实现一个扫描二维码的动画效果，然而SwiftUI中没有提供CABasicAnimation 动画方法，该如何实现这种效果？先弄清楚什么关键帧动画，简单的说就是指视图从起点至终点的状态变化，可以是形状、位置、透明度等等

本文提供了一种方法Timer + offset + animation+@State，来实现位移变化

struct HomePage: View {@State var openScanQR = false@State var scanResult:String = ""@State var isAnimated = false@State var timer = Timer.publish(every: 3, on: .main, in: .common).autoconnect()var body: some View {VStack{}.ignoresSafeArea(edges: .top).fullScreenCover(isPresented: $openScanQR, content: {ScannerView(result: $scanResult).overlay(ZStack{Color.black.opacity(0.5)Image("scan_round").resizable().renderingMode(.template).aspectRatio(contentMode: .fill).foregroundColor(.blue).frame(height: UIScreen.main.bounds.width - 80).padding(.horizontal, 40)Image("scan_line").resizable().renderingMode(.template).aspectRatio(contentMode: .fill).foregroundColor(.blue).frame(height: 2).padding(.horizontal, 40).offset(y: !isAnimated ? -(UIScreen.main.bounds.width - 80)/2:  (UIScreen.main.bounds.width - 80)/2).animation(.easeOut(duration: 3), value: isAnimated)}).edgesIgnoringSafeArea(.all)}).onReceive(timer, perform: { _ inwithAnimation {isAnimated.toggle()}}).background(Color.background_color).edgesIgnoringSafeArea(.top)}
}