Develop Reference

How to check if email was already used in firebase? [duplicate]

I want to check when a user attempts to signup with createUserWithEmailAndPassword() in Firebase user Authentication method, this user is already registered with my app.

To detect whether a user with that email address already exists, you can detect when the call to createUserWithEmailAndPassword () fails with auth/email-already-in-use. I see that #Srinivasan just posted an answer for this.
Alternatively, you can detect that an email address is already used by calling fetchSignInMethodsForEmail().
The usual flow for this is that you first ask the user to enter their email address, then call fetchSignInMethodsForEmail, and then move them to a screen that either asks for the rest of their registration details (if they're new), or show them the provider(s) with which they're signed up already.

When the user trying to create an user with same email address, the task response will be "Response: The email address is already in use by another account."
mFirebaseAuth.createUserWithEmailAndPassword(email,password)
.addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
#Override
public void onComplete(#NonNull Task<AuthResult> task) {
if(task.isSuccessful()){
//User registered successfully
}else{
Log.i("Response","Failed to create user:"+task.getException().getMessage());
}
}
});

First of all, you need to make sure you have that restriction enabled in Firebase console (Account and email address settings). Take a look at #Srinivasan's answer.
Then, do this in your java code:
firebaseAuthenticator.createUserWithEmailAndPassword(email, password)
.addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
#Override
public void onComplete(#NonNull Task<AuthResult> task) {
if (!task.isSuccessful()) {
if (task.getException() instanceof FirebaseAuthUserCollisionException) {
Toast.makeText(SignUpActivity.this, "User with this email already exist.", Toast.LENGTH_SHORT).show();
}
} else {
sendVerificationEmail();
startActivity(new Intent(SignUpActivity.this, DetailsCaptureActivity.class));
}
// ...
}
});
This is where the trick happens:
if (task.getException() instanceof FirebaseAuthUserCollisionException) {
Toast.makeText(SignUpActivity.this,
"User with this email already exist.", Toast.LENGTH_SHORT).show();
Several exceptions can be thrown when registering a user with email and password, but the one we are interested in is the FirebaseAuthUserCollisionException. As the name implies, this exception is thrown if the email already exists. If the exception thrown is an instance of this class, let the user know.

As a practice of #Frank's answer here is the code of using fetchProvidersForEmail()
private boolean checkAccountEmailExistInFirebase(String email) {
FirebaseAuth mAuth = FirebaseAuth.getInstance();
final boolean[] b = new boolean[1];
mAuth.fetchProvidersForEmail(email).addOnCompleteListener(new OnCompleteListener<ProviderQueryResult>() {
#Override
public void onComplete(#NonNull Task<ProviderQueryResult> task) {
b[0] = !task.getResult().getProviders().isEmpty();
}
});
return b[0];
}

I was looking into this kind of condition where we can detect if user exists or not and perform registration and login. fetchProvidersForEmail is best option right now. I have found this tutorial. Hope it helps you too!

See : Manage Users
UserRecord userRecord = FirebaseAuth.getInstance().getUserByEmail(email);
System.out.println("Successfully fetched user data: " + userRecord.getEmail());
This method returns a UserRecord object for the user corresponding to the email provided.
If the provided email does not belong to an existing user or the user cannot be fetched for any other reason, the Admin SDK throws an error. For a full list of error codes, including descriptions and resolution steps, see Admin Authentication API Errors.

private ProgressDialog progressDialog;
progressDialog.setMessage("Registering, please Wait...");
progressDialog.show();
mAuth.createUserWithEmailAndPassword(email, password)
.addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
#Override
public void onComplete(#NonNull Task<AuthResult> task) {
//checking if success
if (task.isSuccessful()) {
//Registration was successfull:
Toast.makeText(RegistrationActivity.this, "Successfully registered!", Toast.LENGTH_LONG).show();
} else {
//Registration failed:
//task.getException().getMessage() makes the magic
Toast.makeText(RegistrationActivity.this, "Registration failed! " + "\n" + task.getException().getMessage(), Toast.LENGTH_LONG).show();
}
progressDialog.dismiss();
}
});

Add below code to MainActivity.java file.When user attempt to register with the same email address a message "The email address is already used by another account" will pop up as a Toast
mAuth.createUserWithEmailAndPassword(email,password).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
#Override
public void onComplete(#NonNull Task<AuthResult> task) {
if(!task.isSuccessful()){
Toast.makeText(MainActivity.this, task.getException().getMessage(), Toast.LENGTH_SHORT).show();
}
if(task.isSuccessful()){
Toast.makeText(MainActivity.this, "Sign up successfull", Toast.LENGTH_SHORT).show();
}
}
});

You do not have to do anything because the backend of Firebase will do the job.
Unless you are referring to reauthenticating of the app.
Take a scenario for an example, w

