image.png

1、绘制刻度尺子的layer

class YXScaleLayer: CAShapeLayer {
    var maxHeight = 40.0
    var minHeight = 20.0
    private(set) var dataArr: [DataEntity] = []
    private let bezierPath = UIBezierPath()
    private(set) var space: CGFloat = 8
    
    override func layoutSublayers() {
        super.layoutSublayers()
        let y = bounds.height
        for item in dataArr {
            bezierPath.move(to: CGPoint(x: item.posX, y: y))
            let posY = item.isLong ? (y-maxHeight) : (y-minHeight)
            bezierPath.addLine(to: CGPoint(x: item.posX, y: posY))
        }
        self.path = bezierPath.cgPath
    }
    
    var longItems: [DataEntity] {
//        dataArr.filter { $0.index % 2 == 0 }
        dataArr.filter { $0.isLong }
    }
}
extension YXScaleLayer {

    func setData(_ arr: [Int], space: CGFloat = 20) {
        self.space = space
        var posX = lineWidth/2
        var index = 0
        for long in arr {
            for _ in 0..<long {
                dataArr.append(DataEntity(index: index, posX: posX))
                posX += (space+lineWidth)
                index += 1
            }
            dataArr.append(DataEntity(index: index, posX: posX, isLong: true))
            posX += (space+lineWidth)
            index += 1
        }
        var rect = frame
        rect.size.width = posX - space
        frame = rect
    }
    
}

extension YXScaleLayer {
    struct DataEntity {
        var index: Int
        var posX: CGFloat
        var isLong = false
    }
}

2、指示计及滑动容器逻辑

class YXRulerView: UIView {
    
    private let contentView = UIScrollView()
    private let scaleLayer = YXScaleLayer()
    private let indicatorLayer = CALayer()
    private let titleContentView = UIView()
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        translatesAutoresizingMaskIntoConstraints = false
        
        scaleLayer.lineWidth = 2.0
        scaleLayer.strokeColor = UIColor.lightGray.cgColor
        contentView.layer.addSublayer(scaleLayer)
        contentView.showsHorizontalScrollIndicator = false
        contentView.delegate = self
        contentView.decelerationRate = .init(rawValue: 0.01) //降低手指离开屏幕后scrollView的滚动速度
        addSubview(contentView)
        indicatorLayer.backgroundColor = UIColor.red.cgColor
        layer.addSublayer(indicatorLayer)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func layoutSubviews() {
        super.layoutSubviews()
        contentView.frame = bounds
        
        let contentW = scaleLayer.frame.width
        scaleLayer.frame = CGRect(x: 0, y: 0, width: contentW, height: 60)
        contentView.contentSize = .init(width: contentW, height: bounds.height)
        contentView.contentInset = UIEdgeInsets(top: 0, left: bounds.width/2, bottom: 0, right: bounds.width/2)
        
        titleContentView.frame = CGRect(x: 0, y: 70, width: contentW, height: 20)
        indicatorLayer.frame = CGRect(x: bounds.width/2, y: 0, width: 1, height: bounds.height)
    }
    
    func setData(_ arr: [Int]) {
        scaleLayer.setData(arr)
        
        createTitles()
        DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
            self.handleScrollEnd()
        }
    }
    
    private func createTitles() {
        titleContentView.backgroundColor = .brown.withAlphaComponent(0.3)
        contentView.addSubview(titleContentView)
        let longs = scaleLayer.longItems
        
        for long in longs {
            let label = UILabel()
            label.text = "\(long.index)"
            label.font = UIFont.systemFont(ofSize: 11)
            titleContentView.addSubview(label)
            label.sizeToFit()
            label.center = CGPoint(x: long.posX, y: 10)
        }
    }
    
    
}

extension YXRulerView: UIScrollViewDelegate {
    
    public func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
        handleScrollEnd()
    }
    
    func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
        handleScrollEnd()
    }
    
    private func handleScrollEnd() {
        let offsetX = getValuePosX(by: contentView.contentOffset.x)
        let offsetY = contentView.contentOffset.y
        contentView.layoutIfNeeded()
        contentView.setContentOffset(.init(x: offsetX, y: offsetY), animated: false)
        
    }
    
    private func getValuePosX(by offsetX: CGFloat) ->CGFloat {
        let insetLet = contentView.contentInset.left
        let targetIndex = lround( (offsetX + insetLet) / (scaleLayer.space + scaleLayer.lineWidth)) // 四舍五
        if targetIndex < 0 || targetIndex >= scaleLayer.dataArr.count {
            return offsetX
        }
        print("=====targetIndex:\(targetIndex)")
        let entity = scaleLayer.dataArr[targetIndex]
        let targetX = entity.posX - insetLet - scaleLayer.lineWidth/4
        return targetX
    }
    
}

3、具体使用

       let ruler = YXRulerView()
        let arr = (1...9).map{ _ in Int.random }
        print("arr: \(arr)")
        ruler.setData(arr)
        view.addSubview(ruler)
        NSLayoutConstraint.activate([
            ruler.centerYAnchor.constraint(equalTo: view.centerYAnchor),
            ruler.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            ruler.widthAnchor.constraint(equalTo: view.widthAnchor),
            ruler.heightAnchor.constraint(equalToConstant: 100),
        ])

4、单独的刻度layer绘制

 let arr = (1...4).map{ _ in Int.random }
        let sLayer = YXScaleLayer()
        sLayer.lineWidth = 1.0
        sLayer.strokeColor = UIColor.lightGray.cgColor
        sLayer.frame = CGRect(x: 10, y: 100, width: 0, height: 100)
        sLayer.setData(arr)
        view.layer.addSublayer(sLayer)
        
        sLayer.backgroundColor = UIColor.cyan.cgColor

5、其他

extension Int {
    /// 4 ~ 9 随机数字
    static var random: Int {
        Int(arc4random()%6 + 4)
    }
}