package org.forestguardian.Helpers;

import android.util.Log;

import com.google.firebase.messaging.FirebaseMessagingService;
import com.google.firebase.messaging.RemoteMessage;

/**
 * Created by luisalonsomurillorojas on 25/7/17.
 */

public class NotificationsMessageManager extends FirebaseMessagingService {

    private static final String TAG = NotificationsMessageManager.class.getSimpleName();

    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        // ...

        // TODO(developer): Handle FCM messages here.
        // Not getting messages here? See why this may be: https://goo.gl/39bRNJ
        Log.d(TAG, "From: " + remoteMessage.getFrom());

        // Check if message contains a data payload.
        if (remoteMessage.getData().size() > 0) {
            Log.d(TAG, "Message data payload: " + remoteMessage.getData());
        }

        // Check if message contains a notification payload.
        if (remoteMessage.getNotification() != null) {
            Log.d(TAG, "Message Notification Body: " + remoteMessage.getNotification().getBody());
        }

        // Also if you intend on generating your own notifications as a result of a received FCM
        // message, here is where that should be initiated. See sendNotification method below.
    }

}

package org.forestguardian.Helpers;

import android.app.NotificationManager;
import android.support.v4.app.NotificationCompat;
import android.util.Log;

import com.google.firebase.messaging.FirebaseMessagingService;
import com.google.firebase.messaging.RemoteMessage;

import org.forestguardian.R;

/**
 * Created by luisalonsomurillorojas on 25/7/17.
 */

public class NotificationsMessageManager extends FirebaseMessagingService {

    private static final String TAG = NotificationsMessageManager.class.getSimpleName();

    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        // ...

        // TODO(developer): Handle FCM messages here.
        // Not getting messages here? See why this may be: https://goo.gl/39bRNJ
        Log.d(TAG, "From: " + remoteMessage.getFrom());

        // Check if message contains a data payload.
        if (remoteMessage.getData().size() > 0) {
            Log.d(TAG, "Message data payload: " + remoteMessage.getData());
        }

        // Check if message contains a notification payload.
        if (remoteMessage.getNotification() != null) {
            Log.d(TAG, "Message Notification Body: " + remoteMessage.getNotification().getBody());
            sendNotification(remoteMessage.getNotification().getTitle(), remoteMessage.getNotification().getBody());
        }
    }

    private void sendNotification(String title, String body) {
        NotificationCompat.Builder mBuilder =
                new NotificationCompat.Builder(this)
                        .setSmallIcon(R.mipmap.ic_launcher)
                        .setContentTitle(title)
                        .setContentText(body);
        // Sets an ID for the notification
        int mNotificationId = (int)System.currentTimeMillis();
        // Gets an instance of the NotificationManager service
        NotificationManager mNotifyMgr = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        // Builds the notification and issues it.
        mNotifyMgr.notify(mNotificationId, mBuilder.build());
    }

}

Add android notifications