Firebase helps you develop superb applications, grow your user base, and earn more money. As I mentioned in Chapter 1, Keep it Real - Firebase Realtime Database, each feature works autonomously, and they work far better together.

Assorted applications and web services need to have some type of authentication framework while keeping in mind the end goal of recognizing users. Use cases include  controlling access to premium data and to preserve user information. Without some approach to distinguishing one user from another, it would be impossible for the application to know which information and settings have a place with which user.

Despite the inspiration for adding user authentication to an application, developers usually find that implementing authentication is substantially more intricate than it appears. Not exclusively should verification...

As we learned in Chapter 1, Keep it real – Firebase Realtime Database, we can make use of Android Studio to integrate Firebase, or we can follow the traditional way of integrating Firebase features through the console by adding configuration files and dependencies manually.

In this chapter, we will explore the complete features and potential of Firebase Authentication. We will later create a new Android project and add the Firebase SDK and authentication Gradle dependency. 

Add the following dependency to an already configured project. At the time of writing, Firebase authentication had a version 16.0.1. It may vary in your builds, but the components class names will remain same:

implementation 'com.google.firebase:firebase-auth:16.0.1'

Firebase Authentication can follow two methods of implementation, one...

Email ID is a unique user identity that helps in sending and routing emails and notifications to users. So far, we have learned what authentication is. In this section, we will explore it with the help of working code. We will use the FirebaseUI Auth API, in which we will extend the concepts to apprehend in social login, phone number verification, and so on.

The following steps illustrate what necessary actions are to be taken to integrate the Firebase Authentication:

1. Create a new project with Empty Activity as the preferred template. In this project, we will explore social site integration and other authentication services. It is recommended...

Firebase Authentication for email credentials is one of the most simple and powerful onboarding features. To be able to make use of this facility, we need to enable the Email provider in the Firebase console. Using the Android Studio Firebase window, we can set up Firebase Authentication. Alternatively, we can add the configuration google-play-services.json file and dependencies manually. In your application level Gradle file, add the following dependency:

compile 'com.google.firebase:firebase-auth:11.8.0'

We need to declare an instance of the FirebaseAuth class, using which we can later get an access to the Firebase AuthResult object:

private FirebaseAuth mAuth;

We need to initialize the FirebaseAuth reference in the onCreate method, as shown here: 

mAuth = FirebaseAuth.getInstance();

Popular social networking sites include Google+, Facebook, and Twitter, whereas GitHub is more for engineers and software developers. Firebase can work with popular Authentication providers and it also supports non-popular authentication providers. We will explore the popular authentication providers using FirebaseUI. All of these providers use email and password credentials to log in to their services to retrieve user-related information. This means we don't have to enter the sign-up form to account creation all the required information is retrieved from providers. FirebaseUI makes the whole process sweet and simple. Since we have the projects ready to work on Authentication, we will follow the necessary steps to complete them. 

As we have understood that popular social networking sites are Google Plus, Facebook, and Twitter, whereas GitHub is more of engineers' and software developers' place. Firebase can work with popular Authentication providers, and it can also support the non-popular authentication providers. We will explore popular authentication providers using the Firebase SDK. 

Google authentication will use the instance of the GoogleSigninOptions class and also it needs a googleApiClient object. Using a builder pattern, we will construct the following code snippet that will be passed to googleApiClient later:

GoogleSignInOptions signInOptions...

As we continue to explore the Firebase toolchain, Authentication turned out to be the biggest chapter. It is a practical chapter; we have seen how to work with different auth providers and we have experience in using the FirebaseUI library. We have explored how to create an account using an email address, phone number, Google, Facebook, and Twitter. We have learned to fetch the API key for different providers, and we also learned how to retrieve the SHA-1 fingerprint inside Android Studio. All the code snippets that we have seen in this chapter are Android community recommended code. We have extensively used the Firebase SDK and FirebaseUI to build most of the authentication use cases. Customizing the email address, we have also understood the Firebase console, managing users, and so on. Overall social networking and phone number login, anonymous login and linking...