26.7 Firebase Authentication in Flutter: User Management

Authentication is an essential part of any modern application. Firebase Authentication provides a complete authentication system that supports email and password authentication, phone authentication, Google, Facebook, Twitter, and GitHub authentication, and much more. With Firebase Authentication, you can quickly and easily add authentication functionality to your Flutter app.

Configuring Firebase Authentication

To start using Firebase Authentication, you need to first create a Firebase project and connect your Flutter app to that project. Once you've done that, you can add the Firebase Authentication dependency to your `pubspec.yaml` file:

dependencies:
  firebase_auth: ^0.18.1+1

After adding the dependency, you need to import the Firebase Authentication package in your code:

import 'package:firebase_auth/firebase_auth.dart';

Authentication by Email and Password

Email and password authentication is the most basic form of authentication. With Firebase Authentication, you can create a new user with an email address and password using the `createUserWithEmailAndPassword` method:

FirebaseAuth auth = FirebaseAuth.instance;
try {
  UserCredential userCredential = await auth.createUserWithEmailAndPassword(
    email: "example@example.com",
    password: "SuperSecretPassword!"
  );
} on FirebaseAuthException catch (e) {
  if (e.code == 'weak-password') {
    print('The password provided is too weak.');
  } else if (e.code == 'email-already-in-use') {
    print('The account already exists for that email.');
  }
} catch (e) {
  print(e);
}

Once you create a user, you can authenticate that user using the `signInWithEmailAndPassword` method:

try {
  UserCredential userCredential = await auth.signInWithEmailAndPassword(
    email: "example@example.com",
    password: "SuperSecretPassword!"
  );
} on FirebaseAuthException catch (e) {
  if (e.code == 'user-not-found') {
    print('No user found for that email.');
  } else if (e.code == 'wrong-password') {
    print('Wrong password provided for that user.');
  }
} catch (e) {
  print(e);
}

Managing Users

Firebase Authentication provides several ways to manage users. For example, you can get the currently authenticated user using the `currentUser` property:

User user = auth.currentUser;

You can also listen for changes to the currently authenticated user using the `authStateChanges` stream:

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

Also, you can logout the current user using the `signOut` method:

await auth.signOut();

Conclusion

With Firebase Authentication, you can easily add authentication functionality to your Flutter app. Whether it's email and password authentication, phone authentication, Google, Facebook, Twitter, or GitHub authentication, Firebase Authentication has you covered.

In addition, Firebase Authentication provides several ways to manage users. You can get the currently authenticated user, listen for changes to the currently authenticated user, and log out the current user. This makes user management a breeze.

In summary, Firebase Authentication is an excellent choice for adding authentication functionality to your Flutter app.