FutureBuilder fire #11956

    return new FutureBuilder<FirebaseUser>(future: _initAsync(),
      builder: (BuildContext context, AsyncSnapshot<FirebaseUser> snapshot) {
        switch (snapshot.connectionState) {
          case ConnectionState.none:
            return new Text('Press button to start');
          case ConnectionState.waiting:
            return new Text('Awaiting result...');
          default:
            if (snapshot.hasError)
              return new Text('Error: ${snapshot.error}');
            else
              if(snapshot.data == null){
                return new Login();
              }else{
                return new Home();
              }

        }
      },

class _LoginState extends State<Login> {

  //Auth

  final localAuth = new LocalAuthentication();
  final firebaseAuth = FirebaseAuth.instance;

  //SharePreferences

  final String userSharePreference = "User";
  final String passwordSharePreference = "Password";

  //Log in

  String user;
  String password;

  _logIn() async {

    firebaseAuth.signInWithEmailAndPassword(email: user, password: password)
        .then((FirebaseUser user){
          Navigator.of(context).push(new MaterialPageRoute<Null>(builder: (BuildContext context) {
                return new Home();
              }));
        })
        .catchError((e){
          Scaffold.of(context).showSnackBar(new SnackBar(content: new Text(e.toString())));
    });
  }

  _logInFingerprint() async{

    SharedPreferences prefs = await SharedPreferences.getInstance();
    await localAuth.authenticateWithBiometrics(localizedReason: "FINGERPRINT")
      .then((bool result){

        setState((){
          user = prefs.getString(userSharePreference);
          password = prefs.getString(passwordSharePreference);
        });

        firebaseAuth.signInWithEmailAndPassword(email: user, password: password)
            .then((FirebaseUser user){
              Navigator.of(context).push(
                  new MaterialPageRoute<Null>(builder: (BuildContext context) {
                    return new Home();
                  }));
            })
            .catchError((e){
              Scaffold.of(context).showSnackBar(new SnackBar(content: new Text(e.toString())));
            });
      }).catchError((e){
      Scaffold.of(context).showSnackBar(new SnackBar(content: new Text(e.toString())));
    });
  }


  _showPassword() {}

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
        body: new Container(
            color: Colors.indigo,
            child: new Center(
                child: new Padding(
                    padding: new EdgeInsets.all(10.0),
                    child: new Card(
                      child: new Padding(
                        padding:
                            new EdgeInsets.fromLTRB(15.0, 10.0, 15.0, 10.0),
                        child: new Column(
                          mainAxisSize: MainAxisSize.min,
                          children: <Widget>[
                            new FlutterLogo(
                              size: 100.0,
                            ),
                            new TextFormField(
                              decoration: new InputDecoration(
                                hintText: "Insert user",
                                labelText: "User",
                                helperText: "Insert a valid user",
                              ),
                            ),
                            new TextFormField(
                              decoration: new InputDecoration(
                                  hintText: "Insert Password",
                                  labelText: "Password",
                                  helperText: "Insert a valid Password"),
                              obscureText: true,
                            ),
                            new ButtonTheme.bar(
                              // make buttons use the appropriate styles for cards
                              child: new ButtonBar(
                                children: <Widget>[
                                  new FlatButton(
                                    child: const Text('FINGERPRINT'),
                                    onPressed: _logInFingerprint,
                                    color: Colors.teal,
                                    textColor: Colors.white,
                                  ),
                                  new FlatButton(
                                    child: const Text('LOG IN'),
                                    onPressed: _logIn,
                                    color: Colors.blue,
                                    textColor: Colors.white,
                                  ),
                                ],
                              ),
                            ),
                          ],
                        ),
                      ),
                    )))));
  }
}```