How to Create a Login System in Android Studio ?

If you are building your first Android app, one of the most important features you’ll need is a login system.
A login system helps you identify users, secure data, and personalize the experience.

In this article, we’ll explain how to create a login system in Android Studio using Firebase Authentication — one of the easiest and most secure ways to handle user login in modern Android apps.

Android Studio Official Docs

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🔹 What You Will Learn

By the end of this tutorial, you’ll understand:

• How to connect your Android app with Firebase
• How to create registration and login screens
• How to authenticate users using email and password
• How to store and retrieve login data safely
• How to log out and secure user sessions

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🔹 Why Use Firebase Authentication?

Firebase, by Google, provides a powerful authentication system that supports:

• Email/Password login
• Google Sign-In
• Facebook or Twitter Login
• Anonymous authentication

Firebase handles all the backend logic for you — no need to build your own server or database for simple authentication.
This is why most new developers prefer Firebase Authentication for login systems.
(Firebase Auth Docs)

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🔹 Step 1: Create a New Android Project

1. Open Android Studio
2. Click File → New → New Project
3. Select Empty Activity and click Next
4. Give it a name, e.g. LoginApp
5. Choose language: Java or Kotlin
6. Set Minimum SDK: API 21 (Android 5.0 Lollipop)
7. Click Finish

Once it loads, you’ll see the default MainActivity.java and activity_main.xml.

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🔹 Step 2: Connect Your Project to Firebase

Firebase integration is simple inside Android Studio.

1. Go to Tools → Firebase (right sidebar will open)
2. Click Authentication → Email and Password Authentication
3. Click Connect to Firebase
4. Android Studio will open Firebase Console in browser — login with your Google account
5. Create a new Firebase project (same name as your app)
6. After connection, click Add Firebase Authentication to your app

Android Studio will automatically add these dependencies in your Gradle file:

implementation 'com.google.firebase:firebase-auth:22.0.0'

Make sure to Sync Project.

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🔹 Step 3: Enable Email/Password Authentication in Firebase

1. Go to your Firebase Console
2. Select your project → Authentication tab
3. Go to Sign-in method
4. Enable Email/Password
5. Click Save

Now Firebase will handle login and registration securely.

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🔹 Step 4: Create Login and Register Screens

Let’s design two XML layouts:

• activity_register.xml
• activity_login.xml

activity_register.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:padding="24dp"
    android:gravity="center"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <EditText
        android:id="@+id/email"
        android:hint="Enter Email"
        android:inputType="textEmailAddress"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <EditText
        android:id="@+id/password"
        android:hint="Enter Password"
        android:inputType="textPassword"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/registerBtn"
        android:text="Register"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

activity_login.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:padding="24dp"
    android:gravity="center"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <EditText
        android:id="@+id/loginEmail"
        android:hint="Email"
        android:inputType="textEmailAddress"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <EditText
        android:id="@+id/loginPassword"
        android:hint="Password"
        android:inputType="textPassword"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/loginBtn"
        android:text="Login"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

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🔹 Step 5: Register New Users

Create a new Java file RegisterActivity.java:

public class RegisterActivity extends AppCompatActivity {

    EditText email, password;
    Button registerBtn;
    FirebaseAuth auth;

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

        email = findViewById(R.id.email);
        password = findViewById(R.id.password);
        registerBtn = findViewById(R.id.registerBtn);

        auth = FirebaseAuth.getInstance();

        registerBtn.setOnClickListener(v -> {
            String userEmail = email.getText().toString();
            String userPass = password.getText().toString();

            if (userEmail.isEmpty() || userPass.isEmpty()) {
                Toast.makeText(this, "Please fill all fields", Toast.LENGTH_SHORT).show();
                return;
            }

            auth.createUserWithEmailAndPassword(userEmail, userPass)
                .addOnCompleteListener(task -> {
                    if (task.isSuccessful()) {
                        Toast.makeText(this, "Registered Successfully", Toast.LENGTH_SHORT).show();
                        finish(); // close register screen
                    } else {
                        Toast.makeText(this, "Error: " + task.getException().getMessage(), Toast.LENGTH_SHORT).show();
                    }
                });
        });
    }
}

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🔹 Step 6: Login Existing Users

Now create LoginActivity.java:

public class LoginActivity extends AppCompatActivity {

    EditText loginEmail, loginPassword;
    Button loginBtn;
    FirebaseAuth auth;

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

        loginEmail = findViewById(R.id.loginEmail);
        loginPassword = findViewById(R.id.loginPassword);
        loginBtn = findViewById(R.id.loginBtn);

        auth = FirebaseAuth.getInstance();

        loginBtn.setOnClickListener(v -> {
            String email = loginEmail.getText().toString();
            String pass = loginPassword.getText().toString();

            if (email.isEmpty() || pass.isEmpty()) {
                Toast.makeText(this, "All fields required", Toast.LENGTH_SHORT).show();
                return;
            }

            auth.signInWithEmailAndPassword(email, pass)
                .addOnCompleteListener(task -> {
                    if (task.isSuccessful()) {
                        Toast.makeText(this, "Login Successful", Toast.LENGTH_SHORT).show();
                        startActivity(new Intent(this, MainActivity.class));
                        finish();
                    } else {
                        Toast.makeText(this, "Login Failed", Toast.LENGTH_SHORT).show();
                    }
                });
        });
    }
}

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🔹 Step 7: Add Logout Option

In your MainActivity.java, you can add a logout button:

Button logoutBtn;
FirebaseAuth auth;

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

    logoutBtn = findViewById(R.id.logoutBtn);
    auth = FirebaseAuth.getInstance();

    logoutBtn.setOnClickListener(v -> {
        auth.signOut();
        startActivity(new Intent(this, LoginActivity.class));
        finish();
    });
}

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🔹 Step 8: Test Your Login System

Now run the app on an emulator or device:

1. Click Register and create a new account
2. Go to the Firebase Console → Authentication → Users — your new account will appear
3. Try logging in using that email and password
4. Verify you can logout and re-login

If everything works, your login system is complete! 🎉

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🔹 Common Mistakes to Avoid

1. Don’t forget to enable the Email/Password sign-in method in Firebase.
2. Always validate user input (email, password length, etc).
3. Add internet permission in AndroidManifest.xml: <uses-permission android:name="android.permission.INTERNET" />
4. Avoid storing passwords locally — Firebase already manages that securely.

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🔹 Conclusion

Creating a login system in Android Studio is not as hard as it looks — especially with Firebase Authentication.
It saves you from complex backend code, handles data safely, and scales automatically with your app.

To summarize:

• Use Firebase Authentication for quick and secure login
• Design clean, simple UI
• Always validate inputs
• Manage logout properly

Once done, you can expand it with Google Sign-In, OTP verification, or profile management.