> ## Documentation Index
> Fetch the complete documentation index at: https://documentation.onesignal.com/llms.txt
> Use this file to discover all available pages before exploring further.

# v4 Android Mobile Service Extensions

> Implement the iOS and Android notification service extensions in your app.

<Warning>
  This guide is for the v4 Android SDK. We recommend upgrading to our latest v5 User Model SDKs. See [Mobile SDKs API Migration Guides](/docs/en/user-model-migration-guide) to upgrade the OneSignal SDK.
</Warning>

Add the below Notification Extension Code if you want to do one of the following:

* Receive data in the background with or without displaying a notification.
* Override specific notification settings depending on client side app logic such as custom accent color, vibration pattern, or other any other `NotificationCompat` options available. See [Android's documentation on the NotificationCompat options.](https://developer.android.com/reference/androidx/core/app/NotificationCompat)

<Info>
  🚧 Requires writing Native Android code & Upgraded SDK.

  Must be using OneSignal SDK Versions:

  * Android 4.0.0 - 4.9.9
  * React Native 4.0.0 - 4.9.9
  * Flutter 3.0.0 - 3.9.9
  * Cordova/Ionic 3.0.0 - 3.9.9
  * Unity 3.0.0 - 3.9.9
  * Xamarin 4.0.0 - 4.9.9
</Info>

## Step 1. Create a class for the Service Extension

Create a class that extends `OSRemoteNotificationReceivedHandler` and implement the `remoteNotificationReceived` method.

The method `remoteNotificationReceived` parameters are `context` of type `Context` and `notificationReceivedEvent` of type `OSNotificationReceivedEvent`.

```java theme={null}
package your.package.name
  
import android.content.Context;
import android.util.Log;
import org.json.JSONObject;

import com.onesignal.OSNotification;
import com.onesignal.OSMutableNotification;
import com.onesignal.OSNotificationReceivedEvent;
import com.onesignal.OneSignal.OSRemoteNotificationReceivedHandler;

@SuppressWarnings("unused")
public class NotificationServiceExtension implements OSRemoteNotificationReceivedHandler {

    @Override
    public void remoteNotificationReceived(Context context, OSNotificationReceivedEvent notificationReceivedEvent) {
        OSNotification notification = notificationReceivedEvent.getNotification();

        // Example of modifying the notification's accent color
        OSMutableNotification mutableNotification = notification.mutableCopy();
        mutableNotification.setExtender(builder -> {
            // Sets the accent color to Green on Android 5+ devices.
            // Accent color controls icon and action buttons on Android 5+. Accent color does not change app title on Android 10+
            builder.setColor(new BigInteger("FF00FF00", 16).intValue());
            // Sets the notification Title to Red
            Spannable spannableTitle = new SpannableString(notification.getTitle());
            spannableTitle.setSpan(new ForegroundColorSpan(Color.RED),0,notification.getTitle().length(),0);
            builder.setContentTitle(spannableTitle);
            // Sets the notification Body to Blue
            Spannable spannableBody = new SpannableString(notification.getBody());
            spannableBody.setSpan(new ForegroundColorSpan(Color.BLUE),0,notification.getBody().length(),0);
            builder.setContentText(spannableBody);
            //Force remove push from Notification Center after 30 seconds
            builder.setTimeoutAfter(30000);
            return builder;
        });
        JSONObject data = notification.getAdditionalData();
        Log.i("OneSignalExample", "Received Notification Data: " + data);

        // If complete isn't called within a time period of 25 seconds, OneSignal internal logic will show the original notification
        // To omit displaying a notification, pass `null` to complete()
        // This will also prevent the notification received (confirmed receipt) event and click events on the push notification if handled differently.
        notificationReceivedEvent.complete(mutableNotification);
    }
}
```

## Step 2.  Add the following to your `AndroidManifest.xml`.

Add OneSignal class name and your class value as `meta-data` within the `AndroidManifest.xml` file under the application tag. Ignore any "unused" warnings.

```xml theme={null}
<application ...> 
  <!-- name doesn't change, value = your class fully name spaced-->
  <meta-data android:name="com.onesignal.NotificationServiceExtension"
     android:value="com.onesignal.example.NotificationServiceExtension" />
</application>
```