Swift：二阶贝塞尔曲线的联动

目录

• 曲线上点算法
• 点的手势处理：点击线生成点和距离线有效距离内拖动生成点
• 方格和曲线交叉点的坐标获取

####一、曲线上点算法

• 1.1、思路：根据坐标上的点，计算控制点，从而再通过控制点之间分割成100个点(具体的控制点之间点的个数可以自己定义)，通过每个控制点之间的计算生成点，最后串起来就是上图看到的曲线

• 1.2、部分代码

  //MARK: 通过已知点绘制path
  private func calculate(pointList: [CGPoint]) {
      allPointList.removeAll()
      let path = CGMutablePath()
      // 曲线斜率
      let sharpenRatio = 1.0
      if (pointList.count < 3) {
          path.addLines(between: pointList)
          drawPath(path: path)
          return
      }
      var pMidOfLm = CGPoint()
      var pMidOfMr = CGPoint()
      var cache: CGPoint? = nil
      var startPoint = pointList[0]
      for i in 0...pointList.count - 3 {
          let pL = pointList[I]
          let pM = pointList[i + 1]
          let pR = pointList[i + 2]
          pMidOfLm.x = (pL.x + pM.x) / 2.0
          pMidOfLm.y = (pL.y + pM.y) / 2.0
          pMidOfMr.x = (pM.x + pR.x) / 2.0
          pMidOfMr.y = (pM.y + pR.y) / 2.0
          let lengthOfLm = distanceBetweenPoints(pL, pM)
          let lengthOfMr = distanceBetweenPoints(pR, pM)
          var ratio = lengthOfLm / (lengthOfLm + lengthOfMr) * sharpenRatio
          let oneMinusRatio = (1 - ratio) * sharpenRatio
          let dx = pMidOfLm.x - pMidOfMr.x
          let dy = pMidOfLm.y - pMidOfMr.y
          var cLeft = CGPoint()
          cLeft.x = pM.x + dx * ratio
          cLeft.y = pM.y + dy * ratio
          var cRight = CGPoint()
          cRight.x = pM.x + -dx * oneMinusRatio
          cRight.y = pM.y + -dy * oneMinusRatio
          if (i == 0) {
              let pMidOfLCLeft = CGPoint(x: (pL.x + cLeft.x) / 2.0, y: (pL.y + cLeft.y) / 2.0)
              let pMidOfCLeftM = CGPoint(x: (cLeft.x + pM.x) / 2.0, y: (cLeft.y + pM.y) / 2.0)
              let length1 = distanceBetweenPoints(cLeft, pL)
              let length2 = distanceBetweenPoints(cLeft, pM)
              ratio = length1 / (length1 + length2) * sharpenRatio
              var first = CGPoint()
              first.x = cLeft.x + (pMidOfLCLeft.x - pMidOfCLeftM.x) * ratio
              first.y = cLeft.y + (pMidOfLCLeft.y - pMidOfCLeftM.y) * ratio
              addPoint(startPoint, first, cLeft, pM)
              startPoint = pM
          } else {
              // bezierPath.move(to: startPoint)
              if let weakCache = cache {
                  // bezierPath.addCurve(to: pM, control1: weakCache, control2: cLeft)
                  addPoint(startPoint, weakCache, cLeft, pM)
                  startPoint = pM
              }
          }
          cache = cRight
          if (i == pointList.count - 3) {
              let pMidOfMCRight = CGPoint(x: (pM.x + cRight.x) / 2.0, y: (pM.y + cRight.y) / 2.0)
              let pMidOfCRightR = CGPoint(x: (pR.x + cRight.x) / 2.0, y: (pR.y + cRight.y) / 2.0)
              let length1 = distanceBetweenPoints(cRight, pM)
              let length2 = distanceBetweenPoints(pR, cRight)
              ratio = length2 / (length1 + length2) * sharpenRatio
              var last = CGPoint()
              last.x = cRight.x + (pMidOfCRightR.x - pMidOfMCRight.x) * ratio
              last.y = cRight.y + (pMidOfCRightR.y - pMidOfMCRight.y) * ratio
              // startPoint = pM
              // bezierPath.move(to: startPoint)
              // bezierPath.addCurve(to: pR, control1: cRight, control2: last)
              addPoint(startPoint, cRight, last, pR)
          }
      }
      path.addLines(between: allPointList)
      drawPath(path: path)
  }

