How to Use Firebase Cloud Messaging (FCM) with Android

To use Firebase Cloud Messaging (FCM) with Android, add Firebase to your project, include the firebase-messaging library, and create a service extending FirebaseMessagingService to handle messages. Then, register your app with Firebase and use the Firebase console or server to send notifications.

Syntax

Here is the basic syntax to set up FCM in an Android app:

• Add Firebase Messaging dependency in build.gradle.
• Create a class extending FirebaseMessagingService to receive messages.
• Override onMessageReceived to handle incoming messages.
• Use FirebaseMessaging.getInstance().getToken() to get the device token.

java

dependencies {
    implementation 'com.google.firebase:firebase-messaging:23.1.2'
}

public class MyFirebaseMessagingService extends FirebaseMessagingService {
    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        // Handle FCM messages here.
    }

    @Override
    public void onNewToken(String token) {
        // Send token to your server if needed.
    }
}

// To get the token
FirebaseMessaging.getInstance().getToken()
    .addOnCompleteListener(task -> {
        if (!task.isSuccessful()) {
            return;
        }
        String token = task.getResult();
        // Use or send token
    });

Example

This example shows a complete minimal setup for receiving FCM messages in an Android app. It includes the service class and how to get the token.

java

dependencies {
    implementation 'com.google.firebase:firebase-messaging:23.1.2'
}

public class MyFirebaseMessagingService extends FirebaseMessagingService {
    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        if (remoteMessage.getNotification() != null) {
            String title = remoteMessage.getNotification().getTitle();
            String body = remoteMessage.getNotification().getBody();
            // Show notification or handle message
            System.out.println("Notification Received: " + title + " - " + body);
        }
    }

    @Override
    public void onNewToken(String token) {
        System.out.println("New token: " + token);
        // Send token to your server if needed
    }
}

// In your main activity or initialization code
FirebaseMessaging.getInstance().getToken()
    .addOnCompleteListener(task -> {
        if (!task.isSuccessful()) {
            System.out.println("Fetching FCM registration token failed");
            return;
        }
        String token = task.getResult();
        System.out.println("FCM Token: " + token);
    });

Output

Notification Received: Sample Title - Sample message body
FCM Token: abc123xyz456token

Common Pitfalls

Common mistakes when using FCM with Android include:

• Not adding the google-services.json file to the app folder.
• Forgetting to add the Firebase Messaging dependency.
• Not declaring the FirebaseMessagingService in the AndroidManifest.xml.
• Not handling the token refresh properly.
• Trying to receive messages without internet permission.

Always check your Firebase project setup and app configuration.

xml

/* Wrong: Missing service declaration in AndroidManifest.xml */

<!-- No service tag for FirebaseMessagingService -->

/* Right: Add this inside <application> tag in AndroidManifest.xml */
<service
    android:name=".MyFirebaseMessagingService"
    android:exported="false">
    <intent-filter>
        <action android:name="com.google.firebase.MESSAGING_EVENT" />
    </intent-filter>
</service>

Quick Reference

Key steps to use FCM with Android:

• Add Firebase to your Android project via Firebase Console.
• Download and add google-services.json to your app folder.
• Add firebase-messaging dependency in build.gradle.
• Create a service extending FirebaseMessagingService to handle messages.
• Get the device token with FirebaseMessaging.getInstance().getToken().
• Send notifications from Firebase Console or your server using the token.

Key Takeaways

Add Firebase and firebase-messaging dependency to your Android project.

Create a FirebaseMessagingService subclass to handle incoming messages.

Always include google-services.json and declare your service in AndroidManifest.xml.

Use FirebaseMessaging.getInstance().getToken() to get the device token for sending messages.

Test notifications using Firebase Console before integrating server-side messaging.