How to Implement Push Notifications Using Firebase Cloud Messaging in Android

Set Up Firebase Cloud Messaging

• Ensure you have added the necessary Firebase dependencies to your project by updating your app's `build.gradle` file. You should include the Firebase Cloud Messaging dependency:

  ```gradle
  implementation 'com.google.firebase:firebase-messaging:23.0.0'
  ```

  Register your app with Firebase and download the `google-services.json` file, placing it in your app's `app` directory if not done already.</li>
  

Configuring Firebase in Your App

• Initialize Firebase in your application by calling `FirebaseApp.initializeApp(this);` in your `onCreate()` method within your main `Application` class or the main activity:

```java
@Override
public void onCreate() {
super.onCreate();
FirebaseApp.initializeApp(this);
}
```

Create a Firebase Messaging Service

• Create a class that extends `FirebaseMessagingService`. This class handles the reception of messages.

```java
public class MyFirebaseMessagingService extends FirebaseMessagingService {

  @Override
  public void onMessageReceived(RemoteMessage remoteMessage) {
      // Handle FCM messages here.
      if (remoteMessage.getNotification() != null) {
          // Since the notification is available, handle it here.
          sendNotification(remoteMessage.getNotification().getBody());
      }
  }

  private void sendNotification(String messageBody) {
      // Create and display a notification containing the received FCM message.
      NotificationCompat.Builder notificationBuilder = 
          new NotificationCompat.Builder(this, "default")
          .setContentTitle("FCM Message")
          .setSmallIcon(R.drawable.ic\_notification)
          .setContentText(messageBody)
          .setAutoCancel(true)
          .setPriority(NotificationCompat.PRIORITY\_HIGH);

      NotificationManagerCompat notificationManager = 
          NotificationManagerCompat.from(this);
      notificationManager.notify(0, notificationBuilder.build());
  }

}
```

Add Permissions and Service Declaration to Manifest

• Ensure you include necessary permissions and the service declaration in your `AndroidManifest.xml`:

```xml


<application
android:name=".MyApplication"
...>







```

Obtain Firebase Registration Token

• Obtain the Firebase registration token when needed to identify your app on a device:
  

```java
FirebaseMessaging.getInstance().getToken()
.addOnCompleteListener(new OnCompleteListener() {
@Override
public void onComplete(@NonNull Task task) {
if (!task.isSuccessful()) {
Log.w("FCM", "Fetching FCM registration token failed", task.getException());
return;
}

          // Get new FCM registration token
          String token = task.getResult();
          Log.d("FCM", "FCM registration token: " + token);

          // If you want to send messages to this application instance
          // or manage this apps subscriptions on the server side, send the
          // FCM registration token to your app server.
      }
  });

```

Handling Notifications

• When a message is received in the `onMessageReceived()` callback, extract the necessary data and display a notification. The provided `sendNotification()` method demonstrates how a simple notification can be created using the data from the message.
• Customize the notification as necessary for your app's requirements, potentially including actions, larger icons, or expanded layouts.

Test Notifications

• To test the notifications, use Firebase Console or server-side integration to send a message. Ensure the message has either a notification payload URL, or data payload if you want to handle the messaging component directly in your app's logic.
• Use tools like Postman to simulate server push messages for testing purposes if you’re handling data messages rather than notifications directly.