根据Apple's Docs，MenuBarExtra符合Scene-这意味着你可以使用ScenePhase的Environment变量在MenuBarExtra每次进入前台或后台时调用一些东西。https://www.hackingwithswift.com/quick-start/swiftui/how-to-detect-when-your-app-moves-to-the-background-or-foreground-with-scenephase。示例用法：

@main
struct AppWithMenuBarExtra: App {
@Environment(\.scenePhase) var scenePhase // <-- HERE! This will give you the values

    var body: some Scene {
        WindowGroup {
            ContentView()
        }
        MenuBarExtra(
            "App Menu Bar Extra", systemImage: "star")
        {
            StatusMenu()
.onChange(of: scenePhase) { newPhase in //<-- HERE TOO! This modifier allows you to detect change of scene.
                if newPhase == .inactive {
                    //Code for moved to inactive
                    print("Moved to inactive")
                } else if newPhase == .active {
                    //Code for moved to foreground
                    print("Moved to foreground - now active")
                    //This is where you would want to change your text
                } else if newPhase == .background {
                    //Code for moved to background
                    print("Moved to background")
                }
            }
        }
    }
}