Google Firebase Login Authentication Implementation In Android

Introduction

• Email and password-based authentication.
• FirebaseUI (beta version).

1. After creating an account, add Firebase to your Android project and download Google-services.json file.
   
   
2. After adding the project place, download Google-Services.json into your Android app module root directory. Path : app/, otherwise Application will not connect with Firebase.
   
3. In build.gradle file of the project, add dependency:
   classpath 'com.google.gms:google-services:3.0.0'.
   
4. In build.gradle file of the app, add dependency and add the plugin.
   compile "com.google.firebase:firebase-auth:9.0.2"
   apply plugin: 'com.google.gms.google-services'
   
5. Now, go to the Firebase console, select the Auth option from the left panel. Enable the Email/Password, a sign-in provider in Sign-In method.
   
6. Get Firebase auth instance:
   private FirebaseAuth auth = FirebaseAuth.getInstance();
7. For creating a new account as a new user, there is a method called:
   1. createUserWithEmailAndPassword(email, password)
   3. auth.createUserWithEmailAndPassword(email, password)
   4. .addOnCompleteListener(SignupActivity.this, new OnCompleteListener<AuthResult>() {
   5. @Override
   6. public void onComplete(@NonNull Task<AuthResult> task) {
   7. Log.d(TAG, "createUserWithEmail:onComplete:" + task.isSuccessful());
   8. progressBar.setVisibility(View.GONE);
   9. // If sign in fails, display a message to the user. If sign in succeeds
   10. // the auth state listener will be notified and logic to handle the
   11. // signed in user can be handled in the listener.
   12. if (!task.isSuccessful()) {
   13. Toast.makeText(SignupActivity.this, "Authentication failed." + task.getException(),
   14. Toast.LENGTH_SHORT).show();
   15. } else {
   16. startActivity(new Intent(SignupActivity.this, MainActivity.class));
   17. finish();
   18. }
   19. }
   20. });
   
8. For authenticating the user, there is a method called: signInWithEmailAndPassword(email, password).
   1. auth.signInWithEmailAndPassword(email, password)
   2. .addOnCompleteListener(LoginActivity.this, new OnCompleteListener<AuthResult>() {
   3. @Override
   4. public void onComplete(@NonNull Task<AuthResult> task) {
   5. progressBar.setVisibility(View.GONE);
   6. if (!task.isSuccessful()) {
   7. if (password.length() < 6)
   8. {
   9. inputPassword.setError("Enter minimum 6 characters for password.");
   10. }
   11. else
   12. {
   13. Toast.makeText(LoginActivity.this, "Check your email and password. Authentication failed.", Toast.LENGTH_LONG).show();
   14. }
   15. }
   16. else
   17. {
   18. Intent intent = new Intent(LoginActivity.this, MainActivity.class);
   19. startActivity(intent);
   20. finish();
   21. }
   22. }
   23. });
   
9. Set up an AuthStateListener, that responds to the changes in the user's sign-in state:
   1. private FirebaseAuth.AuthStateListener authListener
   2. = new FirebaseAuth.AuthStateListener() {
   3. @Override
   4. public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
   5. FirebaseUser user = firebaseAuth.getCurrentUser();
   6. //If user is not signed in getCurrentUser method returns null
   7. if (user != null) {
   8. // User is signed in
   9. }
   10. else {
   11. // User is signed out
   12. startActivity(new Intent(MainActivity.this, LoginActivity.class));
   13. finish();
   14. }
   16. }
   17. };
   Note- AuthStateListener is added at the start of the activity and removed at the top of the activity.
   1. @Override
   2. public void onStart() {
   3. super.onStart();
   4. auth.addAuthStateListener(authListener);
   5. }
   7. @Override
   8. public void onStop() {
   9. super.onStop();
   10. if (authListener != null) {
   11. auth.removeAuthStateListener(authListener);
   12. }
   13. }
   If the user is signed in, we can find the details of the current user:
   final FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
   for examples:
   • user.getEmail()
   • user.getToken()
   • user.getDisplayName()
   • user.getProviderId()
   After a successful login with Email id: [email protected],
   You can check the list of the users in Firebase console:
   
   
10. In Firebase login authentication, there is also a functionality to send the password recovery instructions to the registered Email id.
    For this, there is a method called:
    1. sendPasswordResetEmail(emailId)
    3. auth.sendPasswordResetEmail(emailId)
    4. .addOnCompleteListener(new OnCompleteListener<Void>() {
    5. @Override
    6. public void onComplete(@NonNull Task<Void> task) {
    7. if (task.isSuccessful()) {
    8. Toast.makeText(PasswordResetActivity.this, "Instructions have been sent to your registered email id", Toast.LENGTH_SHORT).show();
    9. } else {
    10. Toast.makeText(PasswordResetActivity.this, "Sorry! Try Again.", Toast.LENGTH_SHORT).show();
    11. }
    12. progressBar.setVisibility(View.GONE);
    13. }
    14. });
    
    Password reset instructions to the registered Email id:
    
    On clicking, reset the password link:
    
    
11. For sign-out, there is a method called,
    signOut()
    auth.signOut();