Android Cloud Firestore: Query to find a users name

I've looked for multiple solutions here but couldn't find anything specific to my situation and therefore am posting a question here while I still continue looking for a solution. I'm fairly new to Firestore still and their guide/docs are still unclear.
My phone application has a system to get a user to enter in a name. This name is to be used to traverse the Firestore database and if the name exists as a field for one of the users, then the method must return a boolean of true.
This query is to be triggered by a "continue button" which is in my main activity as shown below:
//Authenticate user and proceed to next activity
continueBtn = (Button) findViewById(R.id.continue_btn);
continueBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//On click create a db reference and perform a query on it to find current user
//and authenticate it.
CollectionReference myRef = database.collection("users");
Query findNameQ = myRef.whereEqualTo("name", mUserName);
authenticateUser(findNameQ, mUserName);//I need to pass to this method a variable 'findNameQ' which can be used to validate the existence of a user.
//mUserName is the name it's looking for.
}
});
Once the query is run then it runs the authenticateUser method which basically validates the existence of the user and creates a new one if the user doesn't exist. Here's the method:
private void authenticateUser(Query findNameQ, String mUserName)
{
//Read from database and check if user exists
//if current users name matches to one in database then set userExists to true.
if (findNameQ != null)
{
userExists = true;
Toast.makeText(this, "User exists!", Toast.LENGTH_SHORT).show();
}
Toast.makeText(this, "User doesn't exist!", Toast.LENGTH_SHORT).show();
}
I'd like to use if (findNameQ != false) instead of null, how do I make it so my findNameQ variable is a boolean and not a query object?

In order to know if a user name exists in Firestore database, you need to use a get() call. Just creating a Query object will not provide you much. Beside that, if you are checking findNameQ != null it will always evaluate to true because findNameQ object is created and will never be null. So to solve this, please use the following lines of code:
productsRef.get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
#Override
public void onComplete(#NonNull Task<QuerySnapshot> task) {
if (task.isSuccessful()) {
for (QueryDocumentSnapshot document : task.getResult()) {
if (document.exists()) {
authenticateUser(findNameQ, mUserName);
}
}
}
}
});
Please also note, that using a addSnapshotListener will not help you because it will attach a listener to get data in real time but this is not what you need. You need to get the data only once.

You can use a boolean variable as
boolean nameFound = false;
Now, attach a snapshot listener to your query to check whether the name exists or not:
findNameQ.addSnapshotListener(new EventListener<QuerySnapshot>(){
#Override
public void onEvent(QuerySnapshot queryDocumentSnapshots, FirebaseFirestoreException e) {
for (DocumentSnapshot ds: queryDocumentSnapshots){
if (ds!=null && ds.exists()){
Toast.makeText(RegisterActivity.this, "Username Exists!", Toast.LENGTH_SHORT).show();
nameFound = true;
}
}
}
});
else the default value of nameFound that is false will be used. Now, use can use if else to call your authentication method based on the value of nameFound.

if statement checking for database information, works when it's not supposed to

I'm trying to make a error checking log in activity, where it will trigger an intent if it detects the following issues :
1) if user hasn't signed up (the email he used isn't authenticated with firebase) which is working out well for me
2) if user has signed up but didn't give me any information into the firebase database
My issue is that, for some reason the code i use to check for information in database, works for users even though they have information in the database attached to their UID.
meaning that the intent to tell them to give information will trigger when they already have given information.
if(task.isSuccessful()){
// Checks if user has submitted information in the Essential Information activity
//Takes the Unique ID(if it is present if not it will tell him to sign up or invalid email) asks the firebase database if he has given information to the database
reference.child("Users").child(UserUID).addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
// User exists
if (dataSnapshot.exists()) {
//Displays Toast telling user that their information is saved in the database
Toast.makeText(LogInActivity.this, "You have data in our database ", Toast.LENGTH_SHORT).show();
}
//User doesn't have information in the database
else {
// Displays Toast telling user he/she needs to sign in into the firebase database
// User goes to UserInformationActivity to give his/her information
Toast.makeText(LogInActivity.this, "You need to give Essential Information", Toast.LENGTH_SHORT).show();
// 3 second delay
final Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
// Goes to UserInformationActivity
Intent GoToUserInformation = new Intent(LogInActivity.this, UserInformationActivity.class);
LogInActivity.this.startActivity(GoToUserInformation);
}
}, 3000);
}
}
// if the checking got cancelled, likability of that happening is small
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}

Don't you want to check if the user is signed in?
Directly from firebase...
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
if (user != null) {
// User is signed in
// check a snapshot to see if there is information....if not, error out.
} else {
// No user is signed in
}

