskLayer3
    }
}