Get Started with Firebase Authentication on Android (2024)

• Firebase
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Connect your app to Firebase

If you haven't already,add Firebase to your Android project.

Add Firebase Authentication to your app

1. In your module (app-level) Gradle file(usually <project>/<app-module>/build.gradle.kts or<project>/<app-module>/build.gradle),add the dependency for the Firebase Authentication library for Android. We recommend using theFirebase Android BoMto control library versioning.

   dependencies { // Import the BoM for the Firebase platform implementation(platform("com.google.firebase:firebase-bom:33.3.0")) // Add the dependency for the Firebase Authentication library // When using the BoM, you don't specify versions in Firebase library dependencies implementation("com.google.firebase:firebase-auth")}

   By using the Firebase Android BoM, your app will always use compatible versions of Firebase Android libraries.

   (Alternative) Add Firebase library dependencieswithoutusing the BoM

   If you choose not to use the Firebase BoM, you must specify each Firebase library version in its dependency line.

   Note that if you use multiple Firebase libraries in your app, we strongly recommend using the BoM to manage library versions, which ensures that all versions are compatible.

   dependencies { // Add the dependency for the Firebase Authentication library // When NOT using the BoM, you must specify versions in Firebase library dependencies implementation("com.google.firebase:firebase-auth:23.0.0")}

   Looking for a Kotlin-specific library module? Starting inOctober 2023(Firebase BoM 32.5.0), both Kotlin and Java developers candepend on the main library module (for details, see theFAQ about this initiative).

2. To use an authentication provider, you need to enable it in theFirebase console. Go to the Sign-in Method page in the Firebase Authenticationsection to enable Email/Password sign-in and any other identity providersyou want for your app.

(Optional) Prototype and test with Firebase Local Emulator Suite

Before talking about how your app authenticates users, let's introduce a set oftools you can use to prototype and test Authentication functionality:Firebase Local Emulator Suite. If you're deciding among authentication techniquesand providers, trying out different data models with public and private datausing Authentication and Firebase Security Rules, or prototyping sign-in UI designs, being able towork locally without deploying live services can be a great idea.

An Authentication emulator is part of the Local Emulator Suite, whichenables your app to interact with emulated database content and config, aswell as optionally your emulated project resources (functions, other databases,and security rules).

Using the Authentication emulator involves just a few steps:

1. Adding a line of code to your app's test config to connect to the emulator.
2. From the root of your local project directory, running firebase emulators:start.
3. Using the Local Emulator Suite UI for interactive prototyping, or theAuthentication emulator REST API for non-interactive testing.

A detailed guide is available at Connect your app to the Authentication emulator.For more information, see the Local Emulator Suite introduction.

Now let's continue with how to authenticate users.

Check current auth state

1. Declare an instance of FirebaseAuth.

   Kotlin+KTX

   private lateinit var auth: FirebaseAuth
   EmailPasswordActivity.kt

   Java

   private FirebaseAuth mAuth;
   EmailPasswordActivity.java

2. In the onCreate() method, initialize the FirebaseAuth instance.

   Kotlin+KTX

   // Initialize Firebase Authauth = Firebase.auth
   EmailPasswordActivity.kt

   Java

   // Initialize Firebase AuthmAuth = FirebaseAuth.getInstance();
   EmailPasswordActivity.java

3. When initializing your Activity, check to see if the user is currently signedin.

   Kotlin+KTX

   public override fun onStart() { super.onStart() // Check if user is signed in (non-null) and update UI accordingly. val currentUser = auth.currentUser if (currentUser != null) { reload() }}
   EmailPasswordActivity.kt

   Java

   @Overridepublic void onStart() { super.onStart(); // Check if user is signed in (non-null) and update UI accordingly. FirebaseUser currentUser = mAuth.getCurrentUser(); if(currentUser != null){ reload(); }}
   EmailPasswordActivity.java