####二、点的手势处理

• 2.1、点击线生成点

  分析 ：点击线的话，首先是拿到点击点的坐标p0，根据这个坐标，获取这个点与线垂直和水平交叉点的坐标p1和p2，看这个两个点到p0距离 代码示例：

  //MARK: 父视图点击手势
  ///  父视图点击手势
  /// - Parameter panGesture: 手势
  @objc func superTapGester(gesture: UITapGestureRecognizer) {
      guard let currentPath, isCanUserInteractionEnabled, points.count < maxCircleViewNumber else {
          return
      }
      let tapLocation = gesture.location(in: self)
      debugPrint("Tap location in parent view: \(tapLocation)")
      // 1、点击点首先要在 左右两个点的矩形内，如果不在不生点
      var previousPoint: CGPoint = CGPoint()
      var nextPoint: CGPoint = CGPoint()
      /// 要插入的index
      var insertIndex: Int = 0
      for (index, item) in points.enumerated() {
          if tapLocation.x < item.x {
              insertIndex = index
              // 找到后面的点
              nextPoint = item
              break
          }
          previousPoint = item
      }
      guard tapLocation.x > previousPoint.x && tapLocation.y < previousPoint.y && tapLocation.x < nextPoint.x && tapLocation.y > nextPoint.y else {
          debugPrint("❌不在矩形范围内", "previousPoint：\(previousPoint) nextPoint：\(nextPoint)")
          return
      }
      // 在矩形的范围内，确定添加的点事垂直点还是水平点
      // 垂直点
      let vPoint = getPointXY(xy: tapLocation.x, path: currentPath)
      // 水平点
      let hPoint = getPointXY(xy: tapLocation.y, path: currentPath, isX: false)
      // 垂直长度
      let vLength: CGFloat = abs(tapLocation.y - vPoint.y)
      // 水平长度
      let hLength: CGFloat = abs(tapLocation.x - hPoint.x)
      guard vLength < effectiveDistance || hLength < effectiveDistance else {
          debugPrint("✅在矩形范围内 ❌：不在有效距离：\(effectiveDistance) 内， 垂直距离：\(vLength) 水平距离：\(hLength)")
          return
      }
      // 在有效的范围内
      var point: CGPoint = CGPoint()
      if vLength < hLength {
          point = vPoint
          debugPrint("✅在矩形范围内：取值垂直的点")
      } else {
          point = hPoint
          debugPrint("✅在矩形范围内：取值水平的点")
      }
      // 2、在矩形内，生成一个点
      let view = CircleView()
      view.layer.cornerRadius = 7.5
      view.clipsToBounds = false
      view.backgroundColor = .randomColor
      view.layer.borderWidth = 3
      view.layer.borderColor = UIColor.white.cgColor
      view.tag = insertIndex + 100
      self.addSubview(view)
      // 插入视图
      circleViews.insert(view, at: insertIndex)
      // 插入生成的点
      points.insert(point, at: insertIndex)
    
      // 改变其他视图的tag
      for index in (insertIndex + 1)...(circleViews.count - 1) {
          circleViews[index].tag = index + 100
      }
    
      let panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(panGester))
      view.addGestureRecognizer(panGestureRecognizer)
    
      view.snp.makeConstraints { make in
          make.center.equalTo(point)
          make.size.equalTo(CGSize(width: 15, height: 15))
      }
    
      // 加震动
      let generator = UINotificationFeedbackGenerator()
      generator.notificationOccurred(.success)
    
      let param = getParamPointArray()
      dataClosure?(param.cmd_state, param.auxiliary_curve)
  }

• 2.2、距离线有效距离内拖动生成点 分析 ：拖动的话，首先是拿到点拖动起点的坐标p0，根据p0的坐标xy，分别获取曲线上的点p1和p2，同2.1一样拿到p0与两点的距离，看是否在有效距离effectiveDistance内，如果在看谁距离很近，近的则是点生成点的起点，从而拖动中点跟着移动，这个是利用的父视图的拖动手势 代码示例：

  //MARK: 父视图拖动手势
  ///  父视图拖动手势
  /// - Parameter panGesture: 手势
  @objc func superPanGester(panGesture: UIPanGestureRecognizer) {
      // 最多maxCircleViewNumber个点，包含两头的点
      guard isCanUserInteractionEnabled, points.count < maxCircleViewNumber else {
          return
      }
      switch panGesture.state {
      case .began:
          let startPanLocation = panGesture.location(in: self)
          let result = isPointLine(point: startPanLocation)
          if result.isEffectivePoint {
              // 在拖动开始的位置生成一个点
              superPanInserTag = 100 + result.insertIndex
              // 2、在矩形内，生成一个点
              let view = CircleView()
              view.layer.cornerRadius = 7.5
              view.clipsToBounds = false
              view.backgroundColor = .randomColor
              view.layer.borderWidth = 3
              view.layer.borderColor = UIColor.white.cgColor
              view.tag = superPanInserTag
              self.addSubview(view)
              // 插入视图
              circleViews.insert(view, at: result.insertIndex)
              // 插入生成的点
              points.insert(startPanLocation, at: result.insertIndex)
            
