Firebase Authentication


useful blogs & videos :

IMP : https://notes88081.blogspot.com/2020/10/email-password-validation-regex-in.html

https://youtu.be/q-AFYCkIMU8


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Firebase Authentication with Email & Password

Install Dependencies : https://firebase.google.com/docs/auth/android/password-auth

// Import the BoM for the Firebase platform
implementation platform('com.google.firebase:firebase-bom:28.3.0')

// Declare 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'


Simple SignOut , SignIn & Create User 


Before we send the email and password to the firebase , we validate the format of email and password.

Using trim() to remove spaces before and after the strings.


package com.deepesh.emailpasswordvalidationapp;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.content.res.ColorStateList;
import android.graphics.Color;
import android.os.Bundle;
import android.util.Patterns;
import android.view.View;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.android.material.textfield.TextInputLayout;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;

public class MainActivity extends AppCompatActivity {

    TextInputLayout email_et, password_et;
    TextView textview1;
    ProgressBar progressBar1;
    FirebaseAuth firebaseAuth_ref;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        email_et = findViewById(R.id.email_textlayout);
        password_et = findViewById(R.id.password_textlayout);
        textview1 = findViewById(R.id.textView1);

        progressBar1 = findViewById(R.id.progressBar1);
        progressBar1.setVisibility(View.GONE);

        // GET INSTANCE OF FIREBASE AUTH.
        firebaseAuth_ref = FirebaseAuth.getInstance();

    }



    boolean validateEmail() {

        String email_data = email_et.getEditText().getText().toString().trim();
        if (email_data.isEmpty()) {
            // sets the error label to the given text & color
            email_et.setErrorTextColor(ColorStateList.valueOf(Color.GREEN));
            email_et.setError("Email is Empty !");
            return false;
        } else if (!Patterns.EMAIL_ADDRESS.matcher(email_data).matches()) {

            // Matches the given email with the built-in Email Regex.
            // YOU CAN BUILD YOUR OWN PATTERN CLASS TOO
            email_et.setErrorTextColor(ColorStateList.valueOf(Color.GREEN));
            email_et.setError("Invalid Email entered !");
            return false;

        } else {
            email_et.setError(null);
            return true;
        }

    }


    boolean validatePassword() {

        String pass_data = password_et.getEditText().getText().toString().trim();

        if (pass_data.isEmpty()) {
            password_et.setError("Password is empty !");
            password_et.setErrorTextColor(ColorStateList.valueOf(Color.GREEN));
            return false;

        } else if (pass_data.length() < 6) {
            password_et.setError("Password must be more than 6 characters");
            password_et.setErrorTextColor(ColorStateList.valueOf(Color.GREEN));
            return false;
        } else {
            password_et.setError(null);
            return true;
        }
    }


    // signin button OnClick method
    public void SignIn(View view) {

        if (!validatePassword() | !validateEmail()) {
            // Email or Password not valid.
            return;
        }

        String email = email_et.getEditText().getText().toString().trim();
        String password = password_et.getEditText().toString().trim();
        progressBar1.setVisibility(View.VISIBLE);

        firebaseAuth_ref.signInWithEmailAndPassword(email,password)
                .addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if (task.isSuccessful()){

                            progressBar1.setVisibility(View.GONE);

                            Toast.makeText(MainActivity.this, "LOGGED IN", Toast.LENGTH_SHORT).show();
                            updateUI();
                        }else{
                            progressBar1.setVisibility(View.GONE);
                            Toast.makeText(MainActivity.this, "LOGGING FAIL !", Toast.LENGTH_SHORT).show();
                        }
                    }
                });


    }

    private void updateUI() {
        FirebaseUser user = firebaseAuth_ref.getCurrentUser();
        if (user == null){
            textview1.setText("User is Null / Not Logged In");
        }else{
            textview1.setText(user.getEmail());
        }
    }

    // Register button OnClick method
    public void createUser(View view) {

        if (!validateEmail() | !validatePassword()){
            return;
        }

        // As Your create the user  , by default you get signout
        // from your current user & get sign in into the user your created.