Promises in Java

The issue I am ultimately trying to solve, before I pose my question, is the synchronicity of querying my Firebase database and writing code based on the result. A simple example to illustrate:
Boolean userFound = false;
DatabaseReference userName = FirebaseDatabase.getInstance().getReference().child("Profiles").child("Name");
userName.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String name = dataSnapshot.getValue().toString();
userFound = true;
Toast.makeText(getBaseContext(), "Welcome back, " + name + ".", Toast.LENGTH_SHORT).show();
}
#Override
public void onCancelled(DatabaseError databaseError) {
//Never used this section
}
});
If (!userFound) {
Toast.makeText(getBaseContext(), "User not found.", Toast.LENGTH_SHORT).show();
}
In the example above, the listener looks for a name in the database. If the name is found it gives a welcome message and sets "userFound" to true. If a name is not found, "userFound" will remain as false and you can generate a user not found message.
The problem with this is that everything runs at the same instant and so you will always get the "User not found" message instantly, and then a few seconds later the listener might actually find the user and say "Welcome back".
I have been looking into how I can possible resolve this, and I have found Java Promises. Am I looking in the right direction? Here are two promise examples:
CompletableFuture.supplyAsync(this::failingMsg)
.exceptionally(ex -> new Result(Status.FAILED))
.thenAccept(this::notify);
This code looks great, and the article here is very detailed in its usage: http://www.deadcoderising.com/java8-writing-asynchronous-code-with-completablefuture/
Except for the fact that is will ONLY work in API 24 and above. Which means your app will not work on 90% of devices. So this is essentially worthless.
The other way of doing this is as follows:
try {
Promise { client.newCall(request).execute() }
.then { ... }
.thenAsync { ... }
.then { ... }
} catch (e: Exception) {
...
}
As explained here: https://medium.com/#sampsonjoliver/promises-in-android-and-java-d6b1c418ea6c
Except that when I try to use this code there is no such thing as Promise. It just says it cannot resolve the symbol. So this guy has written an article on something that doesn't even exist.
Am I looking at the right stuff here? The end game is to make my app wait for the result of any database lookup before continuing to process code. If I cannot do this, then the database becomes completely useless.
Thanks guys. Please help!

The solution with a problem using asynchronous APIs is pretty much always the same: move the code that needs access to the data into the method that is called when the data is available.
So in your case that means moving the check and toast into onDataChange:
DatabaseReference userName = FirebaseDatabase.getInstance().getReference().child("Profiles").child("Name");
userName.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Boolean userFound = false;
String name = dataSnapshot.getValue().toString();
userFound = true;
Toast.makeText(getBaseContext(), "Welcome back, " + name + ".", Toast.LENGTH_SHORT).show();
if (!userFound) {
Toast.makeText(getBaseContext(), "User not found.", Toast.LENGTH_SHORT).show();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException();
}
});
For more on this, see:
Setting Singleton property value in Firebase Listener
Doug's excellent blog post
Querying data from firebase
Wait Firebase async retrive data in android
Handle data returned by an Async task (Firebase)

How to catch a Firebase Auth specific exceptions

Using Firebase, how do I catch a specific exception and tell the user gracefully about it? E.g :
FirebaseAuthInvalidCredentialsException: The email address is badly
formatted.
I'm using the code below to signup the user using email and password, but I'm not that advanced in java.
mAuth.createUserWithEmailAndPassword(email, pwd)
.addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
#Override
public void onComplete(#NonNull Task<AuthResult> task) {
if (!task.isSuccessful()) {
//H.toast(c, task.getException().getMessage());
Log.e("Signup Error", "onCancelled", task.getException());
} else {
FirebaseUser user = mAuth.getCurrentUser();
String uid = user.getUid();
}
}
});

You can throw the Exception returned by task.getException inside a try block and catch each type of Exception that may be thrown by the method you are using.
Here is an example from the OnCompleteListener for the createUserWithEmailAndPassword method.
if(!task.isSuccessful()) {
try {
throw task.getException();
} catch(FirebaseAuthWeakPasswordException e) {
mTxtPassword.setError(getString(R.string.error_weak_password));
mTxtPassword.requestFocus();
} catch(FirebaseAuthInvalidCredentialsException e) {
mTxtEmail.setError(getString(R.string.error_invalid_email));
mTxtEmail.requestFocus();
} catch(FirebaseAuthUserCollisionException e) {
mTxtEmail.setError(getString(R.string.error_user_exists));
mTxtEmail.requestFocus();
} catch(Exception e) {
Log.e(TAG, e.getMessage());
}
}

In addition to #pdegand59 answer, I found some error code in Firebase library and test on Android (the returned error code). Hope this helps, Regards.
("ERROR_INVALID_CUSTOM_TOKEN", "The custom token format is incorrect. Please check the documentation."));
("ERROR_CUSTOM_TOKEN_MISMATCH", "The custom token corresponds to a different audience."));
("ERROR_INVALID_CREDENTIAL", "The supplied auth credential is malformed or has expired."));
("ERROR_INVALID_EMAIL", "The email address is badly formatted."));
("ERROR_WRONG_PASSWORD", "The password is invalid or the user does not have a password."));
("ERROR_USER_MISMATCH", "The supplied credentials do not correspond to the previously signed in user."));
("ERROR_REQUIRES_RECENT_LOGIN", "This operation is sensitive and requires recent authentication. Log in again before retrying this request."));
("ERROR_ACCOUNT_EXISTS_WITH_DIFFERENT_CREDENTIAL", "An account already exists with the same email address but different sign-in credentials. Sign in using a provider associated with this email address."));
("ERROR_EMAIL_ALREADY_IN_USE", "The email address is already in use by another account."));
("ERROR_CREDENTIAL_ALREADY_IN_USE", "This credential is already associated with a different user account."));
("ERROR_USER_DISABLED", "The user account has been disabled by an administrator."));
("ERROR_USER_TOKEN_EXPIRED", "The user\'s credential is no longer valid. The user must sign in again."));
("ERROR_USER_NOT_FOUND", "There is no user record corresponding to this identifier. The user may have been deleted."));
("ERROR_INVALID_USER_TOKEN", "The user\'s credential is no longer valid. The user must sign in again."));
("ERROR_OPERATION_NOT_ALLOWED", "This operation is not allowed. You must enable this service in the console."));
("ERROR_WEAK_PASSWORD", "The given password is invalid."));
("ERROR_MISSING_EMAIL", "An email address must be provided.";

