Just testing out Firebase Auth with Flutter for web

main.dart

import 'package:firebase/firebase.dart' as firebase;
import 'package:firebase_auth/firebase_auth.dart' as firebaseAuth;
import 'package:firebase_core/firebase_core.dart';
import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Firebase Auth Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  User _user;
  bool _isAuthReady = false;

  final Future<FirebaseApp> _initFirebase = Firebase.initializeApp();

  Future<void> _signin() async {
    final auth = firebaseAuth.FirebaseAuth.instance;
    await auth.signInWithEmailAndPassword(
      email: 'test@example.com',
      password: 'example1',
    );
    final user = User(
      uid: auth.currentUser.uid,
      email: auth.currentUser.email,
    );
    setState(() {
      _user = user;
    });
  }

  Future<void> _signOut() async {
    final auth = firebaseAuth.FirebaseAuth.instance;
    await auth.signOut();
    setState(() {
      _user = null;
    });
    print('Signed out');
  }

  Future<void> _getUser() async {
    final firebaseUser =
        await firebase.auth(firebase.app()).onAuthStateChanged.first;
    final user = firebaseUser != null
        ? User(uid: firebaseUser.uid, email: firebaseUser.email)
        : null;
    setState(() {
      _isAuthReady = true;
      _user = user;
    });
  }

  Future<void> _checkUser() async {
    final auth = firebaseAuth.FirebaseAuth.instance;
    print(auth.currentUser);
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        child: FutureBuilder(
          future: _initFirebase,
          builder: (context, snapshot) {
            if (snapshot.hasError) {
              // Error
              return Text('Error!');
            }

            if (snapshot.connectionState == ConnectionState.done) {
              // Success
              return Column(
                children: [
                  RaisedButton(
                    onPressed: _signin,
                    child: Text('Sign in'),
                  ),
                  RaisedButton(
                    onPressed: _checkUser,
                    child: Text('Check User'),
                  ),
                  RaisedButton(
                    onPressed: _signOut,
                    child: Text('Sign out'),
                  ),
                  Text(_isAuthReady
                      ? _user?.email ?? 'No User'
                      : 'Loading Auth'),
                ],
              );
            }

            // Loading
            return Text('Loading');
          },
        ),
      ),
    );
  }
}

class User {
  User({
    @required this.uid,
    @required this.email,
  });

  final String uid;
  final String email;
}