How can I make animation with CAEmitterLayer on SwiftUI? - ios

Question

How can I convert this code to SwiftUI. It's a snow effect. I used CAEmitterLayer but I don't know how to use it in SwfitUI. There is no addSublayer in SwiftUI. Is it possible to run this code without using UIHostingController ?
let size = CGSize(width: 824.0, height: 1112.0)
let host = UIView(frame: CGRect(x: 0.0, y: 0.0, width: size.width, height: size.height))
self.view.addSubview(host)
let particlesLayer = CAEmitterLayer()
particlesLayer.frame = CGRect(x: 0.0, y: 0.0, width: size.width, height: size.height)
host.layer.addSublayer(particlesLayer)
host.layer.masksToBounds = true
particlesLayer.backgroundColor = UIColor(red: 0.0/255.0, green: 0.0/255.0, blue: 0.0/255.0, alpha: 1.0).cgColor
particlesLayer.emitterShape = .circle
particlesLayer.emitterPosition = CGPoint(x: 509.4, y: 707.7)
particlesLayer.emitterSize = CGSize(width: 1648.0, height: 1112.0)
particlesLayer.emitterMode = .surface
particlesLayer.renderMode = .oldestLast
let image1 = UIImage(named: "logo")?.cgImage
let cell1 = CAEmitterCell()
cell1.contents = image1
cell1.name = "Snow"
cell1.birthRate = 92.0
cell1.lifetime = 20.0
cell1.velocity = 59.0
cell1.velocityRange = -15.0
cell1.xAcceleration = 5.0
cell1.yAcceleration = 40.0
cell1.emissionRange = 180.0 * (.pi / 180.0)
cell1.spin = -28.6 * (.pi / 180.0)
cell1.spinRange = 57.2 * (.pi / 180.0)
cell1.scale = 0.06
cell1.scaleRange = 0.3
cell1.color = UIColor(red: 255.0/255.0, green: 255.0/255.0, blue: 255.0/255.0, alpha: 1.0).cgColor
particlesLayer.emitterCells = [cell1]

Answer 1

Here is a solution. Tested with Xcode 11.4 / iOS 13.4
struct EmitterView: UIViewRepresentable {
func makeUIView(context: Context) -> UIView {
let size = CGSize(width: 824.0, height: 1112.0)
let host = UIView(frame: CGRect(x: 0.0, y: 0.0, width: size.width, height: size.height))
let particlesLayer = CAEmitterLayer()
particlesLayer.frame = CGRect(x: 0.0, y: 0.0, width: size.width, height: size.height)
host.layer.addSublayer(particlesLayer)
host.layer.masksToBounds = true
particlesLayer.backgroundColor = UIColor(red: 0.0/255.0, green: 0.0/255.0, blue: 0.0/255.0, alpha: 1.0).cgColor
particlesLayer.emitterShape = .circle
particlesLayer.emitterPosition = CGPoint(x: 509.4, y: 707.7)
particlesLayer.emitterSize = CGSize(width: 1648.0, height: 1112.0)
particlesLayer.emitterMode = .surface
particlesLayer.renderMode = .oldestLast
let image1 = UIImage(named: "logo")?.cgImage
let cell1 = CAEmitterCell()
cell1.contents = image1
cell1.name = "Snow"
cell1.birthRate = 92.0
cell1.lifetime = 20.0
cell1.velocity = 59.0
cell1.velocityRange = -15.0
cell1.xAcceleration = 5.0
cell1.yAcceleration = 40.0
cell1.emissionRange = 180.0 * (.pi / 180.0)
cell1.spin = -28.6 * (.pi / 180.0)
cell1.spinRange = 57.2 * (.pi / 180.0)
cell1.scale = 0.06
cell1.scaleRange = 0.3
cell1.color = UIColor(red: 255.0/255.0, green: 255.0/255.0, blue: 255.0/255.0, alpha: 1.0).cgColor
particlesLayer.emitterCells = [cell1]
return host
}
func updateUIView(_ uiView: UIView, context: Context) {
}
typealias UIViewType = UIView
}
struct TestEmitterLayer: View {
var body: some View {
EmitterView() // << usage !!
}
}