There are a number of exceptions associated with firebase auth.
In addition to #kingspeech
You should use ((FirebaseAuthException)task.getException()).getErrorCode() to get the type of error and then handle it in switch like this :
private void loginUser(String email, String password) {
mAuth.signInWithEmailAndPassword(email, password).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
#Override
public void onComplete(#NonNull Task<AuthResult> task) {
if (task.isSuccessful()) {
startActivity(new Intent(MainActivity.this, Main2Activity.class));
} else {
String errorCode = ((FirebaseAuthException) task.getException()).getErrorCode();
switch (errorCode) {
case "ERROR_INVALID_CUSTOM_TOKEN":
Toast.makeText(MainActivity.this, "The custom token format is incorrect. Please check the documentation.", Toast.LENGTH_LONG).show();
break;
case "ERROR_CUSTOM_TOKEN_MISMATCH":
Toast.makeText(MainActivity.this, "The custom token corresponds to a different audience.", Toast.LENGTH_LONG).show();
break;
case "ERROR_INVALID_CREDENTIAL":
Toast.makeText(MainActivity.this, "The supplied auth credential is malformed or has expired.", Toast.LENGTH_LONG).show();
break;
case "ERROR_INVALID_EMAIL":
Toast.makeText(MainActivity.this, "The email address is badly formatted.", Toast.LENGTH_LONG).show();
etEmail.setError("The email address is badly formatted.");
etEmail.requestFocus();
break;
case "ERROR_WRONG_PASSWORD":
Toast.makeText(MainActivity.this, "The password is invalid or the user does not have a password.", Toast.LENGTH_LONG).show();
etPassword.setError("password is incorrect ");
etPassword.requestFocus();
etPassword.setText("");
break;
case "ERROR_USER_MISMATCH":
Toast.makeText(MainActivity.this, "The supplied credentials do not correspond to the previously signed in user.", Toast.LENGTH_LONG).show();
break;
case "ERROR_REQUIRES_RECENT_LOGIN":
Toast.makeText(MainActivity.this, "This operation is sensitive and requires recent authentication. Log in again before retrying this request.", Toast.LENGTH_LONG).show();
break;
case "ERROR_ACCOUNT_EXISTS_WITH_DIFFERENT_CREDENTIAL":
Toast.makeText(MainActivity.this, "An account already exists with the same email address but different sign-in credentials. Sign in using a provider associated with this email address.", Toast.LENGTH_LONG).show();
break;
case "ERROR_EMAIL_ALREADY_IN_USE":
Toast.makeText(MainActivity.this, "The email address is already in use by another account. ", Toast.LENGTH_LONG).show();
etEmail.setError("The email address is already in use by another account.");
etEmail.requestFocus();
break;
case "ERROR_CREDENTIAL_ALREADY_IN_USE":
Toast.makeText(MainActivity.this, "This credential is already associated with a different user account.", Toast.LENGTH_LONG).show();
break;
case "ERROR_USER_DISABLED":
Toast.makeText(MainActivity.this, "The user account has been disabled by an administrator.", Toast.LENGTH_LONG).show();
break;
case "ERROR_USER_TOKEN_EXPIRED":
Toast.makeText(MainActivity.this, "The user\\'s credential is no longer valid. The user must sign in again.", Toast.LENGTH_LONG).show();
break;
case "ERROR_USER_NOT_FOUND":
Toast.makeText(MainActivity.this, "There is no user record corresponding to this identifier. The user may have been deleted.", Toast.LENGTH_LONG).show();
break;
case "ERROR_INVALID_USER_TOKEN":
Toast.makeText(MainActivity.this, "The user\\'s credential is no longer valid. The user must sign in again.", Toast.LENGTH_LONG).show();
break;
case "ERROR_OPERATION_NOT_ALLOWED":
Toast.makeText(MainActivity.this, "This operation is not allowed. You must enable this service in the console.", Toast.LENGTH_LONG).show();
break;
case "ERROR_WEAK_PASSWORD":
Toast.makeText(MainActivity.this, "The given password is invalid.", Toast.LENGTH_LONG).show();
etPassword.setError("The password is invalid it must 6 characters at least");
etPassword.requestFocus();
break;
}
}
}
});
}

You should use ((FirebaseAuthException)task.getException()).getErrorCode() to get the type of error and fail gracefully if this is the error code for a bad formatted email.
Unfortunately, I couldn't find the list of error codes used by Firebase.
Trigger the exception once, note the error code and code accordingly.