        String email = email_et.getEditText().getText().toString().trim();
        String password = password_et.getEditText().toString().trim();
        progressBar1.setVisibility(View.VISIBLE);

        firebaseAuth_ref.createUserWithEmailAndPassword(email,password)
                .addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {

                        if (task.isSuccessful()){
                            progressBar1.setVisibility(View.GONE);
                            Toast.makeText(MainActivity.this, "USER CREATED !", Toast.LENGTH_SHORT).show();
                        }else{
                            progressBar1.setVisibility(View.GONE);
                            Toast.makeText(MainActivity.this, "USER CREATION FAILED !", Toast.LENGTH_SHORT).show();
                        }

                    }
                });

    }


    @Override
    protected void onStart() {
        super.onStart();
        // Check if user is signed in (non-null) and update UI accordingly.
        updateUI();

    }

    // Signout button onClick button
    public void SignOut(View view) {
        firebaseAuth_ref.signOut();
        updateUI();
    }
}






<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">


    <com.google.android.material.textfield.TextInputLayout
        android:id="@+id/email_textlayout"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        app:errorEnabled="true"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <com.google.android.material.textfield.TextInputEditText
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:hint="Enter Email"
            android:inputType="textEmailAddress" />
    </com.google.android.material.textfield.TextInputLayout>


    <com.google.android.material.textfield.TextInputLayout
        android:id="@+id/password_textlayout"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        app:counterEnabled="true"
        app:errorEnabled="true"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/email_textlayout"
        app:passwordToggleEnabled="true">

        <com.google.android.material.textfield.TextInputEditText
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:hint="Enter Password"
            android:inputType="textPassword" />
    </com.google.android.material.textfield.TextInputLayout>


    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="48dp"
        android:layout_marginBottom="48dp"
        android:onClick="SignIn"
        android:text="Sign in"
        app:layout_constraintBottom_toBottomOf="@+id/signoutbutton"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/progressBar1" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="48dp"
        android:layout_marginEnd="28dp"
        android:layout_marginBottom="48dp"
        android:onClick="createUser"
        android:text="Register"
        app:layout_constraintBottom_toBottomOf="@+id/signoutbutton"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/progressBar1" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="95dp"
        android:text="Ready to Code"
        android:textSize="25sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/password_textlayout" />

    <ProgressBar
        android:id="@+id/progressBar1"
        style="?android:attr/progressBarStyle"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginTop="57dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView1" />

    <Button
        android:id="@+id/signoutbutton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="26dp"
        android:text="SignOut"
        android:onClick="SignOut"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>


EXAMPLE 2 :


<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">


    <EditText
        android:id="@+id/email_editText"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="76dp"
        android:hint="Email Adress"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/password_editText"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="41dp"
        android:hint="Password"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/email_editText" />

    <Button
        android:id="@+id/register_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="47dp"
        android:onClick="CreateUser"
        android:text="register"
        app:layout_constraintBottom_toBottomOf="@+id/delete_button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="@+id/delete_button" />

    <Button
        android:id="@+id/delete_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="48dp"
        android:layout_marginBottom="51dp"
        android:onClick="DeleteUser"
        android:text="Delete"
        app:layout_constraintBottom_toTopOf="@+id/signOut_button"
        app:layout_constraintStart_toStartOf="parent" />

    <TextView
        android:id="@+id/display_textview"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="120dp"
        android:layout_marginBottom="118dp"
        android:gravity="center"
        android:text="Hello World !"
        android:textSize="20sp"
        app:layout_constraintBottom_toTopOf="@+id/register_button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/password_editText" />

    <Button
        android:id="@+id/signOut_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="45dp"
        android:layout_marginBottom="83dp"
        android:onClick="SignOutUser"
        android:text="signout"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

    <Button
        android:id="@+id/signIn_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="1dp"
        android:layout_marginTop="45dp"
        android:onClick="SignInUser"
        android:text="signIn"
        app:layout_constraintStart_toStartOf="@+id/register_button"
        app:layout_constraintTop_toBottomOf="@+id/register_button" />


</androidx.constraintlayout.widget.ConstraintLayout>


package com.deepesh.exampleapp4;

import static android.content.ContentValues.TAG;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;

public class MainActivity extends AppCompatActivity {

    TextView display_textview;
    EditText email_editText, password_editText;
    Button delete_button, register_button, signIn_button, signOut_button;
    FirebaseAuth firebaseAuth;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        display_textview = findViewById(R.id.display_textview);
        email_editText = findViewById(R.id.email_editText);
        password_editText = findViewById(R.id.password_editText);
        delete_button = findViewById(R.id.delete_button);
        register_button = findViewById(R.id.register_button);
        signIn_button = findViewById(R.id.signIn_button);
        signOut_button = findViewById(R.id.signOut_button);
        firebaseAuth = FirebaseAuth.getInstance();

        if (firebaseAuth.getCurrentUser() == null) {
            display_textview.setText("Login Please");
        } else {
            display_textview.setText("LoggedIn Account : " + firebaseAuth.
                    getCurrentUser().getEmail().toString());
        }

