How to create animation inside CGContext

Question

I have a circle and I want to make it pulsate.

func drawCircle(context: CGContext) {
    let circle = CGRect(x: circleX, y: circleY, width: circleDiameter, height: circleDiameter)
    context.setFillColor(UIColor.systemPink.cgColor)
    context.addEllipse(in: circle)
}

But I just don't understand how to do it inside CGContext

You probably need to look at CoreAnimation, Does this help you: https://stackoverflow.com/a/67611170/1619193 — Shawn Frank, Mar 14 '22 at 11:11
@ShawnFrank Yes, I found this issue. But the fact is that I need to do more at a lower level than in that question. Thanks! — errorka, Mar 14 '22 at 11:15

score 1 · Accepted Answer · answered Mar 14 '22 at 11:49

1

Here is one way you can do it using CoreAnimation:

func drawCircle(context: CGContext) {
    context.setFillColor(UIColor.systemPink.cgColor)
    
    context.addEllipse(in: CGRect(x: bounds.origin.x,
                                  y: bounds.origin.y,
                                  width: bounds.width,
                                  height: bounds.height))
    
    context.fillPath()
    
    // Using CoreAnimation
    let animation = CABasicAnimation(keyPath: "transform.scale")
    animation.repeatCount = .infinity
    animation.duration = 2
    animation.toValue = 1.5
    animation.timingFunction = CAMediaTimingFunction(name: .easeInEaseOut)
    animation.autoreverses = true
    
    layer.add(animation, forKey: nil)
}

answered Mar 14 '22 at 11:49

Shawn Frank

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Thanks for your reply. But the problem is that in my class there is no access to `layer.add...`. My class is responsible for rendering. – errorka Mar 14 '22 at 11:55
And in it I have to use `CoreGraphics` – errorka Mar 14 '22 at 11:56
@errorka - what is your class, maybe you can put basic code of your class and where the pulse will be rendered, how it will be used etc ? – Shawn Frank Mar 14 '22 at 15:35
I decided to forward the layer to my class and do as you answered – errorka Mar 15 '22 at 12:36

How to create animation inside CGContext

1 Answers1