关于 ios：如何使用 CAShapeLayer 以编程方式以自定义 UIView 为中心绘制一个圆


How to draw a circle using CAShapeLayer to be centered in a custom UIView in swift programmatically

我正在尝试使用 CAShapeLayer 在已自动约束的自定义 UIView 中绘制圆形进度条，我不想在我的超级视图的中心绘制我的圆圈，而是在我的自定义视图的中心因为我在上面有其他视图，所以下面的代码绘制了一个圆圈，但它没有定位在指定的视图中

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// Custom View
let gaugeViewHolder = UIView()
scrollView.addSubview(gaugeViewHolder)
        gaugeViewHolder.translatesAutoresizingMaskIntoConstraints = false
        gaugeViewHolder.backgroundColor = UIColor.black
        gaugeViewHolder.leadingAnchor.constraint(equalTo: motherView.leadingAnchor).isActive = true
        gaugeViewHolder.topAnchor.constraint(equalTo: defaultAccImage.bottomAnchor, constant: 70).isActive = true
        gaugeViewHolder.trailingAnchor.constraint(equalTo: motherView.trailingAnchor).isActive = true
        gaugeViewHolder.heightAnchor.constraint(equalToConstant: 200).isActive = true

//Now my circle
let shapeLayer = CAShapeLayer()
        let centerForGauge = gaugeViewHolder.center

        let circularPath = UIBezierPath(arcCenter: centerForGauge
            , radius: 80, startAngle: 0, endAngle: 2 * CGFloat.pi, clockwise: true)

        shapeLayer.path = circularPath.cgPath
        shapeLayer.strokeColor = UIColor.white.withAlphaComponent(0.20).cgColor
        shapeLayer.lineWidth = 10
        shapeLayer.fillColor = UIColor.clear.cgColor
        shapeLayer.lineCap = kCALineCapRound
        gaugeViewHolder.layer.addSublayer(shapeLayer)
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let gaugeViewHolder = UIView()
 override func viewDidLoad() {
    super.viewDidLoad()
scrollView.addSubview(gaugeViewHolder)
    gaugeViewHolder.translatesAutoresizingMaskIntoConstraints = false
    gaugeViewHolder.backgroundColor = UIColor.black
    gaugeViewHolder.leadingAnchor.constraint(equalTo: motherView.leadingAnchor).isActive = true
    gaugeViewHolder.topAnchor.constraint(equalTo: defaultAccImage.bottomAnchor, constant: 70).isActive = true
    gaugeViewHolder.trailingAnchor.constraint(equalTo: motherView.trailingAnchor).isActive = true
    gaugeViewHolder.heightAnchor.constraint(equalToConstant: 200).isActive = true
}

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    let shapeLayer = CAShapeLayer()
    let centerForGauge = gaugeViewHolder.center
    print("gauge width:: \\(centerForGauge)")
    let circularPath = UIBezierPath(arcCenter: CGPoint(x: gaugeViewHolder.frame.size.width/2, y: gaugeViewHolder.frame.size.height/2)
        , radius: 100, startAngle: 0, endAngle: 2 * CGFloat.pi, clockwise: true)

    shapeLayer.path = circularPath.cgPath
    shapeLayer.strokeColor = UIColor.white.withAlphaComponent(0.50).cgColor
    shapeLayer.lineWidth = 10
    shapeLayer.fillColor = UIColor.clear.cgColor
    shapeLayer.lineCap = kCALineCapRound
    gaugeViewHolder.layer.addSublayer(shapeLayer)
}

你永远不会设置形状图层的框架。如果您希望形状层覆盖视图的矩形，它应该是拥有视图的边界矩形。

以下代码将形状层添加到我在示例应用故事板中添加并连接为 IBOutlet 的视图中：

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@IBOutlet weak var gaugeViewHolder: UIView!

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    gaugeViewHolder.backgroundColor = UIColor.lightGray

    //Now my circle
    let shapeLayer = CAShapeLayer()
    shapeLayer.borderWidth = 2.0 //Add a box on the shape layer so you can see where it gets drawn.

    shapeLayer.frame = gaugeViewHolder.bounds  //Use the view's bounds as the layer's frame

    //Convert gaugeViewHolder's center from it's superview's coordinate system to it's coordinate system
    let centerForGauge = gaugeViewHolder?.superview?.convert(gaugeViewHolder.center, to: gaugeViewHolder) ?? CGPoint.zero

    let lineWidth = CGFloat(5.0)

    //Use 1/2 the shortest side of the shapeLayer's frame for the radius, inset for the circle path's thickness.
    let radius = max(shapeLayer.frame.size.width, shapeLayer.frame.size.height)/2.0 - lineWidth / 2.0

    let circularPath = UIBezierPath(arcCenter: centerForGauge
        , radius: radius, startAngle: 0, endAngle: 2 * CGFloat.pi, clockwise: true)

    shapeLayer.path = circularPath.cgPath
    shapeLayer.strokeColor = UIColor.black.cgColor
    shapeLayer.lineWidth = lineWidth
    shapeLayer.fillColor = UIColor.yellow.cgColor
    shapeLayer.lineCap = .round
    gaugeViewHolder.layer.addSublayer(shapeLayer)
}

我更改了周围的颜色和 alpha，并在形状图层中添加了一个边框宽度，以使所有内容都脱颖而出。

如果您没有在设计时自行设置框架，您可以考虑在所有约束都应用到您的视图之后再添加该层。正如我在一个示例中测试过的那样。

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 var gaugeViewHolder : UIView!

     override func viewDidLoad() {
        super.viewDidLoad()
        gaugeViewHolder = UIView()
        scrollView.addSubview(gaugeViewHolder)
        gaugeViewHolder.translatesAutoresizingMaskIntoConstraints = false
        gaugeViewHolder.backgroundColor = UIColor.black
        gaugeViewHolder.leadingAnchor.constraint(equalTo: motherView.leadingAnchor).isActive = true
        gaugeViewHolder.topAnchor.constraint(equalTo: defaultAccImage.bottomAnchor, constant: 70).isActive = true
        gaugeViewHolder.trailingAnchor.constraint(equalTo: motherView.trailingAnchor).isActive = true
        gaugeViewHolder.heightAnchor.constraint(equalToConstant: 200).isActive = true
}


  override func viewDidAppear(_ animated: Bool) {
                super.viewDidAppear(animated)
            let shapeLayer = CAShapeLayer()
            let centerForGauge = gaugeViewHolder.center
            let circularPath = UIBezierPath(arcCenter: centerForGauge
                , radius: 80, startAngle: 0, endAngle: 2 * CGFloat.pi, clockwise: true)

            shapeLayer.path = circularPath.cgPath
            shapeLayer.strokeColor = UIColor.white.withAlphaComponent(0.20).cgColor
            shapeLayer.lineWidth = 10
            shapeLayer.fillColor = UIColor.clear.cgColor
            shapeLayer.lineCap = CAShapeLayerLineCap.round
            gaugeViewHolder.layer.addSublayer(shapeLayer)
        }
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