为什么后退按钮在Flutter应用程序中不起作用？

Question

“后退”按钮不执行任何操作。 我猜问题出在onGenerateRoute。 我没有任何代码可以对后退按钮做任何事情。

class MyApp extends StatelessWidget {

  static final GlobalKey<NavigatorState> navigatorKey = new GlobalKey<NavigatorState>();

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'MyApp',
      theme: ThemeData(
        primarySwatch: Colors.pink,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      navigatorKey: navigatorKey,
      onGenerateRoute: (settings) {
        var routes = <String, WidgetBuilder>{
          '/login': (context) => LoginPage(loginFailed: settings.arguments),
          '/main': (context) => MainPage(),
          '/loading': (context) => LoadingPage(credentials: settings.arguments),
          '/addAppointment': (context) => AddAppointmentPage(),
        };

        WidgetBuilder builder = routes[settings.name] ?? routes['/loading'];
        return MaterialPageRoute(builder: builder);
      },
    );
  }
}