              // 改变其他视图的tag
              for index in (result.insertIndex + 1)...(circleViews.count - 1) {
                  circleViews[index].tag = index + 100
              }
            
              let panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(panGester))
              view.addGestureRecognizer(panGestureRecognizer)
            
              view.snp.makeConstraints { make in
                  make.center.equalTo(startPanLocation)
                  make.size.equalTo(CGSize(width: 15, height: 15))
              }
              setNeedsDisplay()
              // 加震动
              let generator = UINotificationFeedbackGenerator()
              generator.notificationOccurred(.success)
          }
          debugPrint("super-拖动开始: \(startPanLocation) superPanInserTag:\(superPanInserTag)")
      case .changed:
          let tapLocation = panGesture.location(in: self)
          if superPanInserTag > 0 {
              debugPrint("super-拖动中: \(tapLocation) inserTag:\(superPanInserTag)")
              // 添加的点跟着移动
              let panGestureRecognizerTag = superPanInserTag - 100
              let previousPoint: CGPoint = points[panGestureRecognizerTag - 1]
              let nextPoint: CGPoint = points[panGestureRecognizerTag + 1]
              guard tapLocation.x > previousPoint.x && tapLocation.y < previousPoint.y && tapLocation.x < nextPoint.x && tapLocation.y > nextPoint.y else {
                  debugPrint("❌不在矩形范围内", "previousPoint：\(previousPoint) nextPoint：\(nextPoint)")
                  // 移除该点
                  points.remove(at: panGestureRecognizerTag)
                  let view = circleViews[panGestureRecognizerTag]
                  circleViews.remove(at: panGestureRecognizerTag)
                  view.removeFromSuperview()
                  for index in panGestureRecognizerTag...(circleViews.count - 1) {
                      circleViews[index].tag = index + 100
                  }
                  // 加震动
                  let generator = UINotificationFeedbackGenerator()
                  generator.notificationOccurred(.success)
                  superPanInserTag = 0
                  setNeedsDisplay()
                  return
              }
              let view = circleViews[panGestureRecognizerTag]
              view.snp.updateConstraints { make in
                  make.center.equalTo(tapLocation)
              }
              points[panGestureRecognizerTag] = tapLocation
              debugPrint("打印tag：\(panGestureRecognizerTag)")
              setNeedsDisplay()
          }
      case .ended:
          superPanInserTag = 0
          debugPrint("super-拖动结束 新的value")
      default:
          debugPrint("super-其他")
      }
  }
  
  //MARK: 是否响应父视图拖动的手势
  /// 是否响应拖动的手势：实现 gestureRecognizer(_:shouldReceive:) 方法
  func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldReceive touch: UITouch) -> Bool {
      // 根据条件决定是否响应手势
      if isCanUserInteractionEnabled {
          let location = touch.location(in: self)
          let result = isPointLine(point: location)
          return result.isEffectivePoint
       } else {
          return false
       }
  }

####三、方格和曲线交叉点的坐标获取

• 3.1、方格 这个花方格就比较简单了，只需要两个for循环即可

  class GridView: UIView {
      override init(frame: CGRect) {
          super.init(frame: frame)
      }
  
      override func draw(_ rect: CGRect) {
          super.draw(rect)
          let width: CGFloat = rect.size.width
          let height: CGFloat = rect.size.height
          // 创建一个UIBezierPath对象
          let path = UIBezierPath()
    
          // 设置线宽和颜色
          UIColor.yellow.setStroke()
          path.lineWidth = 1.0
          let lineVWidth: CGFloat = height / 10.0
          // 绘制水平线
          for i in 0...10 {
              path.move(to: CGPoint(x: 0, y: CGFloat(i) * lineVWidth))
              path.addLine(to: CGPoint(x: width, y: CGFloat(i) * lineVWidth))
          }
    
          // 绘制垂直线
          let lineHWidth: CGFloat = width / 10.0
          for i in 0...10 {
              path.move(to: CGPoint(x: CGFloat(i) * lineHWidth, y: 0))
              path.addLine(to: CGPoint(x: CGFloat(i) * lineHWidth, y: height))
          }
          // 将路径添加到视图中并绘制
          path.stroke()
      }
  
      required init?(coder: NSCoder) {
          fatalError("init(coder:) has not been implemented")
      }
  }

• 3.2、方格和曲线交叉点的坐标获取

  //MARK: - CGMutablePath曲线-根据x坐标获取y坐标
  extension BezierCurveView {
      //MARK: 根据某个点的x坐标获取y坐标
      /// 根据某个点的x坐标获取y坐标
      /// - Parameters:
      ///   - x: x / y坐标
      ///   - path: CGMutablePath
      /// - Returns: description
      private func getPointXY(xy: CGFloat, path: CGPath, isX: Bool = true) -> CGPoint {
          var value: CGFloat = 0.0
          var prevPoint = CGPoint.zero
          path.applyWithBlock { element in
              switch element.pointee.type {
              case .moveToPoint:
                  prevPoint = element.pointee.points[0]
              case .addLineToPoint:
                  let startPoint = prevPoint
                  let endPoint = element.pointee.points[0]
                  if isX {
                      if xy >= startPoint.x && xy <= endPoint.x {
                          let t = (xy - startPoint.x) / (endPoint.x - startPoint.x)
                          value = startPoint.y + t * (endPoint.y - startPoint.y)
                      }
                  } else {
                      if xy <= startPoint.y && xy >= endPoint.y {
                          let t = (xy - startPoint.y) / (endPoint.y - startPoint.y)
                          value = startPoint.x + t * (endPoint.x - startPoint.x)
                      }
                  }
                  prevPoint = endPoint
              default:
                  break
              }
          }
          return isX ? CGPoint(x: xy, y: value) : CGPoint(x: value, y: xy)
      }
  }

demo地址 更多的扩展请参考另一个基础库JKSwiftExtension