Firebase Authentication User Login

Android Firebase Login Tutorial

In this tutorial, we will learn how to implement a login activity in an Android application using Firebase Authentication. Follow the steps below to create a simple login screen with email and password authentication.

Step 1: Setup Firebase in your Android Project

First, you need to set up Firebase in your Android project. Follow these steps:

1. Create a new project on Firebase Console.
2. Add your Android app to the Firebase project by providing the package name.
3. Download the google-services.json file and place it in the app directory of your project.
4. Add Firebase SDK dependencies in your build.gradle files.

Step 2: Update build.gradle files

Project-level build.gradle

buildscript {
    repositories {
        // Check that you have the following line (if not, add it)
        google()
        mavenCentral()
    }
    dependencies {
        // Add these dependencies
        classpath 'com.android.tools.build:gradle:7.0.2'
        classpath 'com.google.gms:google-services:4.3.10'
    }
}

allprojects {
    repositories {
        google()
        mavenCentral()
    }
}

App-level build.gradle

apply plugin: 'com.android.application'
apply plugin: 'com.google.gms.google-services'

android {
    compileSdkVersion 30
    defaultConfig {
        applicationId "com.apdim3.firebaseeverythink"
        minSdkVersion 21
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation 'com.google.firebase:firebase-auth:21.0.3'
    implementation 'androidx.appcompat:appcompat:1.3.1'
    implementation 'com.google.android.material:material:1.4.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.0'
}

Step 3: Create the LoginActivity Layout

Create a new layout XML file named activity_login.xml in the res/layout directory with the following content:

<?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:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".LoginActivity">

    <EditText
        android:id="@+id/editTextEmail"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:hint="Email"
        android:inputType="textEmailAddress"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintMarginStart="32dp"
        app:layout_constraintMarginEnd="32dp"
        app:layout_constraintMarginTop="64dp"/>

    <EditText
        android:id="@+id/editTextPassword"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:hint="Password"
        android:inputType="textPassword"
        app:layout_constraintTop_toBottomOf="@id/editTextEmail"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintMarginStart="32dp"
        app:layout_constraintMarginEnd="32dp"
        app:layout_constraintMarginTop="16dp"/>

    <Button
        android:id="@+id/buttonLogin"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:text="Login"
        app:layout_constraintTop_toBottomOf="@id/editTextPassword"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintMarginStart="32dp"
        app:layout_constraintMarginEnd="32dp"
        app:layout_constraintMarginTop="32dp"/>

</androidx.constraintlayout.widget.ConstraintLayout>

Step 4: Create the LoginActivity Class

Create a new Java class named LoginActivity in the com.apdim3.firebaseeverythink package with the following content:

package com.apdim3.firebaseeverythink;

import android.os.Bundle;
import android.widget.Button;
import android.widget.EditText;

import androidx.appcompat.app.AppCompatActivity;

import com.google.firebase.auth.FirebaseAuth;

public class LoginActivity extends AppCompatActivity {

    private EditText edEmail, edPassword;
    private Button btnLogin;
    private FirebaseAuth auth;

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

        edEmail = findViewById(R.id.editTextEmail);
        edPassword = findViewById(R.id.editTextPassword);
        btnLogin = findViewById(R.id.buttonLogin);
        auth = FirebaseAuth.getInstance();

        btnLogin.setOnClickListener(v -> {
            String sEmail = edEmail.getText().toString();
            String sPass = edPassword.getText().toString();

            userLogin(sEmail, sPass);
        });
    }

    private void userLogin(String email, String password) {
        auth.signInWithEmailAndPassword(email, password)
            .addOnCompleteListener(this, task -> {
                if (task.isSuccessful()) {
                    // Sign in success, update UI with the signed-in user's information
                    // Redirect to another activity or update UI
                } else {
                    // If sign in fails, display a message to the user
                }
            });
    }
}

Conclusion

By following these steps, you have created a login screen in your Android application using Firebase Authentication. Now, users can sign in with their email and password. You can further enhance this example by adding form validation and better error handling.