Solution using Kotlin
fun signInWithEmail(email: String, passKey: String) {
FirebaseAuth.getInstance().signInWithEmailAndPassword(email, passKey).addOnSuccessListener {
it.user?.let {
authResultOperation.postValue(AuthResultOperation.OnSuccessSignIn)
}
}.addOnFailureListener {
val errorCode = (it.exception as FirebaseAuthException).errorCode
val errorMessage = authErrors[errorCode] ?: R.string.error_login_default_error
Toast.makeText(context, context.getString(errorMessage),Toast.LENGTH_LONG).show()
}
}
Explanation: Basically It's just a map that match firebase error codes with a custom string resource.
val authErrors = mapOf("ERROR_INVALID_CUSTOM_TOKEN" to R.string.error_login_custom_token,
"ERROR_CUSTOM_TOKEN_MISMATCH" to R.string.error_login_custom_token_mismatch,
"ERROR_INVALID_CREDENTIAL" to R.string.error_login_credential_malformed_or_expired,
"ERROR_INVALID_EMAIL" to R.string.error_login_invalid_email,
"ERROR_WRONG_PASSWORD" to R.string.error_login_wrong_password,
"ERROR_USER_MISMATCH" to R.string.error_login_user_mismatch,
"ERROR_REQUIRES_RECENT_LOGIN" to R.string.error_login_requires_recent_login,
"ERROR_ACCOUNT_EXISTS_WITH_DIFFERENT_CREDENTIAL" to R.string.error_login_accounts_exits_with_different_credential,
"ERROR_EMAIL_ALREADY_IN_USE" to R.string.error_login_email_already_in_use,
"ERROR_CREDENTIAL_ALREADY_IN_USE" to R.string.error_login_credential_already_in_use,
"ERROR_USER_DISABLED" to R.string.error_login_user_disabled,
"ERROR_USER_TOKEN_EXPIRED" to R.string.error_login_user_token_expired,
"ERROR_USER_NOT_FOUND" to R.string.error_login_user_not_found,
"ERROR_INVALID_USER_TOKEN" to R.string.error_login_invalid_user_token,
"ERROR_OPERATION_NOT_ALLOWED" to R.string.error_login_operation_not_allowed,
"ERROR_WEAK_PASSWORD" to R.string.error_login_password_is_weak)
String resources (Feel free to change it according to your requirements)
<resources>
<string name="error_login_custom_token">The custom token format is incorrect. Please check the documentation.</string>
<string name="error_login_custom_token_mismatch">The custom token corresponds to a different audience.</string>
<string name="error_login_credential_malformed_or_expired">The supplied auth credential is malformed or has expired.</string>
<string name="error_login_invalid_email">The email address is badly formatted.</string>
<string name="error_login_wrong_password">The password is invalid or the user does not have a password.</string>
<string name="error_login_user_mismatch">The supplied credentials do not correspond to the previously signed in user.</string>
<string name="error_login_requires_recent_login">This operation is sensitive and requires recent authentication. Log in again before retrying this request.</string>
<string name="error_login_accounts_exits_with_different_credential">An account already exists with the same email address but different sign-in credentials. Sign in using a provider associated with this email address.</string>
<string name="error_login_email_already_in_use">The email address is already in use by another account.</string>
<string name="error_login_credential_already_in_use">This credential is already associated with a different user account.</string>
<string name="error_login_user_disabled">The user account has been disabled by an administrator.</string>
<string name="error_login_user_not_found">There is no user record corresponding to this identifier. The user may have been deleted.</string>
<string name="error_login_operation_not_allowed">This operation is not allowed. You must enable this service in the console.</string>
<string name="error_login_password_is_weak">The given password is invalid.</string>
<string name="error_login_user_token_expired">The user\'s credential is no longer valid. The user must sign in again</string>
<string name="error_login_invalid_user_token">The user\'s credential is no longer valid. The user must sign in again.</string>
</resources>

If you simply want display a message to the user this works. Simple and Elegant:
if (!task.isSuccessful()) {
Log.w(TAG, "signInWithEmail:failed", task.getException());
Toast.makeText(LoginActivity.this, "User Authentication Failed: " + task.getException().getMessage(), Toast.LENGTH_SHORT).show();
}
It appears that the .getMessage() method converts the exception to a usable format for us already and all we have to do is display that somewhere to the user.
(This is my first comment, constructive criticism please)

You can use either steve-guidetti or pdegand59 method. I used steve-guidetti's method(Two exceptions are missing)
For all possible exception please find below ref.
It is well documented here.
https://firebase.google.com/docs/reference/js/firebase.auth.Auth
Search for "createUserWithEmailAndPassword" and find the
Error Codes
auth/email-already-in-use
Thrown if there already exists an account with the given email address.
auth/invalid-email
Thrown if the email address is not valid.
auth/operation-not-allowed
Thrown if email/password accounts are not enabled. Enable email/password accounts in the Firebase Console, under the Auth tab.
auth/weak-password
Thrown if the password is not strong enough.
For all five exceptions: Check here
https://firebase.google.com/docs/reference/android/com/google/firebase/auth/FirebaseAuthException
Here you can find 5 different types of AuthException. 4 Known Direct subclass and 1 indirect subclass
You can use either steve-guidetti or pdegand59 method.

