How to use CABasicAnimation and CALayer to animate a bezier path - ios

Question

I'm trying to animate color change of a bezier path in a UIView but I think I'm missing something very basic as the layer is not being rendered in my UI View. Just adding the layer to self.layer doesn't seem to trigger the draw in context method. I don't really understand the basics of which draw is being triggered when and into which layers.
public class ProgressIndicatorView: UIView {
var bubble = BubbleLayer()
public required init(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
public class var sharedInstance: ProgressIndicatorView {
struct Singleton {
static let instance = ProgressIndicatorView(frame: CGRect.zeroRect)
}
return Singleton.instance
}
public override init(frame: CGRect) {
super.init(frame: frame)
self.updateFrame(frame)
self.backgroundColor = UIColor(white: 0.0, alpha: 0.3)
self.layer.addSublayer(bubble)
}
func updateFrame(frame:CGRect)
{
self.frame = frame
bubble.frame = CGRect(x:self.center.x, y:self.center.y, width: 126, height: 126)
}
func animate(){
let anim = CABasicAnimation(keyPath:"percentage")
anim.fromValue = 0.000
anim.toValue = 1.000
anim.repeatCount = 1000
bubble.addAnimation(anim, forKey: "percentage")
}
public class func show() {
let window = UIApplication.sharedApplication().windows.first as UIWindow
let indicator = ProgressIndicatorView.sharedInstance
indicator.updateFrame(window.frame)
if indicator.superview == nil {
window.addSubview(indicator)
indicator.animate()
}
}
public class func hide(){
let indicator = ProgressIndicatorView.sharedInstance
UIView.animateWithDuration(0.33, delay: 0.0, options: .CurveEaseOut, animations: {
indicator.alpha = 0.0
}, completion: {_ in
indicator.alpha = 1.0
indicator.removeFromSuperview()
})
}
}
public class BubbleLayer : CALayer {
public var percentage:CGFloat = 0
public override func animationForKey(key: String!) -> CAAnimation! {
var anim = CABasicAnimation(keyPath: key)
anim.fromValue = self.presentationLayer().key
anim.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
anim.duration = CATransaction.animationDuration()
return anim
}
public override func actionForKey(event: String!) -> CAAction! {
if (event == "percentage"){
return self.animationForKey(event)
}
else {
return super.actionForKey(event)
}
}
public override func drawInContext(ctx: CGContext!) {
super.drawInContext(ctx)
UIGraphicsPushContext(ctx)
let context = UIGraphicsGetCurrentContext()
let frame = self.bounds
let white = UIColor(red: self.percentage, green: 1.000, blue: 1.000, alpha: 1.000)
let white_20 = UIColor(red: self.percentage, green: 1.000, blue: 1.000, alpha: 0.200)
//// Oval 10 Drawing
CGContextSaveGState(context)
CGContextTranslateCTM(context, 1.3, 0.8)
var oval10Path = UIBezierPath(ovalInRect: CGRectMake(5, 5, 113.6, 113.6))
white_20.setStroke()
oval10Path.lineWidth = 10
oval10Path.stroke()
CGContextRestoreGState(context)
//// Bezier 122 Drawing
var bezier122Path = UIBezierPath()
bezier122Path.moveToPoint(CGPointMake(63, 5.9))
bezier122Path.addCurveToPoint(CGPointMake(119.8, 62.7), controlPoint1: CGPointMake(94.4, 5.9), controlPoint2: CGPointMake(119.8, 31.3))
bezier122Path.lineCapStyle = kCGLineCapRound;
bezier122Path.lineJoinStyle = kCGLineJoinRound;
white.setStroke()
bezier122Path.lineWidth = 10
bezier122Path.stroke()
}
}