如何使用CAShapeLayer绘制一个圆圈，以编程方式在swift中以自定义UIView为中心

Question

我试图在自定义UIView中使用CAShapeLayer绘制一个圆形进度条，这是自动约束，我不想在我的超级视图的中心绘制我的圆，而是在我的自定义视图的中心，因为我有其他顶部的视图我的代码下面绘制一个圆圈，但它没有位于指定的视图中

// 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)

Answer 1

如果在设计时未自行设置框架，则可以考虑在将所有约束应用于视图后添加图层。这就像我在一个例子中测试过的那样。

 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)
        }

Answer 2

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

下面是一个代码，它将一个形状图层添加到我在示例应用程序故事板中添加并作为IBOutlet连接的视图中：

@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)
}

我更改了颜色和alpha周围，并在形状图层中添加了borderWidth以使一切都突出。

Answer 3

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)
}