How to prevent the user from returning to the login screen after logging into the flutter?

Question

I have the following login widget that after the request is successfully made, it adds on the navigation stack to the home screen and removes the login screen.

If I try to get back from home screen to login the app is minimized. However, when I open again the app opens the login screen.

In my main.dart is checked if it has a token. If it does, it is directed to the home screen. If not, to the login screen.

  checkHome() async {
    // Read value
    String token = await storage.read(key: 'token');

    return token;
  }

  @override
  void initState(){
    super.initState();
    checkHome();
  }


  @override
  Widget build(BuildContext context) {

    /// Chamada para solucionar o método.
    /// Nele também é acionado o `then()` que é
    /// que é onde pode ser capturado o retorno do futuro.
    checkHome().then((token) {
      temToken = token != null;
    });

    return MaterialApp(
      title: 'Cadê meu pet?',
      theme: ThemeData(primarySwatch: Colors.yellow),
      /// Declaração do ternário para escolher qual page exibir
      home: temToken ? HomePage() : LoginPage(),
      routes: routes
    );
  }
}

This is the way I handle the navigation stack on login:

if (response.statusCode == 202) {
      Map<String, dynamic> map = json.decode(response.body);
      // Write values
      await storage.write(key: 'token', value: map['token']);
      await storage.write(key: 'foto', value: map['foto']);
      await storage.write(key: 'nomeUsuario', value: map['nomeUsuario']);
      Navigator.pushNamed(context, '/home');
      Navigator.popUntil(context, ModalRoute.withName('/login'));
 }

My setting:

I have a token, so I’m on the home screen; I click on the button "back" android; The app is minimized; I open the app again; The login screen is displayed.

By possessing token, the expected is that when the app is minimized, when returning open the home screen.

Answer 1

You can clear the navigation stack after successfully logging in.

Use your Navigator this way for the new screen:

Navigator.of(context).pushAndRemoveUntil(MaterialPageRoute(builder: (context)=>HomePage()),(Route<dynamic> route) => false);

This way you clear the navigation and if the user tries to come back will minimize the application.

Answer 2

Your structure doesn’t work because you’re working with a Future and you’re not doing the right thing... You can try two ways

1st form

Add the setState() and see if it works as you wish

  checkHome().then((token) {
    setState((){
      temToken = token != null;
    });
  });

2nd form

Make use of the FutureBuilder()

Future<bool> checkHome() async {
    String token = await storage.read(key: 'token');
    return token != null;
  }

  @override
  Widget build(BuildContext context) {

    return MaterialApp(
      title: 'Cadê meu pet?',
      theme: ThemeData(primarySwatch: Colors.yellow),
      /// Declaração do ternário para escolher qual page exibir
      home: FutureBuilder(
        future: checkHome(),
        builder: (context, snapshot){
          if (!snpashot.hasData)
            return Center(child: CircularProgressIndicator());

          return snpashot.data ? HomePage() : LoginPage();
        }
      ),
      routes: routes
    );
  }