SharedPreferences в Flutter

Question

Я делаю простенькое приложение, в котором пользователь может зарегистрироваться и совершить вход. Есть 3 основные страницы: Вход:

import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:fluttertoast/fluttertoast.dart';
import 'package:tbench/pages/home.dart';
import 'package:tbench/pages/registration.dart';

class LoginScreen extends StatefulWidget {
  const LoginScreen({Key? key}) : super(key: key);

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

class _LoginScreenState extends State<LoginScreen> {

  final _formKey = GlobalKey<FormState>();

  final TextEditingController emailController = TextEditingController();
  final TextEditingController passwordController = TextEditingController();

  final _auth = FirebaseAuth.instance;


  @override
  Widget build(BuildContext context) {

    //email field
    final emailField = TextFormField(
      autofocus: false,
      controller: emailController,
      keyboardType: TextInputType.emailAddress,
      validator: (value)
      {
        if (value!.isEmpty)
        {
          return ("Please, enter your E-mail");
        }

        if (!RegExp("^[a-zA-Z0-9+_.-]+@[a-zA-Z0-9.-]+.[a-z]").hasMatch(value))
        {
          return ("Please, enter a valid E-mail");
        }

        return null;
      },
      onSaved: (value)
      {
        emailController.text = value!;
      },
      textInputAction: TextInputAction.next,
      decoration: InputDecoration(
        prefixIcon: const Icon(Icons.mail),
        contentPadding: const EdgeInsets.fromLTRB(20, 15, 20, 15),
        hintText: "E-mail",
        border: OutlineInputBorder(
          borderRadius: BorderRadius.circular(10),
        ),
      ),
    );

    //password field
    final passwordField = TextFormField(
      autofocus: false,
      controller: passwordController,
      obscureText: true,
      validator: (value)
      {
        RegExp regexp = new RegExp(r'^.{6,}$');
        if (value!.isEmpty)
        {
          return ("Please, enter your Password");
        }

        if (!regexp.hasMatch(value))
        {
          return ("Min 6 characters");
        }
      },
      onSaved: (value)
      {
        passwordController.text = value!;
      },
      textInputAction: TextInputAction.done,
      decoration: InputDecoration(
        prefixIcon: const Icon(Icons.vpn_key),
        contentPadding: const EdgeInsets.fromLTRB(20, 15, 20, 15),
        hintText: "Password",
        border: OutlineInputBorder(
          borderRadius: BorderRadius.circular(10),
        ),
      ),
    );

    //login button
    final loginButton = Material(
      elevation: 5,
      borderRadius: BorderRadius.circular(30),
      color: Colors.blueAccent,
      child: MaterialButton(
        padding: const EdgeInsets.fromLTRB(20, 15, 20, 15),
        minWidth: MediaQuery.of(context).size.width,
        onPressed: () {
          signIn(emailController.text, passwordController.text);
        },
        child: const Text("Login", textAlign: TextAlign.center,
        style: TextStyle(
            fontSize: 20, color: Colors.white, fontWeight: FontWeight.bold),
        )),
    );

    return Scaffold(
      backgroundColor: Colors.white,
      body: Center(
        child: SingleChildScrollView(
          child: Container(
            color: Colors.white,
            child: Padding(
              padding: const EdgeInsets.all(36.0),
              child: Form(
                key: _formKey,
                child: Column(
                  mainAxisAlignment: MainAxisAlignment.center,
                  crossAxisAlignment: CrossAxisAlignment.center,
                  children: <Widget>[
                    
                    SizedBox(
                      height: 200,
                      child: Image.asset("assets/logo_icon.png",
                          fit: BoxFit.contain,)
                    ),
                    const SizedBox(height: 45),
                    emailField,
                    const SizedBox(height: 20),
                    passwordField,
                    const SizedBox(height: 35),
                    loginButton,
                    const SizedBox(height: 15),
                    Row (
                      mainAxisAlignment: MainAxisAlignment.center,
                      children: <Widget>[
                        const Text("Don't have an account? "),
                        GestureDetector(
                          onTap: () {
                            Navigator.push(
                                context,
                                MaterialPageRoute(
                                    builder: (context) =>
                                        RegistrationScreen()));
                          },
                          child: const Text(
                            "Sign Up",
                            style: TextStyle(
                              color: Colors.blueAccent,
                              fontWeight: FontWeight.bold,
                              fontSize: 15),
                          ),
                        )
                      ],
                    )
                  ],
                ),
              ),
            ),
          ),
        ),
      )
    );
  }


  void signIn(String email, String password) async
  {
    if(_formKey.currentState!.validate()) {
      await _auth
          .signInWithEmailAndPassword(email: email, password: password)
          .then((uid) => {
            Fluttertoast.showToast(msg: "Login Successful"),
            Navigator.of(context).pushReplacement(MaterialPageRoute(builder: (context) => HomeScreen())),
      }).catchError((e)
      {
        Fluttertoast.showToast(msg: e!.message);
      });
    }
  }


}

Регистрация:

