Source code for the article 'Activity Indicator in SwiftUI' (https://jetrockets.pro/blog/activity-indicator-in-swiftui)

ActivityIndicator.swift

private let kPreviewBackground = Color(red: 237/255.0, green: 85/255.0, blue: 101/255.0)

struct ActivityIndicator: View {
    
    @State private var isAnimating: Bool = false
    
    var body: some View {
        GeometryReader { (geometry: GeometryProxy) in
            ForEach(0..<5) { index in
                Group {
                    Circle()
                        .frame(width: geometry.size.width / 5, height: geometry.size.height / 5)
                        .scaleEffect(!self.isAnimating ? 1 - CGFloat(index) / 5 : 0.2 + CGFloat(index) / 5)
                        .offset(y: geometry.size.width / 10 - geometry.size.height / 2)
                }.frame(width: geometry.size.width, height: geometry.size.height)
                    .rotationEffect(!self.isAnimating ? .degrees(0) : .degrees(360))
                    .animation(Animation
                        .timingCurve(0.5, 0.15 + Double(index) / 5, 0.25, 1, duration: 1.5)
                        .repeatForever(autoreverses: false))
            }
        }.aspectRatio(1, contentMode: .fit)
            .onAppear {
                self.isAnimating = true
            }
    }
    
}

ContentView.swift

private let kPreviewBackground = Color(red: 237/255.0, green: 85/255.0, blue: 101/255.0)

struct ContentView: View {
    var body: some View {
        ZStack {
            kPreviewBackground
                .edgesIgnoringSafeArea(.all)
            
            VStack {
                ActivityIndicator()
                    .frame(width: 50, height: 50)
            }.foregroundColor(Color.white)
        }
    }
}