If you are sending upstream messages from user to cloud, implement firebase callback functions onMessageSent and onSendError to check the status of upstream messages. In error cases, onSendError returns a SendException with an error code.
For example, if the client attempts to send more messages after the 20-message limit is reached, it returns SendException#ERROR_TOO_MANY_MESSAGES.

To catch a firebase Exception is easy, you should add .addOnFailureListener after you add .addOnCompleteListener like this:
private void login_user(String email, String password) {
mAuth.signInWithEmailAndPassword(email,password).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
#Override
public void onComplete(#NonNull Task<AuthResult> task) {
if(task.isSuccessful()){
Intent intent = new Intent(getApplicationContext(),MainActivity.class);
startActivity(intent);
finish();
}if(!task.isSuccessful()){
// To know The Excepton
//Toast.makeText(LoginActivity.this, ""+task.getException(), Toast.LENGTH_LONG).show();
}
}
}).addOnFailureListener(new OnFailureListener() {
#Override
public void onFailure(#NonNull Exception e) {
if( e instanceof FirebaseAuthInvalidUserException){
Toast.makeText(LoginActivity.this, "This User Not Found , Create A New Account", Toast.LENGTH_SHORT).show();
}
if( e instanceof FirebaseAuthInvalidCredentialsException){
Toast.makeText(LoginActivity.this, "The Password Is Invalid, Please Try Valid Password", Toast.LENGTH_SHORT).show();
}
if(e instanceof FirebaseNetworkException){
Toast.makeText(LoginActivity.this, "Please Check Your Connection", Toast.LENGTH_SHORT).show();
}
}
});

I tried another solutions but didn't like them.
What about this:
if (!task.isSuccessful()) {
Exception exc = task.getException();
if (exc.getMessage().contains("The email address is badly formatted.")) {
etUser.setError(getString(R.string.error_wrong_email));
etUser.requestFocus();
}
else
if (exc.getMessage().contains("There is no user record corresponding to this identifier. The user may have been deleted.")) {
etUser.setError(getString(R.string.error_user_not_exist));
etUser.requestFocus();
}
else
if (exc.getMessage().contains("The password is invalid or the user does not have a password")) {
etPass.setError(getString(R.string.error_wrong_password));
etPass.requestFocus();
}
Log.w(TAG, "signInWithEmail:failed", task.getException());
Toast.makeText(AuthActivity.this, R.string.auth_failed,
Toast.LENGTH_SHORT).show();
}

LOGIN_EXCEPTIONS
FirebaseAuthException - Generic exception related to Firebase Authentication. Check the error code and message for more details.
ERROR_USER_DISABLED if the user has been disabled (for example, in the Firebase console)
ERROR_USER_NOT_FOUND if the user has been deleted (for example, in the Firebase console, or in another instance of this app)
ERROR_USER_TOKEN_EXPIRED if the user's token has been revoked in the backend. This happens automatically if the user's credentials change in another device (for example, on a password change event).
ERROR_INVALID_USER_TOKEN if the user's token is malformed. This should not happen under normal circumstances.
mAuth.signInWithEmailAndPassword(login, pass)
.addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
#Override
public void onComplete(#NonNull Task<AuthResult> task) {
if(task.isSuccessful())
{
}else if (task.getException() instanceof FirebaseAuthInvalidUserException) {
}else if(((FirebaseAuthException) task.getException()).getErrorCode().equals("ERROR_USER_DISABLED"))
{
}else if(((FirebaseAuthException) task.getException()).getErrorCode().equals("ERROR_USER_NOT_FOUND "))
{
}else if(((FirebaseAuthException) task.getException()).getErrorCode().equals("ERROR_USER_TOKEN_EXPIRED "))
{
}else if(((FirebaseAuthException) task.getException()).getErrorCode().equals("ERROR_INVALID_USER_TOKEN "))
{
}
}
});
REGISTER_EXCEPTIONS
FirebaseAuthEmailException
Represents the exception which is a result of an attempt to send an email via Firebase Auth (e.g. a password reset email)
FirebaseAuthInvalidCredentialsException - Thrown when one or more of the credentials passed to a method fail to identify and/or authenticate the user subject of that operation. Inspect the error code and message to find out the specific cause.
FirebaseAuthWeakPasswordException - Thrown when using a weak password (less than 6 chars) to create a new account or to update an existing account's password. Use getReason() to get a message with the reason the validation failed that you can display to your users.

