Send Push Notifications in Android Using Firebase Cloud Messaging

📖 Introduction

Push notifications play a vital role in user engagement. Whether it’s alerting users about a new message, reminding them of an event, or updating content, push notifications keep your users informed in real time.

Firebase Cloud Messaging (FCM) is Google’s service that provides reliable, scalable, and cross-platform push notifications. In this post, we’ll walk through setting up FCM in an Android app, implementing token handling, and displaying notifications — all with clean, maintainable Kotlin code.

🔥 What is Firebase Cloud Messaging (FCM)?

Firebase Cloud Messaging is a cross-platform messaging solution that allows developers to deliver messages and notifications to Android, iOS, and web apps. It supports:

Notification messages: Automatically handled by the OS if the app is in the background.
Data messages: Custom data payloads processed by the app.
Topic messages: Broadcast messages to multiple users.
Device messages: Targeted messages to specific device tokens.

Why FCM?

Free to use
Integrates easily with Firebase Authentication, Analytics
Robust delivery with battery optimization
Scalable to millions of users

Diagram showing Firebase Auth and Realtime Database flow with Kotlin code blocks and app UI flow

⚙️ Step-by-Step Integration

1️⃣ Create a Firebase Project

Go to Firebase Console
Click “Add Project”
Follow the wizard — no need to enable Google Analytics for this tutorial
Once created, navigate to Project Settings → Cloud Messaging tab to get your Server Key (used for sending messages programmatically)

2️⃣ Connect Your Android App to Firebase

Register your Android app with your package name
Download google-services.json
Add it to your project at /app/google-services.json

3️⃣ Add Firebase Dependencies

In your root build.gradle file:

classpath 'com.google.gms:google-services:4.4.0'

In your app-level build.gradle:

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

dependencies {
    implementation 'com.google.firebase:firebase-messaging:24.0.0'
}

Sync the project after adding these.

🔐 Registering for Push Notifications

Retrieve Device Token

Tokens are needed to uniquely identify each device:

FirebaseMessaging.getInstance().token
    .addOnCompleteListener { task ->
        if (task.isSuccessful) {
            val token = task.result
            Log.d("FCM Token", token)
            // You may want to send this token to your server
        }
    }

You can also handle token refresh by overriding onNewToken:

override fun onNewToken(token: String) {
    Log.d("NEW_TOKEN", token)
    // Update your server with the new token
}

📲 Receiving Messages

Create a service to handle incoming messages:

class MyFirebaseMessagingService : FirebaseMessagingService() {

    override fun onMessageReceived(remoteMessage: RemoteMessage) {
        remoteMessage.notification?.let {
            showNotification(it.title, it.body)
        }

        remoteMessage.data.isNotEmpty().let {
            val data = remoteMessage.data
            val customValue = data["key_name"]
            // Handle custom data here
        }
    }

    private fun showNotification(title: String?, message: String?) {
        val builder = NotificationCompat.Builder(this, "fcm_channel")
            .setSmallIcon(R.drawable.ic_notification)
            .setContentTitle(title)
            .setContentText(message)
            .setPriority(NotificationCompat.PRIORITY_HIGH)
            .setAutoCancel(true)

        val manager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
        manager.notify(100, builder.build())
    }
}

AndroidManifest.xml Configuration

<service
    android:name=".MyFirebaseMessagingService"
    android:exported="false">
    <intent-filter>
        <action android:name="com.google.firebase.MESSAGING_EVENT" />
    </intent-filter>
</service>

Notification Channel (Android 8+)

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    val channel = NotificationChannel(
        "fcm_channel",
        "FCM Notifications",
        NotificationManager.IMPORTANCE_HIGH
    )
    val manager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
    manager.createNotificationChannel(channel)
}

Infographic showing steps to integrate Firebase Authentication and Realtime Database in Android apps

💬 Sending Test Push from Firebase Console

Go to Firebase Console → Cloud Messaging
Click “Send your first message”
Enter title/message
Under “Target”, select your app
Click “Send Message”

Within seconds, your app will receive the push if it’s running on a device or emulator with Play Services enabled.

🧠 Real-World Use Cases

Messaging apps: Show new message alerts
News apps: Breaking news notifications
E-commerce: Cart reminders, delivery tracking
Reminder apps: Scheduled alerts and updates

🔒 Securing FCM

Never expose your Server Key in the client
Always send FCM messages from your backend or using Firebase Functions
Use device groups or topics for better targeting

✅ Best Practices

Minimize unnecessary push messages to reduce opt-outs
Use rich notifications with images and action buttons
Track open rates with Firebase Analytics
Monitor delivery using Firebase Cloud Messaging reports
Use FCM Topics for segmented targeting (e.g., news, updates)

Firebase Cloud Messaging Key Point in Android

🔑 Key Points – Push Notifications in Android with FCM

What is FCM?
Firebase Cloud Messaging (FCM) is a cross-platform messaging solution that lets you send messages and notifications to Android, iOS, and web apps.
FCM vs Legacy GCM
FCM is the modern alternative to the deprecated Google Cloud Messaging (GCM). It provides enhanced features like topic messaging, device groups, and analytics.
Firebase Console Integration
Projects must be linked via the Firebase Console with your Android app’s package name and google-services.json configured properly.
FCM SDK Setup in Android
Use Firebase BoM in build.gradle, initialize Firebase in Application class, and implement Firebase Messaging Service.
Device Token Generation
Each app installation gets a unique device token used for identifying message recipients.
Handling Notifications
Use FirebaseMessagingService to handle messages when the app is in the foreground. For background messages, FCM automatically handles display.
Sending Test Notifications
Use Firebase Console or server API (HTTP v1 or legacy API) to send push notifications for testing and production use.
Topic Messaging
Send targeted notifications by subscribing users to topics like “news”, “offers”, or “updates”.
Data vs Notification Payload
- Notification Payload: Automatically handled by system tray (in background).
- Data Payload: Custom payload your app handles explicitly.
Handling App Launch from Notification
Implement intent filters to handle deep links or navigate to specific screens when users tap the notification.
Security & Best Practices

Never expose server keys in the client.
Use App Check and Authentication for secure message delivery.

Analytics & Delivery Reports
Integrate Firebase Analytics to track notification opens, delivery rates, and user engagement.

🔗 Internal Links

❓ FAQ (Copy-Paste for WordPress FAQ Block)

Q1: What is Firebase Cloud Messaging (FCM)?
A: FCM is a service from Firebase that allows developers to send notifications and messages to Android, iOS, and web apps — completely free.

Q2: Do I need a server to send FCM messages?
A: For sending messages to multiple users or using custom payloads, yes. You can use your own backend or Firebase Functions.

Q3: Can FCM handle both notifications and custom data?
A: Yes. Notification payloads are shown by the system UI, while data payloads are handled by your app in the background.

Sending Push Notifications in Android using Firebase Cloud Messaging