how to know in flutter if signin with user completed in firebase

To determine if a user has completed signing in with Firebase in Flutter, you can use the Firebase Authentication package. Here are the steps to achieve this:

Import the necessary packages: Start by importing the Firebase Authentication package in your Flutter project. To do this, add the following line in your pubspec.yaml file under the dependencies section:

dependencies:
  firebase_auth: ^3.3.0

Then, run flutter pub get to fetch the package.

Initialize Firebase: Before using Firebase services, you need to initialize Firebase in your Flutter app. Follow the official Firebase setup guide for Flutter to complete this step. Make sure you have the google-services.json file in the correct location.
Authenticate the user: After initializing Firebase, you can authenticate the user using various methods such as email/password, Google sign-in, Facebook sign-in, etc. Choose the appropriate method based on your requirements. Here's an example using email/password authentication:

import 'package:firebase_auth/firebase_auth.dart';

Future<void> signInWithEmailAndPassword(String email, String password) async {
  try {
    UserCredential userCredential = await FirebaseAuth.instance.signInWithEmailAndPassword(
      email: email,
      password: password,
    );
    // User sign-in successful
  } catch (e) {
    // Handle sign-in errors
  }
}

Replace email and password with the user's credentials.

Check sign-in status: Once the sign-in process is completed, you can check if the user is signed in by accessing the currentUser property of the FirebaseAuth instance. If it returns null, then the user is not signed in. Here's an example:

import 'package:firebase_auth/firebase_auth.dart';

void checkSignInStatus() {
  if (FirebaseAuth.instance.currentUser == null) {
    // User is not signed in
  } else {
    // User is signed in
  }
}

You can call the checkSignInStatus() function whenever you need to determine if the user has completed signing in.

That's it! By following these steps, you can determine if a user has completed signing in with Firebase in your Flutter app. Remember to handle error scenarios appropriately and customize the authentication flow based on your specific requirements.