According to me the default message is informative enough. So I used it rather than any custom message and it worked pretty well for me.
if (!task.isSuccessful())
{
// there was an error
String yourString = task.getException().toString();
String target = "Exception:";
String error = yourString.substring(yourString.indexOf(target) + target.length() + 1, yourString.length());
Toast.makeText(LoginScreen.this, "Error: "+error, Toast.LENGTH_LONG).show();
}
p.s. this is my first answer on stack overflow. Do let me know if it was helpful.

try {
throw task.getException();
} catch(FirebaseAuthException e) {
switch (e.getErrorCode()){
case "ERROR_WEAK_PASSWORD":
Toast.makeText(this, "The given password is invalid.", Toast.LENGTH_SHORT).show();
break;
//and other
}
}
error codes: https://stackoverflow.com/a/38244409/2425851

In the past we used the getErrorCode() to get the type of error and fail gracefully. With the newer versions of the api, getErrorCode() is deprecated. We should use response.getError().getErrorCode() instead
com.firebase.ui.auth.IdpResponse
#Deprecated
public int getErrorCode()
Get the error code for a failed sign in
Deprecated use getError() instead
So for e.g.
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == RC_SIGN_IN) {
IdpResponse response = IdpResponse.fromResultIntent(data);
// Successfully signed in
if (resultCode == RESULT_OK) {
//dbHandler = DBMS.getInstance(this);
FirebaseAuth auth = FirebaseAuth.getInstance();
FirebaseUser user = auth.getCurrentUser();
FirebaseUserMetadata metadata = auth.getCurrentUser().getMetadata();
// initialize profile first
if (metadata.getCreationTimestamp() == metadata.getLastSignInTimestamp()) {
//start main activity after profile setup
startActivity(new Intent(this, MainActivity.class));
return;
} else {
// This is an existing user
// show them a welcome back screen.
startActivity(new Intent(this, MainActivity.class));
return;
}
} else {
// Sign in failed
// check response for error code
if (response == null) {
// User pressed back button
showSnackbar(R.string.sign_in_cancelled);
return;
}
if (response.getError().getErrorCode() == ErrorCodes.NO_NETWORK) {
showSnackbar(R.string.no_internet_connection);
return;
}
if (response.getError().getErrorCode() == ErrorCodes.UNKNOWN_ERROR) {
showSnackbar(R.string.unknown_error);
return;
}
}
showSnackbar(R.string.unknown_sign_in_response);
}
}

Try the following:
if (task.isSuccessful()) {
//Toast.makeText(getContext(),"Registration successful", Toast.LENGTH_SHORT).show();
try {
Toast.makeText(getContext(),"Registration successful", Toast.LENGTH_SHORT).show();
throw task.getException();
}
// if user enters wrong email.
catch (FirebaseAuthWeakPasswordException weakPassword) {
Log.d("Registration Error", "onComplete: weak_password");
// TODO: take your actions!
}
// if user enters wrong password.
catch (FirebaseAuthInvalidCredentialsException malformedEmail) {
Log.d("Registration Error", "onComplete: malformed_email");
// TODO: Take your action
}
catch (FirebaseAuthUserCollisionException existEmail) {
Log.d("Registration Error", "onComplete: exist_email");
// TODO: Take your action
}
catch (Exception e) {
Log.d("Registration Error", "onComplete: " + e.getMessage());
}
} else {
//Toast.makeText(getContext(), "ERROR, Please try again.", Toast.LENGTH_SHORT).show();
Toast.makeText(getContext(), task.getException().getMessage(), Toast.LENGTH_SHORT).show();
}

There are too many Firebase Authentication exceptions to handle, and I'm not sure if handling all of them is a good thing due to a large amount of code to add (as you can see from other answers).
I just got a FirebaseTooManyRequestsException after Task<AuthResult.isSuccessful() returned false:
firebaseAuth.signInWithEmailAndPassword(email, password)
.addOnCompleteListener {
if (it.isSuccessful) {
[...]
} else {
[FirebaseTooManyRequestsException and others that can be returned here]
}
}
com.google.firebase.FirebaseTooManyRequestsException: We have blocked all requests from this device due to unusual activity. Try again later. [ Access to this account has been temporarily disabled due to many failed login attempts. You can immediately restore it by resetting your password or you can try again later. ]
So, if you want to catch all of them or at least the ones that are more important to your logic, I hope that bringing another FirebaseAuth exception to this list helps you.

