Android Firebase Cloud Messaging Skeleton

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.example.example">
    <!-- ... -->
    <application
        <!-- ... --> >
  
        <!-- ... -->

        <!-- Firebase start -->
        <service
            android:name=".MyFirebaseMessagingService"
            android:exported="false">
            <intent-filter>
                <action android:name="com.google.firebase.MESSAGING_EVENT" />
            </intent-filter>
        </service>
        <!-- If you want to get data when app is not running -->
        <receiver
            android:name=".FirebaseDataReceiver"
            android:exported="true"
            android:permission="com.google.android.c2dm.permission.SEND">
            <intent-filter>
                <action android:name="com.google.android.c2dm.intent.RECEIVE" />
            </intent-filter>
        </receiver>
        <meta-data
            android:name="com.google.firebase.messaging.default_notification_channel_id"
            android:value="123" />
        <meta-data
            android:name="firebase_messaging_auto_init_enabled"
            android:value="false" />
        <meta-data
            android:name="firebase_analytics_collection_enabled"
            android:value="false" />
        <!-- Set custom default icon. This is used when no icon is set for incoming notification messages.
         See README(https://goo.gl/l4GJaQ) for more. -->
        <meta-data
            android:name="com.google.firebase.messaging.default_notification_icon"
            android:resource="@drawable/ic_arrow_left" />
        <!-- Set color used with incoming notification messages. This is used when no color is set for the incoming
             notification message. See README(https://goo.gl/6BKBk7) for more. -->
        <meta-data
            android:name="com.google.firebase.messaging.default_notification_color"
            android:resource="@color/colorAccent" />
        <!-- Firebase end -->
    </application>

</manifest>

FcmHelper.java

/** Add the following code where you want to initialize fcm.
FirebaseMessaging.getInstance().setAutoInitEnabled(true);
FcmHelper.saveFCMToken();
**/

public class FcmHelper {
    public static void saveFCMToken() {
        FirebaseInstanceId.getInstance().getInstanceId().addOnCompleteListener(task -> {
            if (!task.isSuccessful()) {
                Log.d("DEBUG", "FCM getInstanceId failed", task.getException());
                return;
            }
            // Get new Instance ID token
            String token = Objects.requireNonNull(task.getResult()).getToken();
            // TODO: Start token saving and sending scenario
            Log.d("DEBUG", "FCM getInstanceId new token -> " + token);
        });
    }
}

FirebaseDataReceiver.java

public class FirebaseDataReceiver extends BroadcastReceiver {
    Context mContext;

    @Override
    public void onReceive(Context context, Intent it) {
        Log.w("DEBUG", "FirebaseDataReceiver onReceive");
        this.mContext = context;

        Bundle bundle = it.getExtras();
        if(bundle == null) {
            Log.w("DEBUG", "FirebaseDataReceiver bundle is null");
            return;
        }

        if(isAppOnForeground(context)) {
            Log.w("DEBUG", "FirebaseDataReceiver app is running");
            // Don't do anything because MyFirebaseMessagingService will receive the message.
            return;
        }

        // TODO: App in background. Do something.
        // No need to display a notification manually. Firebase will show a notification.
    }

    private boolean isAppOnForeground(Context context) {
        ActivityManager activityManager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
        List<ActivityManager.RunningAppProcessInfo> appProcesses = activityManager.getRunningAppProcesses();
        if (appProcesses == null) {
            return false;
        }
        final String packageName = context.getPackageName();
        for (ActivityManager.RunningAppProcessInfo appProcess : appProcesses) {
            if (appProcess.importance == ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND && appProcess.processName.equals(packageName)) {
                return true;
            }
        }
        return false;
    }
}

MyFirebaseMessagingService.java

public class MyFirebaseMessagingService extends FirebaseMessagingService {

    /**
     * Called if InstanceID token is updated. This may occur if the security of
     * the previous token had been compromised. Note that this is called when the InstanceID token
     * is initially generated so this is where you would retrieve the token.
     */
    @Override
    public void onNewToken(@NonNull String token) {
        Log.i("DEBUG", "MyFirebaseMessagingService onNewToken: " + token);
        // TODO: Start token saving and sending scenario
    }

    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        Log.i("DEBUG", "MyFirebaseMessagingService onMessageReceived: " + remoteMessage.toString());
        Log.i("DEBUG", "MyFirebaseMessagingService From: " + remoteMessage.getFrom());
        Log.i("DEBUG", "MyFirebaseMessagingService data payload: " + remoteMessage.getData());
        // TODO: App in foreground. Do something.
        // Map<String, String> data = remoteMessage.getData();
    }
}