private var path = UIBezierPath()
    private var shapeLayer = CAShapeLayer()

    override public func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        if let touch = touches.first as UITouch? {
            let touchPoint = touch.location(in: self)
            path.move(to: touchPoint)
        }
    }

    override public func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        if let touch = touches.first as UITouch? {
            let touchPoint = touch.location(in: self)
            path.addLine(to: touchPoint)
            shapeLayer.path = path.cgPath
            shapeLayer.strokeColor = strokeColor.cgColor
            shapeLayer.fillColor = UIColor.clear.cgColor
            shapeLayer.lineWidth = lineWidth
            layer.addSublayer(shapeLayer)
        }
    }

    override public func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        if let touch = touches.first as UITouch? {
            let touchPoint = touch.location(in: self)
            path.addLine(to: touchPoint)
            path.close()
            shapeLayer.path = path.cgPath
            shapeLayer.strokeColor = UIColor.clear.cgColor
            shapeLayer.fillColor = strokeColor.cgColor
            shapeLayer.lineWidth = lineWidth
            layer.addSublayer(shapeLayer)
        }
    }