    }

    public void CreateUser(View view) {

        // Creating a new User

        String email = email_editText.getText().toString().trim();
        String password = password_editText.getText().toString().trim();

        firebaseAuth.createUserWithEmailAndPassword(email, password).
                addOnCompleteListener(new OnCompleteListener<AuthResult>() {
            @Override
            public void onComplete(@NonNull Task<AuthResult> task) {

                if (task.isSuccessful()) {
                    Log.d(TAG, "onComplete: USER ACCOUNT CREATED SUCESSFULLY");
                } else {
                    Log.d(TAG, "onComplete: USER ACCOUNT CREATION FAILED !");
                }

            }
        });

    }

    public void DeleteUser(View view) {

        if (firebaseAuth.getCurrentUser() == null) {
            Log.d(TAG, "DeleteUser: PLEASE LOGIN BEFORE DELETING ACCOUNT.");
        } else {
            firebaseAuth.getCurrentUser().delete().
                    addOnCompleteListener(new OnCompleteListener<Void>() {
                @Override
                public void onComplete(@NonNull Task<Void> task) {
                    if (task.isSuccessful()) {
                        Log.d(TAG, "onComplete: USER ACCOUNT DELETED SUCESSFULLY");
                    } else {
                        Log.d(TAG, "onComplete: USER ACCOUNT DELETION FAILED !");
                    }
                }
            });
        }

    }

    public void SignOutUser(View view) {

        if (firebaseAuth.getCurrentUser() == null) {
            Log.d(TAG, "PLEASE LOGIN BEFORE SIGNING OUT ACCOUNT.");
        } else {
            firebaseAuth.signOut();
            display_textview.setText("Login Please");
        }

    }

    public void SignInUser(View view) {

        String email = email_editText.getText().toString().trim();
        String password = password_editText.getText().toString().trim();

        firebaseAuth.signInWithEmailAndPassword(email, password).
                addOnCompleteListener(new OnCompleteListener<AuthResult>() {
            @Override
            public void onComplete(@NonNull Task<AuthResult> task) {

                if (task.isSuccessful()) {
                    Log.d(TAG, "onComplete: USER SIGNIN SUCESSFULLY");
                } else {
                    Log.d(TAG, "onComplete: USER SIGNIN FAILED !");
                }

            }
        });

    }

}






----------------------------------------------------------------------------------------------------------------------------


FireBaseAuthStateListener( ) : 


You this event listener to listen for any state changes.




------------------------------------------------------------------------------------------------------


useful video : https://youtu.be/zgIGnEd1wMs


Firebase Error Handling During SignIn/Out Events.





Most of the error handling is done inside the OnFailureListener( ). 

We have 3 most important Exceptions that we get during SignIn , SignOut & Registration.

1] FirebaseAuthInvalidCredentials - User's Password is wrong.

2] FirebaseAuthInvalidUserException - User's email account is not registered.

3] FirebaseAuthUserCollision - We get this exception during Registration , if the email address provided already is registered inside the system.



firebaseAuth_ref.signInWithEmailAndPassword(email,password)
        .addOnCompleteListener(new OnCompleteListener<AuthResult>() {
            @Override
            public void onComplete(@NonNull Task<AuthResult> task) {
                if (task.isSuccessful()){

                    progressBar1.setVisibility(View.GONE);

                    Toast.makeText(MainActivity.this, "LOGGED IN", Toast.LENGTH_SHORT).show();
                    updateUI();
                }else{
                    progressBar1.setVisibility(View.GONE);
                    Toast.makeText(MainActivity.this, "LOGGING FAIL !", Toast.LENGTH_SHORT).show();

                    // Check for Exceptions during SignIn.
                    // You can also use this on Sucess/Failure Listeners.
                    if (task.getException() instanceof
                            FirebaseAuthInvalidCredentialsException){
                        textview1.setText("Password is wrong !");
                    }else if (task.getException() instanceof
                            FirebaseAuthInvalidUserException){
                        textview1.setText("Email provided is not registered !");
                    }
                }
            }
        });




firebaseAuth_ref.createUserWithEmailAndPassword(email,password)
        .addOnCompleteListener(new OnCompleteListener<AuthResult>() {
            @Override
            public void onComplete(@NonNull Task<AuthResult> task) {

                if (task.isSuccessful()){
                    progressBar1.setVisibility(View.GONE);
                    Toast.makeText(MainActivity.this, "USER CREATED !", Toast.LENGTH_SHORT).show();
                }else{
                    progressBar1.setVisibility(View.GONE);
                    Toast.makeText(MainActivity.this, "USER CREATION FAILED !", Toast.LENGTH_SHORT).show();

                    // Check for exception.
                    if (task.getException() instanceof
                            FirebaseAuthUserCollisionException){
                        textview1.setText("Provided Email is already registered !");
                    }
                }

            }
        });




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