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:fluttertoast/fluttertoast.dart';
import 'package:tbench/model/user_model.dart';
import 'package:tbench/pages/home.dart';

class RegistrationScreen extends StatefulWidget {
  const RegistrationScreen({Key? key}) : super(key: key);

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

class _RegistrationScreen extends State<RegistrationScreen> {

  final _formKey = GlobalKey<FormState>();

  final fullNameEditingController = TextEditingController();
  final userNameEditingController = TextEditingController();
  final emailEditingController = TextEditingController();
  final passwordEditingController = TextEditingController();
  final confirmPasswordEditingController = TextEditingController();

  final _auth = FirebaseAuth.instance;

  @override
  Widget build(BuildContext context) {

    //full name field
    final fullNameField = TextFormField(
      autofocus: false,
      controller: fullNameEditingController,
      keyboardType: TextInputType.name,
      validator: (value)
      {
        RegExp regexp = new RegExp(r'^.{3,}$');
        if (value!.isEmpty)
        {
          return ("Please, enter your Full Name");
        }

        if (!regexp.hasMatch(value))
        {
          return ("Min 3 characters");
        }

        return null;
      },
      onSaved: (value)
      {
        fullNameEditingController.text = value!;
      },
      textInputAction: TextInputAction.next,
      decoration: InputDecoration(
        prefixIcon: const Icon(Icons.account_circle),
        contentPadding: const EdgeInsets.fromLTRB(20, 15, 20, 15),
        hintText: "Full Name",
        border: OutlineInputBorder(
          borderRadius: BorderRadius.circular(10),
        ),
      ),
    );

    //username field
    final userNameField = TextFormField(
      autofocus: false,
      controller: userNameEditingController,
      keyboardType: TextInputType.name,
      validator: (value)
      {
        RegExp regexp = new RegExp(r'^.{3,}$');
        if (value!.isEmpty)
        {
          return ("Please, enter your Username");
        }

        if (!regexp.hasMatch(value))
        {
          return ("Min 3 characters");
        }

        return null;
      },
      onSaved: (value)
      {
        userNameEditingController.text = value!;
      },
      textInputAction: TextInputAction.next,
      decoration: InputDecoration(
        prefixIcon: const Icon(Icons.account_circle),
        contentPadding: const EdgeInsets.fromLTRB(20, 15, 20, 15),
        hintText: "Username",
        border: OutlineInputBorder(
          borderRadius: BorderRadius.circular(10),
        ),
      ),
    );

    //username field
    final emailField = TextFormField(
      autofocus: false,
      controller: emailEditingController,
      keyboardType: TextInputType.emailAddress,
      validator: (value)
      {
        if (value!.isEmpty)
        {
          return ("Please, enter your E-mail");
        }

        if (!RegExp("^[a-zA-Z0-9+_.-]+@[a-zA-Z0-9.-]+.[a-z]").hasMatch(value))
        {
          return ("Please, enter a valid E-mail");
        }

        return null;
      },
      onSaved: (value)
      {
        emailEditingController.text = value!;
      },
      textInputAction: TextInputAction.next,
      decoration: InputDecoration(
        prefixIcon: const Icon(Icons.mail),
        contentPadding: const EdgeInsets.fromLTRB(20, 15, 20, 15),
        hintText: "E-mail",
        border: OutlineInputBorder(
          borderRadius: BorderRadius.circular(10),
        ),
      ),
    );

    //password field
    final passwordField = TextFormField(
      autofocus: false,
      controller: passwordEditingController,
      obscureText: true,
      validator: (value)
      {
        RegExp regexp = new RegExp(r'^.{6,}$');
        if (value!.isEmpty)
        {
          return ("Please, enter your Password");
        }

        if (!regexp.hasMatch(value))
        {
          return ("Min 6 characters");
        }
      },
      onSaved: (value)
      {
        passwordEditingController.text = value!;
      },
      textInputAction: TextInputAction.next,
      decoration: InputDecoration(
        prefixIcon: const Icon(Icons.vpn_key),
        contentPadding: const EdgeInsets.fromLTRB(20, 15, 20, 15),
        hintText: "Password",
        border: OutlineInputBorder(
          borderRadius: BorderRadius.circular(10),
        ),
      ),
    );

    //confirm password field
    final confirmPasswordField = TextFormField(
      autofocus: false,
      controller: confirmPasswordEditingController,
      obscureText: true,
      validator: (value)
      {
        if (confirmPasswordEditingController.text != passwordEditingController.text)
        {
          return ("Password mismatch");
        }

        return null;
      },
      onSaved: (value)
      {
        confirmPasswordEditingController.text = value!;
      },
      textInputAction: TextInputAction.done,
      decoration: InputDecoration(
        prefixIcon: const Icon(Icons.vpn_key),
        contentPadding: const EdgeInsets.fromLTRB(20, 15, 20, 15),
        hintText: "Confirm password",
        border: OutlineInputBorder(
          borderRadius: BorderRadius.circular(10),
        ),
      ),
    );