Sign up new users

Create a new createAccount method that takes in an email address and password,validates them, and then creates a new user with thecreateUserWithEmailAndPasswordmethod.

auth.createUserWithEmailAndPassword(email, password) .addOnCompleteListener(this) { task -> if (task.isSuccessful) { // Sign in success, update UI with the signed-in user's information Log.d(TAG, "createUserWithEmail:success") val user = auth.currentUser updateUI(user) } else { // If sign in fails, display a message to the user. Log.w(TAG, "createUserWithEmail:failure", task.exception) Toast.makeText( baseContext, "Authentication failed.", Toast.LENGTH_SHORT, ).show() updateUI(null) } }
EmailPasswordActivity.kt

mAuth.createUserWithEmailAndPassword(email, password) .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() { @Override public void onComplete(@NonNull Task<AuthResult> task) { if (task.isSuccessful()) { // Sign in success, update UI with the signed-in user's information Log.d(TAG, "createUserWithEmail:success"); FirebaseUser user = mAuth.getCurrentUser(); updateUI(user); } else { // If sign in fails, display a message to the user. Log.w(TAG, "createUserWithEmail:failure", task.getException()); Toast.makeText(EmailPasswordActivity.this, "Authentication failed.", Toast.LENGTH_SHORT).show(); updateUI(null); } } });
EmailPasswordActivity.java

Add a form to register new users with their email and password and call this newmethod when it is submitted. You can see an example in ourquickstart sample.

Sign in existing users

Create a new signIn method which takes in an email address and password,validates them, and then signs a user in with thesignInWithEmailAndPassword method.

auth.signInWithEmailAndPassword(email, password) .addOnCompleteListener(this) { task -> if (task.isSuccessful) { // Sign in success, update UI with the signed-in user's information Log.d(TAG, "signInWithEmail:success") val user = auth.currentUser updateUI(user) } else { // If sign in fails, display a message to the user. Log.w(TAG, "signInWithEmail:failure", task.exception) Toast.makeText( baseContext, "Authentication failed.", Toast.LENGTH_SHORT, ).show() updateUI(null) } }
EmailPasswordActivity.kt

mAuth.signInWithEmailAndPassword(email, password) .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() { @Override public void onComplete(@NonNull Task<AuthResult> task) { if (task.isSuccessful()) { // Sign in success, update UI with the signed-in user's information Log.d(TAG, "signInWithEmail:success"); FirebaseUser user = mAuth.getCurrentUser(); updateUI(user); } else { // If sign in fails, display a message to the user. Log.w(TAG, "signInWithEmail:failure", task.getException()); Toast.makeText(EmailPasswordActivity.this, "Authentication failed.", Toast.LENGTH_SHORT).show(); updateUI(null); } } });
EmailPasswordActivity.java

Add a form to sign in users with their email and password and call this newmethod when it is submitted. You can see an example in ourquickstart sample.

Access user information

If a user has signed in successfully you can get their account data atany point with the getCurrentUser method.

val user = Firebase.auth.currentUseruser?.let { // Name, email address, and profile photo Url val name = it.displayName val email = it.email val photoUrl = it.photoUrl // Check if user's email is verified val emailVerified = it.isEmailVerified // The user's ID, unique to the Firebase project. Do NOT use this value to // authenticate with your backend server, if you have one. Use // FirebaseUser.getIdToken() instead. val uid = it.uid}
MainActivity.kt

FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();if (user != null) { // Name, email address, and profile photo Url String name = user.getDisplayName(); String email = user.getEmail(); Uri photoUrl = user.getPhotoUrl(); // Check if user's email is verified boolean emailVerified = user.isEmailVerified(); // The user's ID, unique to the Firebase project. Do NOT use this value to // authenticate with your backend server, if you have one. Use // FirebaseUser.getIdToken() instead. String uid = user.getUid();}
MainActivity.java

Next Steps

Explore the guides on adding other identity and authentication services:

• Google Sign-in
• Facebook Login
• Anonymous Authentication