我从一个在有状态小部件中创建的顶层scaffold开始。应用程序会自动导航到回家路线，并且appbar减去后退按钮会正确显示。
下面是主代码

Widget build(BuildContext context) {
  return MultiProvider(
    providers: [
      ChangeNotifierProvider<MyAquariumManagerModel>(
        create: (_) => MyAquariumManagerModel(manageSession),
      ),
      ChangeNotifierProvider<MyAquariumManagerFacilityModel>(
        create: (_) => MyAquariumManagerFacilityModel(manageSession),
      ),
      ChangeNotifierProvider<MyAquariumManagerTanksModel>(
        create: (_) => MyAquariumManagerTanksModel(manageSession),
      ),
      ChangeNotifierProvider<MyAquariumManagerSearchModel>(
        create: (_) => MyAquariumManagerSearchModel(manageSession),
      ),
    ],
    child: MaterialApp(
      title: kProgramName,
      theme: aquarium_manager_theme,
      home: ScaffoldController(),
    ),
  );
}

和顶级ScaffoldController

Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      title: const Text(kProgramName),
    ),
  body: Navigator(
      initialRoute: '/',
      onGenerateRoute: (RouteSettings settings) {
        WidgetBuilder builder;
        switch (settings.name) {
          case '/':
            builder = (BuildContext _) => MyAquariumManagerLoginController(); <-there is no other scaffold here; it depends on the top-level one (this one right here)
            break;
          case '/homescreen':
            builder = (BuildContext _) => AquariumManagerHomeScreenController(); <- there is also no other scaffold here, we never navigate here. MyAquariumManagerLoginController just returns the widgets of this controller.
            break;
          case '/searchscreen':
            builder = (BuildContext _) => MyAquariumManagerSearchController();
            break;
          case '/facilitiesscreen':
            builder = (BuildContext _) => MyAquariumManagerFacilitiesController();
            break;
          case '/tanksscreen':
            builder = (BuildContext _) => MyAquariumManagerTankController(arguments: {
              'incomingRack_Fk': null,
              'incomingTankPosition': null,
            },);
            break;
          default:
            throw Exception('Invalid route: ${settings.name}');
        }
        return MaterialPageRoute(builder: builder, settings: settings);
      },
    ),
  );
}

我以这种方式导航到其他屏幕

Navigator.push(
  context,
  MaterialPageRoute(
    builder: (context) => MyAquariumManagerFacilitiesController(),
    settings: RouteSettings(name: '/facilitiesscreen'),
  ),
)

顶层的appbar仍然存在，但没有后退按钮。其中一些屏幕恰好有自己的scaffold，它们的appbar出现在顶层scaffold的appbar下面，但是这个appbar确实显示了一个后退按钮。
理想情况下，我希望从各个路径中移除脚手架，只保留顶层脚手架，但如何让它显示自己的后退按钮？
我尝试强制按钮出现，然后弹出路由栈，我总是得到一个黑屏，所以出于某种原因，顶层脚手架不知道路由栈上有什么，但我不知道为什么。对于少数有自己的scaffold的路由，它们的返回按钮可以工作，所以在某些地方，它知道堆栈上有哪些路由。