Posted by: Satya Pavan Kantamani

If we want a verification mechanism we can optionally opt-in for it so that we can eliminate the garbage or un-trusted users or hackers. I will be writing more on the verification processes in my upcoming posts. If you want more details of the Email verification process check Authenticate with Email on Android and for the mobile verification process check out Authenticate using a Phone Number. Firebase backend services will verify those and return a response.

After the user’s successful sign-in, we can access and control basic user profile information and data stored in other firebase products. We can also use other methods to update user details.

For sign-in, we can either use the pre-built FirebaseUI library which handles the multiplatform UI flow or we can manually set up Firebase authentication SDK into the project.

Let’s check how to set up the project in Firebase.

Add Firebase To Your Project

For adding firebase to your app, first, we need to create a project in the firebase console. Let’s see how to do that step-by-step

Step 1

1. Go to firebase console and then click Add Project and enter a project name.
2. To register your app with firebase. Click on the Android icon to launch the setup flow. Enter the application package name, other details and click on the Register app.

Step 2

Add the Firebase configuration file into the app.

1. Download the google-services.json file and place it in the app module directory

2. In root or project-level build.gradle file, add google services Gradle plugin, also make sure that Google’s Maven repository → google() is added.

3. In the app-level build.gradle file apply google services plugin

plugins {
 id ‘com.google.gms.google-services’
}

4. Now add the Firebase Auth dependency in the app-level build.gradle

implementation 'com.google.firebase:firebase-auth-ktx:21.0.1'

Step 3

To use an authentication provider, we need to enable it in the Firebase console. Go to the sign-in method page in the Authentication section and enable the identity provider that you want for the application.

Left Menu → Build → Authentication

Step 2

Create an Activity and inflate layout file created above. Now declare an instance of FirebaseAuth

private lateinit var auth: FirebaseAuth

In onCreate() method initialize FirebaseAuth instance.

// Initialize Firebase Auth
auth = FirebaseAuth.getInstance()

Step 3

On activity initialization, check if the user is currently signed in or not. Based on the result we can do our custom implementation. Here we are currently navigating to HomeAcrivity on successful login by showing a toast message.

Step 4

If the user is not registered or logged in then we need to show a page requesting him to enter the details.

Let’s check the signup process for a new user with an email id and password. Now let’s create a new user with an email id and password. For this, in the Activity, create a function createNewUser() which takes the email id and password provided by the user on the sign-up button click

Step 5

Now let’s check the sign-in flow for an existing user with an email id and password. If the user is already created, sign in with an email id and password. For this, we can create a signInUser() function which takes the email id and password provided by the user on the sign-in button click.

Step 6

If a user is signed in successfully, we can access data by fetching the currentUser method from the Firebase Auth instance. Let’s create a home activity, where we can show user information after successful login.

Step 7

As we are done with sign-up and login flows let’s move to the log-out part. To sign out a user, call signOut method on the Firebase Auth instance

fun signOutUser(){
    Firebase.auth.signOut()
}

Step 8

The HomeActivity with user info and logout functions

Bonus: Sign in with a custom token

To create a custom token, refer to this link. When users sign in to the app, send user credentials to the authentication server, which will check the credentials and send a custom token if they are valid. After we receive the custom token, pass it to firebase auth to sign in user.

The final MainActivity code with sign up and sign-in flow

Now let’s run the app and check the output