模仿角度环形渐变 Circle progress

效果图如下:

demo.png
示例mask.png

思路如下:

1.创建两个线性渐变. 一个正 一个旋转180°

2.创建mask环形图层

总结:找到需要递进的颜色,环绕着,像接龙一样用线性渐变实现.

        strokColor = UIColor.gray
        //MARK: - set you need startAngle endAngle  设置你的开始点 结束点
        let path = UIBezierPath(arcCenter: CGPoint(x:bounds.width/2,y:bounds.height/2), radius: 90, startAngle: degreesToRadians(angle: -240), endAngle: degreesToRadians(angle: 60), clockwise: true)
      //track 层
        trackLayer = CAShapeLayer()
        trackLayer.frame = bounds
        self.layer.addSublayer(trackLayer)
        trackLayer.fillColor = UIColor.clear.cgColor
        trackLayer.strokeColor = strokColor.cgColor
        trackLayer.opacity = 0.2
        trackLayer.lineCap = kCALineCapSquare
        trackLayer.lineWidth = 15
        trackLayer.path = path.cgPath
     //mask 层
        progressLayer = CAShapeLayer()
        progressLayer.frame = bounds
        progressLayer.fillColor = UIColor.clear.cgColor
        progressLayer.strokeColor = UIColor.cyan.cgColor
        progressLayer.lineCap = kCALineCapSquare
        progressLayer.lineWidth = 15
        progressLayer.strokeEnd = 0.0
        progressLayer.path = path.cgPath
        
        let gradientLayer = CALayer()
        
      //MARK: - leftGradientLayer 左边渐变层
        let leftGradientLayer = CAGradientLayer()
        leftGradientLayer.frame = CGRect(x: 0, y: 0, width: bounds.width/2, height: bounds.height)
        leftGradientLayer.colors = [UIColor(red: 62/255.0, green: 154/255.0, blue: 205/255.0, alpha: 0.01).cgColor,UIColor(red: 62/255.0, green: 154/255.0, blue: 205/255.0, alpha: 0.5).cgColor]
        leftGradientLayer.locations = [0.4,1];
        leftGradientLayer.startPoint = CGPoint(x: 0.5, y: 1)
        leftGradientLayer.endPoint = CGPoint(x: 0.5, y: 0)
        gradientLayer.addSublayer(leftGradientLayer)
        
      //MARK: - rightGradientLayer 右边渐变层
        let rightGradientLayer = CAGradientLayer()
        rightGradientLayer.frame = CGRect(x: bounds.width/2, y: 0, width: bounds.width/2, height: bounds.height)
        rightGradientLayer.colors = [UIColor(red: 62/255.0, green: 154/255.0, blue: 205/255.0, alpha: 0.5).cgColor, UIColor(red: 62/255.0, green: 154/255.0, blue: 205/255.0, alpha: 1).cgColor]
        rightGradientLayer.locations = [0.2,1];
        rightGradientLayer.startPoint = CGPoint(x: 0.5, y: 0)
        rightGradientLayer.endPoint = CGPoint(x: 0.5, y: 1)
        gradientLayer.addSublayer(rightGradientLayer)
        
        gradientLayer.mask = progressLayer
        self.layer.addSublayer(gradientLayer)

参考链接
Code