Introducing FastChat: A Kotlin-Based Chat App Powered by Firebase

🚀 Overview

FastChat is a real-time chatting app built using Kotlin and Firebase Cloud Platform. It allows users to sign up, log in, send messages, and customize their settings in a fast, secure, and user-friendly environment.

🔗 GitHub Repository: [Complete Source Code Available Here]

📸 Sample Screenshots:

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📌 Key Features of FastChat

✅ User Authentication (Signup & Login) with Firebase Authentication
✅ Real-time Messaging powered by Firebase Firestore
✅ User Profile Settings (Change Display Name & Profile Picture)
✅ Secure & Scalable using Firebase Cloud Functions and Firestore Rules
✅ Push Notifications for New Messages (Optional)
✅ Responsive UI with Material Design Components

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🛠️ Tech Stack

• Frontend: Kotlin (Jetpack Compose or XML UI)
• Backend: Firebase Firestore, Firebase Authentication, Firebase Cloud Messaging (FCM)
• State Management: ViewModel + LiveData
• Dependency Injection: Hilt
• UI Components: Material Design

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🛠️ Step 1: Setting Up the Android Project

1️⃣ Install Android Studio

Download and install Android Studio from developer.android.com.

2️⃣ Create a New Android Project

1. Open Android Studio → Create a new project
2. Choose Empty Activity
3. Select Kotlin as the programming language

3️⃣ Add Firebase SDK to Your Project

1. Go to Firebase Console
2. Create a new project → Add an Android app
3. Register your app using the package name
4. Download google-services.json and place it in app/
5. Add dependencies in build.gradle (Module: app):

dependencies {
    implementation 'com.google.firebase:firebase-auth-ktx'
    implementation 'com.google.firebase:firebase-firestore-ktx'
    implementation 'com.google.firebase:firebase-storage-ktx'
}

6. Sync the project

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🛠️ Step 2: Implementing Authentication (Signup & Login)

1️⃣ Create Authentication Service (AuthService.kt)

import com.google.firebase.auth.FirebaseAuth

class AuthService {
    private val auth: FirebaseAuth = FirebaseAuth.getInstance()

    fun signUp(email: String, password: String, onResult: (Boolean, String?) -> Unit) {
        auth.createUserWithEmailAndPassword(email, password)
            .addOnCompleteListener { task ->
                if (task.isSuccessful) {
                    onResult(true, null)
                } else {
                    onResult(false, task.exception?.message)
                }
            }
    }

    fun login(email: String, password: String, onResult: (Boolean, String?) -> Unit) {
        auth.signInWithEmailAndPassword(email, password)
            .addOnCompleteListener { task ->
                if (task.isSuccessful) {
                    onResult(true, null)
                } else {
                    onResult(false, task.exception?.message)
                }
            }
    }

    fun logout() {
        auth.signOut()
    }
}

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2️⃣ Create Login Screen (LoginActivity.kt)

class LoginActivity : AppCompatActivity() {
    private lateinit var authService: AuthService

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_login)

        authService = AuthService()

        val emailField = findViewById<EditText>(R.id.email)
        val passwordField = findViewById<EditText>(R.id.password)
        val loginButton = findViewById<Button>(R.id.loginButton)

        loginButton.setOnClickListener {
            val email = emailField.text.toString()
            val password = passwordField.text.toString()

            authService.login(email, password) { success, message ->
                if (success) {
                    startActivity(Intent(this, ChatActivity::class.java))
                    finish()
                } else {
                    Toast.makeText(this, "Login Failed: $message", Toast.LENGTH_SHORT).show()
                }
            }
        }
    }
}

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🛠️ Step 3: Building the Messaging System

1️⃣ Define Message Model (Message.kt)

data class Message(
    val senderId: String = "",
    val message: String = "",
    val timestamp: Long = System.currentTimeMillis()
)

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2️⃣ Create Firestore Database for Chats

1. Go to Firebase Console → Firestore Database
2. Click "Start Collection" → Name it "messages"

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3️⃣ Implement Chat Service (ChatService.kt)

import com.google.firebase.firestore.FirebaseFirestore

class ChatService {
    private val db = FirebaseFirestore.getInstance()

    fun sendMessage(senderId: String, message: String) {
        val chatMessage = Message(senderId, message)
        db.collection("messages").add(chatMessage)
    }

    fun getMessages(onMessagesReceived: (List<Message>) -> Unit) {
        db.collection("messages").orderBy("timestamp")
            .addSnapshotListener { snapshot, _ ->
                snapshot?.let {
                    val messages = it.toObjects(Message::class.java)
                    onMessagesReceived(messages)
                }
            }
    }
}

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4️⃣ Create Chat Screen (ChatActivity.kt)

class ChatActivity : AppCompatActivity() {
    private lateinit var chatService: ChatService
    private lateinit var messageList: RecyclerView
    private lateinit var messageInput: EditText

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_chat)

        chatService = ChatService()
        messageList = findViewById(R.id.recyclerView)
        messageInput = findViewById(R.id.messageInput)

        val sendButton = findViewById<Button>(R.id.sendButton)
        sendButton.setOnClickListener {
            val message = messageInput.text.toString()
            if (message.isNotEmpty()) {
                chatService.sendMessage("user123", message)
                messageInput.text.clear()
            }
        }

        chatService.getMessages { messages ->
            messageList.adapter = MessageAdapter(messages)
        }
    }
}

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🛠️ Step 4: Deploying FastChat on Firebase

1️⃣ Enable Firebase Firestore Rules for Security

Go to Firestore Rules and add:

rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
    match /messages/{messageId} {
      allow read, write: if request.auth != null;
    }
  }
}

2️⃣ Run the App on an Android Device or Emulator

./gradlew installDebug

3️⃣ Publish the App on Google Play Store

Follow the Google Play Console guide to publish your app.

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🚀 Conclusion

FastChat is a fully functional real-time chat app built with Kotlin and Firebase.

🔗 GitHub Repository: [Complete Source Code Available Here]