如何更改CAShapeLayer alpha/opacity值？

Question

我似乎不能改变我的CAShapeLayer的不透明度，无论我做什么。我尝试设置不透明度：

    bottomProgressBar.strokeColor = UIColor.white.cgColor
    bottomProgressBar.opacity = 0.1

没有起作用。然后我试了一下：

bottomProgressBar.strokeColor = UIColor(displayP3Red: 255, green: 255, blue: 255, alpha: 0.1).cgColor

在这两种情况下，alpha值都是1。

有没有其他方法可以做到这一点？还是我把它们设置错了？

编辑：

下面是我的代码：

这是一个继承自UIView的类

override init(frame: CGRect) {
    super.init(frame: frame)
    configure()
}

required init?(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
    configure()
}

func configure() {
    bottomProgressBar.strokeColor = UIColor.white.cgColor
    bottomProgressBar.opacity = 0.1
    bottomProgressBar.lineWidth = self.frame.height
    bottomProgressBar.strokeStart = 0
    bottomProgressBar.strokeEnd = 1
    self.layer.addSublayer(bottomProgressBar)

    topProgressBar.strokeColor = UIColor.white.cgColor
    topProgressBar.lineWidth = self.frame.height
    topProgressBar.strokeStart = 0
    topProgressBar.strokeEnd = 1
    self.layer.addSublayer(topProgressBar)
}

编辑2：

override func layoutSubviews() {
    super.layoutSubviews()

    let path = UIBezierPath()
    path.move(to: CGPoint(x: 0, y: 0))
    path.addLine(to: CGPoint(x: self.frame.width, y: 0))

    bottomProgressBar.path = path.cgPath
    topProgressBar.path = path.cgPath
}

编辑3：

​

​

Answer 1

我认为发生的情况是，您没有为要渲染的形状定义路径。

    func configure() {
        let path = UIBezierPath(rect: CGRect(x: 0, y: 0, width: self.frame.width, height: self.frame.height))
        bottomProgressBar.frame = self.frame
        bottomProgressBar.bounds = self.bounds
        bottomProgressBar.path = path.cgPath
        bottomProgressBar.strokeColor = UIColor.red.cgColor
        bottomProgressBar.opacity = 0.1
//      no need for the following line as dimensions are already defined
//      bottomProgressBar.lineWidth = self.frame.height
//      bottomProgressBar.strokeStart = 0
//      bottomProgressBar.strokeEnd = 200
        self.layer.addSublayer(bottomProgressBar)

        // path width divided by 2 for demo
        let topPath = UIBezierPath(rect: CGRect(x: 0, y: 0, width: self.frame.width/2, height: self.frame.height))
        topProgressBar.frame = self.frame
        topProgressBar.bounds = self.bounds
        topProgressBar.path = topPath.cgPath
        topProgressBar.strokeColor = UIColor.green.cgColor
        self.layer.addSublayer(topProgressBar)
    }

希望这能有所帮助。

Answer 2

奇怪的是它不能为你工作，因为是.opacity改变了我的layer's alpha：

let circularPath = UIBezierPath(arcCenter: view.center,
                                          radius: (100,
                                          startAngle: -.pi/2,
                                          endAngle: 3 * .pi/2,
                                          clockwise: true)
let shapeLayer = CAShapeLayer()
shapeLayer.path = circularPath.cgPath
shapeLayer.strokeColor = UIColor.red.cgColor
shapeLayer.fillColor = UIColor.clear.cgColor
shapeLayer.lineWidth = 6

shapeLayer.opacity = 0.3 // *** fades out the shape layer ***