另一种解决方案是移动框架以修改ZStack而不是Rectangle

struct ContentView: View {
    @State private var overlayUIScreen: Bool = false

    var body: some View {
        ZStack {
            if overlayUIScreen {
                Rectangle()
                    .edgesIgnoringSafeArea(.top)
                    .foregroundColor(Color.gray)
                    .transition(.opacity)
            }

            Button("Overlay?") {
                withAnimation {
                    self.overlayUIScreen.toggle()
                }
            }
        }
        .frame(width: UIScreen.main.bounds.size.width,height: UIScreen.main.bounds.size.height)
    }
}

一种解决方法是将您的视图包含在层次结构中，并将其不透明性归因于@State私有变量，如下所示：

struct ContentView: View {
    @State private var overlayOpacity: Double = 0.0

    var body: some View {
        ZStack {

            Rectangle()
                 .edgesIgnoringSafeArea(.top)
                 .frame(width: UIScreen.main.bounds.size.width,height: UIScreen.main.bounds.size.height)

                 .opacity(overlayOpacity)

                 .foregroundColor(Color.gray)

            Button("Overlay?") {
                withAnimation {
                    if self.overlayOpacity == 0.0 {
                        self.overlayOpacity = 1.0
                    } else {
                        self.overlayOpacity = 0.0
                    }
                }
            }

        }  .transition(.opacity)
    }
}