ios - 用核心图形画线

Question

我想在核心图形中绘制不止一条直线。或保存该行并开始一个新行。我使用了两个触摸位置变量，并在 touch Began,Moved,Ended 中为它们分配了触摸位置，然后我使用了这个:

override func draw(_ rect: CGRect) {
    let context = UIGraphicsGetCurrentContext()
    context?.setStrokeColor(UIColor(red: 0, green: 0, blue: 0, alpha: 1.0).cgColor)
    context?.setLineWidth(5.0)
    context?.move(to: CGPoint(x: firstTouchLocation.x, y: firstTouchLocation.y))
    context?.addLine(to: CGPoint(x: lastTouchLocation.x, y: lastTouchLocation.y))
    context?.strokePath()
}

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    if let touch = touches.first {
        firstTouchLocation = touch.location(in: self)
        lastTouchLocation = firstTouchLocation
        setNeedsDisplay()
    }
}

override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
    if let touch = touches.first {
        lastTouchLocation = touch.location(in: self)
        setNeedsDisplay()
    }
}

override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
    if let touch = touches.first {
        lastTouchLocation = touch.location(in: self)
        setNeedsDisplay()
    }
}

Answer 1

尝试像这样使用 CAShapeLayer 画线:

func addLine(fromPoint start: CGPoint, toPoint end:CGPoint) {
       let line = CAShapeLayer()
       let linePath = UIBezierPath()
       linePath.move(to: start)
       linePath.addLine(to: end)
       line.path = linePath.cgPath
       line.strokeColor = UIColor.red.cgColor
       line.lineWidth = 1
       line.lineJoin = kCALineJoinRound
       self.view.layer.addSublayer(line)
   }

希望这对您有所帮助!