iOS新增绘制圆的方法实例代码

addArc(withCenter:, radius:, startAngle:, endAngle:, clockwise:)

addCurve(to:, controlPoint1:, controlPoint2:)

addArc(startPoint: , endPoint: , angle: , clockwise:)

func calculateLineLength(_ point1: CGPoint, _ point2: CGPoint) -> CGFloat {
  let w = point1.x - point2.x
  let h = point1.y - point2.y
  return sqrt(w * w + h * h)
}

func calculateAngle(point: CGPoint, origin: CGPoint) -> Double {
  
  if point.y == origin.y {
    return point.x > origin.x ? 0.0 : -Double.pi
  }
  
  if point.x == origin.x {
    return point.y > origin.y ? Double.pi * 0.5 : Double.pi * -0.5
  }
  // Note: 修正标准坐标系角度到 iOS 坐标系
  let rotationAdjustment = Double.pi * 0.5
  
  let offsetX = point.x - origin.x
  let offsetY = point.y - origin.y
  // Note: 使用 -offsetY 是因为 iOS 坐标系与标准坐标系的区别
  if offsetY > 0 {
    return Double(atan(offsetX / -offsetY)) + rotationAdjustment
  } else {
    return Double(atan(offsetX / -offsetY)) - rotationAdjustment
  }
}

// Woring: 只计算从start到end **顺时针** 计算对应的 **小于π** 圆弧对应的圆心
// Note: 计算逆时针(end到start)可以看做将传入的start和end对调后计算顺时针时的圆心位置
// Note: 计算大于π的叫相当于将end和start对换后计算2π-angle的顺时针圆心位置
// Note: 综上传入start，end，angle 右外部自行处理逻辑
func calculateCenterFor(startPoint start: CGPoint, endPoint end: CGPoint, radian: Double) -> CGPoint {
  guard radian <= Double.pi else {
    fatalError("Does not support radian calculations greater than π!")
  }
  
  guard start != end else {
    fatalError("Start position and end position cannot be equal!")
  }
  
  if radian == Double.pi {
    let centerX = (end.x - start.x) * 0.5 + start.x
    let centerY = (end.y - start.y) * 0.5 + start.y
    return CGPoint(x: centerX, y: centerY)
  }
  
  let lineAB = calculateLineLength(start, end)
  
  // 平行 Y 轴
  if start.x == end.x {
    let centerY = (end.y - start.y) * 0.5 + start.y
    let tanResult = CGFloat(tan(radian * 0.5))
    let offsetX = lineAB * 0.5 / tanResult
    let centerX = start.x + offsetX * (start.y > end.y ? 1.0 : -1.0)
    return CGPoint(x: centerX, y: centerY)
  }
  
  // 平行 X 轴
  if start.y == end.y {
    let centerX = (end.x - start.x) * 0.5 + start.x
    let tanResult = CGFloat(tan(radian * 0.5))
    let offsetY = lineAB * 0.5 / tanResult
    let centerY = start.y + offsetY * (start.x < end.x ? 1.0 : -1.0)
    return CGPoint(x: centerX, y: centerY)
  }
  
  // 普通情况
  
  // 计算半径
  let radius = lineAB * 0.5 / CGFloat(sin(radian * 0.5))
  // 计算与 Y 轴的夹角
  let angleToYAxis = atan(abs(start.x - end.x) / abs(start.y - end.y))
  let cacluteAngle = CGFloat(Double.pi - radian) * 0.5 - angleToYAxis
  // 偏移量
  let offsetX = radius * sin(cacluteAngle)
  let offsetY = radius * cos(cacluteAngle)
  
  var centetX = end.x
  var centerY = end.y
  // 以 start 为原点判断象限区间(iOS坐标系)
  if end.x > start.x && end.y < start.y {
    // 第一象限
    centetX = end.x + offsetX
    centerY = end.y + offsetY
  } else if end.x > start.x && end.y > start.y {
    // 第二象限
    centetX = start.x - offsetX
    centerY = start.y + offsetY
  } else if end.x < start.x && end.y > start.y {
    // 第三象限
    centetX = end.x - offsetX
    centerY = end.y - offsetY
  } else if end.x < start.x && end.y < start.y {
    // 第四象限
    centetX = start.x + offsetX
    centerY = start.y - offsetY
  }
  
  return CGPoint(x: centetX, y: centerY)
}

func addArc(startPoint start: CGPoint, endPoint end: CGPoint, angle: Double, clockwise: Bool) {
  
  guard start != end && (angle >= 0 && angle <= 2 * Double.pi) else {
    return
  }
  if angle == 0 {
    move(to: start)
    addLine(to: end)
    return
  }
  
  var tmpStart = start, tmpEnd = end, tmpAngle = angle
  // Note: 保证计算圆心时是从 start 到 end 顺时针 小于 π 的角
  if tmpAngle > Double.pi {
    tmpAngle = 2 * Double.pi - tmpAngle
    (tmpStart, tmpEnd) = (tmpEnd, tmpStart)
  }
  if !clockwise {
    (tmpStart, tmpEnd) = (tmpEnd, tmpStart)
  }
  
  let center = calculateCenterFor(startPoint: tmpStart, endPoint: tmpEnd, radian: tmpAngle)
  let radius = calculateLineLength(start, center)
  
  var startAngle = calculateAngle(point: start, origin: center)
  var endAngle = calculateAngle(point: end, origin: center)
  // Note: 逆时针绘制则交换 startAngle 和 endAngle，并且将开始点移动的 end 位置
  if !clockwise {
    (startAngle, endAngle) = (endAngle, startAngle)
    move(to: end)
  }
  
  addArc(withCenter: center, radius: radius, startAngle: CGFloat(startAngle), endAngle: CGFloat(endAngle), clockwise: true)
  move(to: end)
}

override func draw(_ rect: CGRect) {
  
  let path = UIBezierPath()
  var start = CGPoint(x: 160, y: 130)
  var end = CGPoint(x: 180, y: 200)
  path.move(to: start)
  path.addArc(startPoint: start, endPoint: end, angle: Double.pi * 1.6, clockwise: true)
  path.move(to: start)
  path.addArc(startPoint: start, endPoint: end, angle: Double.pi * 0.8, clockwise: true)
  
  start = CGPoint(x: 142, y: 130)
  end = CGPoint(x: 162, y: 200)
  path.move(to: start)
  path.addArc(startPoint: start, endPoint: end, angle: Double.pi * 0.4, clockwise: true)
  
  start = CGPoint(x: 140, y: 130)
  end = CGPoint(x: 160, y: 200)
  path.move(to: start)
  path.addArc(startPoint: start, endPoint: end, angle: Double.pi * 1.6, clockwise: false)
  path.move(to: start)
  path.addArc(startPoint: start, endPoint: end, angle: Double.pi * 0.8, clockwise: false)
  
  path.close()
  path.lineWidth = 1
  UIColor.red.setStroke()
  path.stroke()
}

struct Angle {
  private var degress: Double
  static func deggess(_ degress: Double) -> Angle {
    return .init(degress: degress)
  }
  // 弧度
  var radians: Double { Double.pi * degress / 180.0 }
}

// Angle.deggess(90).radians // 1.570796326794897

func addArc(startPoint start: CGPoint, endPoint end: CGPoint, angle: Angle, clockwise: Bool)