26.4. Firebase Authentication in Flutter: User Authentication with Social Networks

One of the most important aspects when creating an application is user authentication. In Flutter, there are several ways to do this, but one of the most popular and effective is through Firebase. Firebase is an application development platform that offers a number of tools and services, including a user authentication system. In this chapter, we will cover Firebase Authentication in Flutter, focusing on authenticating users with social networks.

To get started, you need to configure Firebase in your Flutter project. This involves creating a Firebase project, adding your app to that project, and getting the necessary settings to connect your app to Firebase. You will also need to add Firebase dependencies to your pubspec.yaml file. The specific dependencies you need depend on the Firebase features you intend to use. For authentication you will need firebase_core and firebase_auth.

Once Firebase is set up, you can start implementing authentication. The first step is to create a FirebaseAuth instance. This allows you to access the methods and properties needed for authentication.

FirebaseAuth auth = FirebaseAuth.instance;

With this instance, you can use the signInWithCredential method to authenticate a user. This method accepts an AuthCredential object, which represents a user's authentication credentials. You can obtain these credentials in several ways, depending on the authentication method you are using.

To authenticate a user with a social network, you will need to obtain the authentication credentials for that social network. This usually involves redirecting the user to the social network login page and asking them to authorize your app. Once the user has authorized your app, the social network will provide authentication credentials, which you can then use to authenticate the user with Firebase.

For example, to authenticate a user with Google, you can use the google_sign_in package. First, you need to create an instance of GoogleSignIn.

GoogleSignIn googleSignIn = GoogleSignIn();

Then, you can use the signIn method to start the login process. This method returns a GoogleSignInAccount object, which represents the user's Google account.

GoogleSignInAccount googleUser = await googleSignIn.signIn();

With this account, you can get a GoogleSignInAuthentication object, which contains the user's Google authentication credentials.

GoogleSignInAuthentication googleAuth = await googleUser.authentication;

Finally, you can use these credentials to create a GoogleAuthCredential object, which you can use to authenticate the user with Firebase.

GoogleAuthCredential credential = GoogleAuthProvider.credential(
  accessToken: googleAuth.accessToken,
  idToken: googleAuth.idToken,
);

UserCredential userCredential = await auth.signInWithCredential(credential);

User authentication with other social networks works in a similar way. The main difference is how you get authentication credentials. For example, to authenticate a user with Facebook, you can use the flutter_facebook_login package.

Once a user is authenticated, you can access the user's information through FirebaseAuth's currentUser property. This returns a User object, which contains information such as the user's UID, email, and display name.

In short, Firebase authentication in Flutter is a relatively straightforward process. With Firebase, you can authenticate users with a variety of methods, including social networks like Google and Facebook. This provides a convenient and secure login experience for your users, which can help increase user retention and engagement.