How Flutter Keeps Logged In

Prerequisites/What you want to achieve

Currently, I am learning about application development using Flutter+Firebase.
We would like to implement the following features as a consistent login feature:

Transition to the login page and log in only when logging in for the first time
Unless you log out, you will not transition to the login page even if you open the app after you exit the app

I did some research in my own way and tried them, but I didn't go to the login page in the first place.
The code I tried is the main code below.

How can we implement these functions as a concrete method?
Also, I am currently implementing features using Firebase's Email and Password, but is this a common way to implement these features even for Google and Facebook logins?

I am a beginner at Flutter, so I would appreciate it if you could let me know.

What is currently being implemented

Login with FirebaseAuth
Database using FirebaseCloudStore

Tried

Verifying Login Status Using CurrentUser in FirebaseAuth

Supplementary information (for example, FW/Tool Version)

what you used

FirebaseAuth
FirebaseCloudStore

class MyApp extensions StatelessWidget{
  // This widget is the root of your application.

  final UserState user=UserState();

  @override
  Widget build (BuildContext context) {
    return ChangeNotifierProvider<UserState>.value(
        value —user,
        child —MaterialApp(
          // Hide Debug Labels
          debugShowCheckedModeBanner: false,
          title: 'Flutter Demo',
          theme: ThemeData(
            primarySwitch:Colors.blue,
            visualDensity —VisualDensity.adaptivePlatformDensity,
          ),
          home —LoginPage(),
          initialRoute: "/",
          routes —<String, WidgetBuilder>{
//            " / " : (BuildContext context) = > LoginPage(),
            AddRecord.routeName: (BuildContext context) = > AddRecord(),
            "/login" : (BuildContext context) = > LoginPage(),
            "/home": (BuildContext context) = > PageManager()
          },
        )
    );
  }
}

class LoginCheck extensions StatefulWidget {
  LoginCheck ({Key}):super(key:key);

  @override
  _LoginCheckState createState()=>_LoginCheckState();

}

class_LoginCheckState extensions State<LoginCheck>{

  @override
  void initState() {
    super.initState();
    checkUser();

    // TODO:implementation initState


  }
  void checkUser()async {
    final UserState userState=Provider.of<UserState>(context);
    final currentUser=wait FirebaseAuth.instance.currentUser();
    print(currentUser);
    if(currentUser==null){
      Navigator.pushReplacementNamed(context, "/login");
    } else {
      userState.setUser(currentUser);
      Navigator.pushReplacementNamed(context, "/home");
    }
  }
  @override
  Widget build (BuildContext context) {
    // TODO:implementation build
    US>return Scaffold(
      body: Center(
        child —Container(
          child: Text("Loading..."),
        ),
      ),
    );
  }
}

firebase flutter dart

2022-09-30 14:39

1 Answers

Do you initialize Firebase in the first place?
If you use FirebaseSDK, you must do Firebase.initialize when starting the application

import'package:flutter/material.dart';

// Import the firebase_core plugin
import 'package:firebase_core/firebase_core.dart';

void main() {
  WidgetsFlutterBinding.ensureInitialized();
  runApp(App());
}

class App extensions StatelessWidget {
  // Create the initialization Future outside of `build`:
  final Future<FirebaseApp>_initialization=Firebase.initializeApp();

  @override
  Widget build (BuildContext context) {
    US>return FutureBuilder(
      // Initialize FlutterFire:
      future:_initialization,
      builder: (context, snapshot) {
        // Check for errors
        if(snapshot.hasError){
          return SomethingWentWrong(); // Error Page
        }

        // Once complete, show your application
        if(snapshot.connectionState==ConnectionState.done){
        // Put the main body of the app here
          return MyAwesomeApp();
        }

        // Otherwise, show something while waiting for initialization to complete
        return Loading(); // Progress Indicator
      },
    );
  }
}

https://firebase.flutter.dev/docs/overview
こちらDetails are provided here

Below is an example of a CurrentUser decision

FirebaseAuth.instance
  .authStateChanges()
  .listen(User user){
    if(user==null){
      print('User is currently signed out!');
    } else{
      print('User is signed in!');
    }
  });

As long as you don't log out, even if you open the app after you close it, it won't transition to the login page

Fi FirebseSDK automatically perpetuates login

2022-09-30 14:39

If you have any answers or tips

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