Login and Register App with Firebase Authentication Android Studio

In this app, a Login and Register App is created using the Firebase Authentication method. 

Go to https://console.firebase.google.com >>>> 

Add Project >>> 

Connect the Project Android Studio as per the method shown in video. ☝☝☝☝

Enable the E-mail authentication. 

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First, we will create the "MainActivity.class". The code snippet is as follows:

package com.example.firebaselogin;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import com.google.firebase.auth.FirebaseAuth;

import com.google.firebase.auth.FirebaseUser;

import com.google.firebase.ktx.Firebase;

import javax.security.auth.login.LoginException;

public class MainActivity extends AppCompatActivity {

private FirebaseAuth mAuth;

private Button btnLogout;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

mAuth = FirebaseAuth.getInstance();

btnLogout = findViewById(R.id.btnlogout);

btnLogout.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

logout();

} }); }

@Override

public void onStart(){

super.onStart();

FirebaseUser currentUser = mAuth.getCurrentUser();

if(currentUser==null)

{ startActivity(new Intent(MainActivity.this, LoginActivity.class));

} }

public void logout() {

FirebaseAuth.getInstance().signOut();

startActivity(new Intent(MainActivity.this, LoginActivity.class));

}}

The code snippet for "MainActivity.xml" is as follows: 

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout 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"

    android:layout_margin="10dp">

    <TextView

        android:id="@+id/text_welcome"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Welcome to Home Page!"

        android:layout_centerInParent="true"

        android:textSize="20dp"

        android:layout_marginBottom="20dp"

        />

    <Button

        android:id="@+id/btnlogout"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_below="@+id/text_welcome"

        android:text="Log Out"/>

</RelativeLayout>

Then we will create "LoginActivity.class". The code snippet is as follows:

package com.example.firebaselogin;

import androidx.annotation.NonNull;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

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.firebase.auth.AuthResult;

import com.google.firebase.auth.FirebaseAuth;

public class LoginActivity extends AppCompatActivity {

    private FirebaseAuth mAuth;

    private EditText email, password;

    private Button btnLogin;

    private TextView textRegister;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_login);

        mAuth = FirebaseAuth.getInstance();

        email = findViewById(R.id.login_email);

        password = findViewById(R.id.login_password);

        btnLogin  = findViewById(R.id.login);

        textRegister = findViewById(R.id.text_register);

        

        btnLogin.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                login();

            }

        });

        textRegister.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                startActivity(new Intent(LoginActivity.this, RegisterActivity.class));

            }        });    }

    private void login()

    {

        String user = email.getText().toString().trim();

        String pass = password.getText().toString().trim();

        if(user.isEmpty())

        {            email.setError("Email can not be empty");        }

        if(pass.isEmpty())

        {            password.setError("Password can not be empty");        }

        else

        {

            mAuth.signInWithEmailAndPassword(user,pass).addOnCompleteListener(new OnCompleteListener<AuthResult>() {

                @Override

                public void onComplete(@NonNull Task<AuthResult> task)

                {

                    if(task.isSuccessful())

                    {

                        Toast.makeText(LoginActivity.this, "Login Successful", Toast.LENGTH_SHORT).show();

                        startActivity(new Intent(LoginActivity.this , MainActivity.class));

                    }

                    else

                    {

                        Toast.makeText(LoginActivity.this, "Login Failed"+task.getException().getMessage(), Toast.LENGTH_SHORT).show();

                    }

                }

            });        }    } }

The code snippet for "LoginActivity.xml" is as follows:

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout 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=".LoginActivity"

    android:layout_margin="10dp">

    <TextView

        android:id="@+id/text_login"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:text="Enter Login Credentials"

        android:textSize="20dp"

        android:layout_marginBottom="20dp"/>

    <EditText

        android:id="@+id/login_email"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:hint="email"

        android:layout_below="@+id/text_login"

        android:layout_marginBottom="20dp"

        />

    <EditText

        android:id="@+id/login_password"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:hint="password"

        android:layout_below="@+id/login_email"

        android:layout_marginBottom="20dp"

        />

    <Button

        android:id="@+id/login"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_below="@+id/login_password"

        android:text="Login"

        android:layout_marginBottom="20dp"/>

    <TextView

        android:id="@+id/text_register"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_below="@+id/login"

        android:text="New User Register"

        android:layout_marginBottom="20dp"

        android:textAlignment="center"/>

</RelativeLayout>

Then we will create "RegisterActivity.class". The code snippet is as follows:

package com.example.firebaselogin;

import androidx.annotation.NonNull;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

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.firebase.auth.AuthResult;

import com.google.firebase.auth.FirebaseAuth;

public class RegisterActivity extends AppCompatActivity {

    private FirebaseAuth mAuth;

    private EditText email, password;

    private Button btnRegister;

    private TextView textLogin;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_register);

        mAuth = FirebaseAuth.getInstance();

        email = findViewById(R.id.register_email);

        password = findViewById(R.id.register_password);

        btnRegister  = findViewById(R.id.register);

        textLogin = findViewById(R.id.text_login);

        btnRegister.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                Register();

            }

        });

        textLogin.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                startActivity(new Intent(RegisterActivity.this, LoginActivity.class));

            }

        });

    }

    private void Register()

    {

        String user = email.getText().toString().trim();

        String pass = password.getText().toString().trim();

        if(user.isEmpty())

        {

            email.setError("Email can not be empty");

        }

        if(pass.isEmpty())

        {

            password.setError("Password can not be empty");

        }

        else

        {

            mAuth.createUserWithEmailAndPassword(user, pass).addOnCompleteListener(new OnCompleteListener<AuthResult>() {

                @Override

                public void onComplete(@NonNull Task<AuthResult> task) {

                    if(task.isSuccessful())

                    {

                        Toast.makeText(RegisterActivity.this, "User registered successfully", Toast.LENGTH_SHORT).show();

                        startActivity(new Intent(RegisterActivity.this, MainActivity.class));

                    }

                    else

                    {

                        Toast.makeText(RegisterActivity.this, "Registration Failed"+task.getException().getMessage(), Toast.LENGTH_SHORT).show();

                    }

                }

            });

        }

    }

}

The code snippet for "RegisterActivity.xml" is as follows:

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout 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=".RegisterActivity"

    android:layout_margin="10dp">

    <TextView

        android:id="@+id/text_register"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:text="Register Here"

        android:textSize="20dp"

        android:layout_marginBottom="20dp"/>

    <EditText

        android:id="@+id/register_email"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:hint="email"

        android:layout_below="@+id/text_register"

        android:layout_marginBottom="20dp"

        />

    <EditText

        android:id="@+id/register_password"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:hint="password"

        android:layout_below="@+id/register_email"

        android:layout_marginBottom="20dp"

        />

    <Button

        android:id="@+id/register"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_below="@+id/register_password"

        android:text="Register"

        android:layout_marginBottom="20dp"/>

    <TextView

        android:id="@+id/text_login"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_below="@+id/register"

        android:text="Existing User Login"

        android:layout_marginBottom="20dp"

        android:textAlignment="center"/>

</RelativeLayout>

Run the program

That's all folks, enjoy-----------------------------👱👱👱👱