Here's a Kotlin parser that I use. it's adapted from FirebaseUI-Android
/**
* List of all possible results of [FirebaseAuthException.getErrorCode] and their meanings.
* TODO you can make description parameter private if you don't use it outside of this class
*/
enum class FirebaseAuthErrorParser(val description: String) {
ERROR_INVALID_CUSTOM_TOKEN("The custom token format is incorrect. Please check the documentation."),
ERROR_CUSTOM_TOKEN_MISMATCH("Invalid configuration. Ensure your app's SHA1 is correct in the Firebase console."),
ERROR_INVALID_CREDENTIAL("The supplied auth credential is malformed or has expired."),
ERROR_INVALID_EMAIL("The email address is badly formatted."),
ERROR_WRONG_PASSWORD("The password is invalid or the user does not have a password."),
ERROR_USER_MISMATCH("The supplied credentials do not correspond to the previously signed in user."),
ERROR_REQUIRES_RECENT_LOGIN("This operation is sensitive and requires recent authentication. Log in again before retrying this request."),
ERROR_ACCOUNT_EXISTS_WITH_DIFFERENT_CREDENTIAL("An account already exists with the same email address but different sign-in credentials. Sign in using a provider associated with this email address."),
ERROR_EMAIL_ALREADY_IN_USE("The email address is already in use by another account."),
ERROR_CREDENTIAL_ALREADY_IN_USE("This credential is already associated with a different user account."),
ERROR_USER_DISABLED("The user account has been disabled by an administrator."),
ERROR_USER_TOKEN_EXPIRED("The user's credential has expired. The user must sign in again."),
ERROR_USER_NOT_FOUND("There is no user record corresponding to this identifier. The user may have been deleted."),
ERROR_INVALID_USER_TOKEN("The user's credential is no longer valid. The user must sign in again."),
ERROR_OPERATION_NOT_ALLOWED("This operation is not allowed. Enable the sign-in method in the Authentication tab of the Firebase console"),
ERROR_TOO_MANY_REQUESTS("We have blocked all requests from this device due to unusual activity. Try again later."),
ERROR_WEAK_PASSWORD("The given password is too weak, please choose a stronger password."),
ERROR_EXPIRED_ACTION_CODE("The out of band code has expired."),
ERROR_INVALID_ACTION_CODE("The out of band code is invalid. This can happen if the code is malformed, expired, or has already been used."),
ERROR_INVALID_MESSAGE_PAYLOAD("The email template corresponding to this action contains invalid characters in its message. Please fix by going to the Auth email templates section in the Firebase Console."),
ERROR_INVALID_RECIPIENT_EMAIL("The email corresponding to this action failed to send as the provided recipient email address is invalid."),
ERROR_INVALID_SENDER("The email template corresponding to this action contains an invalid sender email or name. Please fix by going to the Auth email templates section in the Firebase Console."),
ERROR_MISSING_EMAIL("An email address must be provided."),
ERROR_MISSING_PASSWORD("A password must be provided."),
ERROR_MISSING_PHONE_NUMBER("To send verification codes, provide a phone number for the recipient."),
ERROR_INVALID_PHONE_NUMBER("The format of the phone number provided is incorrect. Please enter the phone number in a format that can be parsed into E.164 format. E.164 phone numbers are written in the format [+][country code][subscriber number including area code]."),
ERROR_MISSING_VERIFICATION_CODE("The phone auth credential was created with an empty sms verification code"),
ERROR_INVALID_VERIFICATION_CODE("The sms verification code used to create the phone auth credential is invalid. Please resend the verification code sms and be sure use the verification code provided by the user."),
ERROR_MISSING_VERIFICATION_ID("The phone auth credential was created with an empty verification ID"),
ERROR_INVALID_VERIFICATION_ID("The verification ID used to create the phone auth credential is invalid."),
ERROR_RETRY_PHONE_AUTH("An error occurred during authentication using the PhoneAuthCredential. Please retry authentication."),
ERROR_SESSION_EXPIRED("The sms code has expired. Please re-send the verification code to try again."),
ERROR_QUOTA_EXCEEDED("The sms quota for this project has been exceeded."),
ERROR_APP_NOT_AUTHORIZED("This app is not authorized to use Firebase Authentication. Please verify that the correct package name and SHA-1 are configured in the Firebase Console."),
ERROR_API_NOT_AVAILABLE("The API that you are calling is not available on devices without Google Play Services."),
ERROR_WEB_CONTEXT_CANCELED("The web operation was canceled by the user"),
ERROR_UNKNOWN("An unknown error occurred.");
companion object {
/**
* Get an [FirebaseAuthError.description] from an exception,
* returning [FirebaseAuthError.ERROR_UNKNOWN] as a default.
*/
fun fromException(ex: FirebaseAuthException): String {
return try {
valueOf(ex.errorCode).description
} catch (e: IllegalArgumentException) {
Log.e(TAG, e)
ERROR_UNKNOWN.description
}
}
}
}
This is how you use it:
val ErrorMsg = FirebaseAuthErrorParser.fromException(firebaseAuthEx)

you can use this:
mAuth.getCurrentUser().linkWithCredential(authCredential)
.addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
#Override
public void onComplete(#NonNull Task<AuthResult> task) {
if (task.isSuccessful()) {
Log.d(TAG, "linkWithCredential:success");
} else {
Log.w(TAG, "linkWithCredential:failure", task.getException());
Toast.makeText(getApplicationContext(), "Authentication failed. " + task.getException().toString, Toast.LENGTH_SHORT).show();
}
// ...
}
});