How to achieve this animation with multiple CAShapeLayer - swift

Question

I'm having a lot of trouble exporting a video with animated layers.
The final goal is to export to a video (that's why I need this done with CALayers) a moving CAShapeLayer around the screen and a line following its trace.
First of all, I have an array of CGPoint with all the coordinate points which a CAShapeLayer should use to animate itself. To create the animation I'm using a CAKeyframeAnimation.
let values = [CGPoint(x: 50, y: 100),
CGPoint(x: 100, y: 150)] //Example values
let animation = CAKeyframeAnimation()
animation.keyPath = "position"
animation.values = values
animation.duration = videoLength
With this, I'm able to show the CALayer moving around the screen. It's 1 value per frame of the video, it's a 1:1 value.
The real problem comes with adding a line that shows the path of the CAShapeLayer.
What I think I might do, is to create lines with UIBezierPath, animate them and add each line
lines.forEach { (line) in
let path = UIBezierPath()
let shapeLayer = CAShapeLayer()
for (index, point) in line.points.enumerated() {
if index == 0 {
path.move(to: point)
} else {
path.addLine(to: point)
}
}
shapeLayer.fillColor = UIColor.clear.cgColor
shapeLayer.strokeColor = line.color.cgColor
shapeLayer.lineWidth = 4
shapeLayer.position = animatedLayer.position
shapeLayer.path = path.cgPath
shapeLayer.opacity = 0
shapeLayers.append(shapeLayer)
}
And to animate the lines...
var timeOffset: Double = 0
let eachLineTime = totalTime / Double(shapeLayers.count)
for shapeLayer in shapeLayers {
CATransaction.begin()
mainLayer.addSublayer(shapeLayer)
let strokeAnimation = CABasicAnimation(keyPath: "strokeEnd")
strokeAnimation.fromValue = 0
strokeAnimation.toValue = 1
strokeAnimation.duration = eachLineTime
strokeAnimation.beginTime = CACurrentMediaTime() + timeOffset
let opacityAnimation = CABasicAnimation(keyPath: "opacity")
opacityAnimation.fromValue = 0
opacityAnimation.toValue = 1
opacityAnimation.duration = eachLineTime
opacityAnimation.beginTime = CACurrentMediaTime() + timeOffset
CATransaction.setCompletionBlock {
shapeLayer.strokeColor = UIColor.orange.cgColor
shapeLayer.opacity = 1
}
shapeLayer.add(strokeAnimation, forKey: nil)
shapeLayer.add(opacityAnimation, forKey: nil)
timeOffset += eachLineTime
CATransaction.commit()
}
I need them to be different lines because I want to change the color of each line when it finishes each animation.
I'm getting the next output in Swift Playgrounds
But I'm not getting anything when I export the video in the app.
How can I simply add a trail of the first CAShapeLayer to see the (square in this case) moving path?
How can I move the CABasicAnimation with the same timing of the CAKeyframeAnimation?