顯示CAShapeLayers

Question

我已經創建CAShapeLayers的陣列，以便繪製在不同層上不同顏色的圓弧的不同部分的陣列，這是我的代碼：

import UIKit 

class ViewController: UIViewController { 

    var level = 0.0 
    var old_level = 0.75 

    var progressLayer: [CAShapeLayer] = [] 
    var circle = UIView() 

    override func viewDidLoad() { 

     circle = UIView(frame: CGRect(x: 0, y: 0, width: view.frame.size.width, height: view.frame.size.height)) 

     view.addSubview(circle) 

     update_curve(value: 10) 
     update_curve(value: 20) 
     update_curve(value: 10) 

    } 

    func update_curve(value: Double){ 

     level = value*(1.5/100)+0.75 

     progressLayer.append(CAShapeLayer()) 

     var progressPath = UIBezierPath(arcCenter: CGPoint(x: progressLayer[layerindex].frame.size.width/2, y: progressLayer[layerindex].frame.size.height/2), radius: CGFloat(100), startAngle: CGFloat(M_PI*old_level), endAngle:CGFloat(level*M_PI), clockwise: true) 

     circle.layer.addSublayer(progressLayer[layerindex]) 
     progressLayer[layerindex].frame = view.bounds 

     progressLayer[layerindex].path = progressPath.cgPath 

     progressLayer[layerindex].fillColor = UIColor.clear.cgColor 

     progressLayer[layerindex].strokeColor = generateRandomColor() 

     progressLayer[layerindex].lineWidth = 20.0 

     let animation2 = CABasicAnimation(keyPath: "strokeEnd") 

     animation2.fromValue = 0.0 
     animation2.toValue = 1.0 
     animation2.duration = 1 
     animation2.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut) 

     progressLayer[layerindex].add(animation2, forKey: "drawLineAnimation") 

     layerindex += 1 
     old_level = level 
    } 

    func generateRandomColor() -> UIColor { 
     let hue : CGFloat = CGFloat(arc4random() % 256)/256 // use 256 to get full range from 0.0 to 1.0 
     let saturation : CGFloat = CGFloat(arc4random() % 128)/256 + 0.5 // from 0.5 to 1.0 to stay away from white 
     let brightness : CGFloat = CGFloat(arc4random() % 128)/256 + 0.5 // from 0.5 to 1.0 to stay away from black 

     return UIColor(hue: hue, saturation: saturation, brightness: brightness, alpha: 1) 
    } 
} 

但是，當運行此代碼， iPhone的屏幕上沒有任何東西出現，但我沒有收到錯誤。我究竟做錯了什麼？

Answer 1

我剛剛意識到progressLayer的框架是在定義progressPath之後定義的。 update_curve函數的代碼應爲：

func update_curve(value: Double){ 

    level = value*(1.5/100)+0.75 

    progressLayer.append(CAShapeLayer()) 

    progressLayer[layerindex].frame = view.bounds 

    var progressPath = UIBezierPath(arcCenter: CGPoint(x: progressLayer[layerindex].frame.size.width/2, y: progressLayer[layerindex].frame.size.height/2), radius: CGFloat(100), startAngle: CGFloat(M_PI*old_level), endAngle:CGFloat(level*M_PI), clockwise: true) 

    circle.layer.addSublayer(progressLayer[layerindex]) 

    progressLayer[layerindex].path = progressPath.cgPath 

    progressLayer[layerindex].fillColor = UIColor.clear.cgColor 

    progressLayer[layerindex].strokeColor = generateRandomColor() 

    progressLayer[layerindex].lineWidth = 20.0 

    let animation2 = CABasicAnimation(keyPath: "strokeEnd") 

    animation2.fromValue = 0.0 
    animation2.toValue = 1.0 
    animation2.duration = 1 
    animation2.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut) 

    progressLayer[layerindex].add(animation2, forKey: "drawLineAnimation") 

    layerindex += 1 
    old_level = level 
}