    //signUp button
    final signUpButton = Material(
      elevation: 5,
      borderRadius: BorderRadius.circular(30),
      color: Colors.blueAccent,
      child: MaterialButton(
          padding: const EdgeInsets.fromLTRB(20, 15, 20, 15),
          minWidth: MediaQuery.of(context).size.width,
          onPressed: () {
            signUp(emailEditingController.text, passwordEditingController.text);
          },
          child: const Text("Sign Up", textAlign: TextAlign.center,
            style: TextStyle(
                fontSize: 20, color: Colors.white, fontWeight: FontWeight.bold),
          )),
    );

    return Scaffold(
        backgroundColor: Colors.white,
        appBar: AppBar(
          backgroundColor: Colors.transparent,
          elevation: 0,
          leading: IconButton(
            icon: const Icon(Icons.arrow_back, color: Colors.blueAccent,),
            onPressed: () {
              Navigator.of(context).pop();
            },
          ),
        ),
        body: Center(
          child: SingleChildScrollView(
            child: Container(
              color: Colors.white,
              child: Padding(
                padding: const EdgeInsets.all(36.0),
                child: Form(
                  key: _formKey,
                  child: Column(
                    mainAxisAlignment: MainAxisAlignment.center,
                    crossAxisAlignment: CrossAxisAlignment.center,
                    children: <Widget>[

                      fullNameField,
                      const SizedBox(height: 20),
                      userNameField,
                      const SizedBox(height: 20),
                      emailField,
                      const SizedBox(height: 20),
                      passwordField,
                      const SizedBox(height: 20),
                      confirmPasswordField,
                      const SizedBox(height: 35),
                      signUpButton,
                      const SizedBox(height: 15),

                    ],
                  ),
                ),
              ),
            ),
          ),
        )
    );
  }

  void signUp(String email, String password) async
  {
    if (_formKey.currentState!.validate()) {
      await _auth
          .createUserWithEmailAndPassword(email: email, password: password)
          .then((value) => {
            postDetailsToFirestore()
      }).catchError((e)
      {
        Fluttertoast.showToast(msg: e!.message);
      });
    }
  }

  postDetailsToFirestore() async
  {
    //calling firestore
    //calling user model
    //calling these values

    FirebaseFirestore firebaseFirestore = FirebaseFirestore.instance;
    User? user = _auth.currentUser;

    UserModel userModel = UserModel();

    //writing values
    userModel.uid = user!.uid;
    userModel.email = user.email;
    userModel.fullName = fullNameEditingController.text;
    userModel.userName = userNameEditingController.text;

    await firebaseFirestore
        .collection("users")
        .doc(user.uid)
        .set(userModel.toMap());
    Fluttertoast.showToast(msg: "Account created successfully");

    Navigator.pushAndRemoveUntil(
        (context),
        MaterialPageRoute(builder: (context) => HomeScreen()),
        (route) => false);

  }
}

И главная страница:

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:tbench/model/user_model.dart';
import 'package:tbench/pages/login.dart';

class HomeScreen extends StatefulWidget {
  const HomeScreen({Key? key}) : super(key: key);

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


class _HomeScreen extends State<HomeScreen> {

  User? user = FirebaseAuth.instance.currentUser;
  UserModel loggedInUser = UserModel();

  @override
  void initState() {
    super.initState();
    FirebaseFirestore.instance
        .collection("users")
        .doc(user!.uid)
        .get()
        .then((value) {
      this.loggedInUser = UserModel.fromMap(value.data());
      setState(() {

      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("Welcome"),
        centerTitle: true,
      ),
      body: Center(
        child: Padding(
          padding: const EdgeInsets.all(20),
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            crossAxisAlignment: CrossAxisAlignment.center,
            children: <Widget>[
              SizedBox(height: 150,
                child: Image.asset("assets/logo_icon.png", fit: BoxFit.contain),
              ),
              const Text(
                "Welcome Back",
                style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold),
              ),
              const SizedBox(height: 10),
              Text(
                  "${loggedInUser.fullName}",
                  style: const TextStyle(
                    color: Colors.black54,
                    fontWeight: FontWeight.w500,
                  )),
              Text(
                  "${loggedInUser.email}",
                  style: const TextStyle(
                    color: Colors.black54,
                    fontWeight: FontWeight.w500,
                  )),
              const SizedBox(height: 15),
              ActionChip(label: const Text("Logout"), onPressed: () {
                logout(context);
              })
            ],
          ),
        ),
      ),
    );
  }

  Future<void> logout(BuildContext context) async
  {
    await FirebaseAuth.instance.signOut();
    Navigator.of(context).pushReplacement(
    MaterialPageRoute(builder: (context) => LoginScreen()));
  }

}

На главной странице также можно выйти на страницу входа. И есть файл main.dart:

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();

  runApp(MyApp());
}

class MyApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'tBench',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const LoginScreen(),
    );
  }
}

Но проблема в том, что пользователь, совершивший вход, после закрытия приложения снова попадает на страницу входа. Я так понимаю, нужно использовать SharedPreferences, но я не совсем понимаю, как именно и где. Помогите, пожалуйста :(

БЛОГ НА HUSL

SharedPreferences в Flutter

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