IOS, how to continuously animate the line "works" (effect of "marching ants")?

Question

I have to admit that I have no idea how to do this in iOS -

Here is the code that makes a beautiful dashed line:

Now I want this line to “run” up:

So, every second it will move up itemLength * 2.0.

Of course, it will flow from top to bottom.

So, DottedVerticalyou just have to do it completely on your own.

Really, how do you do it in iOS?

It would be great if the solution would be general and would “scroll through” everything that I suppose, a layer or a drawn thing.

They say that in the game engine this is trivial, you just animate the texture offset. Can you shift a layer or something in iOS?

What is the best way?

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@IBDesignable class DottedVertical: UIView {

    @IBInspectable var dotColor: UIColor = UIColor.faveColor

    override func draw(_ rect: CGRect) {

        // say you want 8 dots, with perfect fenceposting:
        let totalCount = 8 + 8 - 1
        let fullHeight = bounds.size.height
        let width = bounds.size.width
        let itemLength = fullHeight / CGFloat(totalCount)
        let beginFromTop = !lowerHalfOnly ? 0.0 : (fullHeight * 8.0 / 15.0)
        let top = CGPoint(x: width/2, y: beginFromTop)
        let bottom = CGPoint(x: width/2, y: fullHeight)

        let path = UIBezierPath()
        path.move(to: top)
        path.addLine(to: bottom)
        path.lineWidth = width
        let dashes: [CGFloat] = [itemLength, itemLength]
        path.setLineDash(dashes, count: dashes.count, phase: 0)
        dotColor.setStroke()
        path.stroke()
}

( - , , . "" , , .)

Answer 1

, , , Men !

! ...

@IBDesignable class DottedVertical: UIView {

    @IBInspectable var dotColor: UIColor = sfBlack6 { didSet {setup()} }

    override func layoutSubviews() { setup() }

    var s:CAShapeLayer? = nil

    func setup() {
        // say you want 8 dots, with perfect fenceposting:
        - calculate exactly as in the example in the question above -

        // marching ants...

        if (s == nil) {
            s = CAShapeLayer()
            self.layer.addSublayer(s!)
        }

        s!.strokeColor = dotColor.cgColor
        s!.fillColor = backgroundColor?.cgColor
        s!.lineWidth = width
        let ns = NSNumber(value: Double(itemLength))
        s!.lineDashPattern = [ns, ns]

        let path = CGMutablePath()
        path.addLines(between: [top, bottom])
        s!.path = path

        let anim = CABasicAnimation(keyPath: "lineDashPhase")
        anim.fromValue = 0
        anim.toValue = ns + ns
        anim.duration = 1.75 // seconds
        anim.repeatCount = Float.greatestFiniteMagnitude

        s!.add(anim, forKey: nil)

        self.layer.addSublayer(s!)
    }
}