title: Access data from Firebase Service in main thread
body: <p>I am programming an app that receives some data from a FCM message, then updates the UI based on the data payload contained in the message. </p>
  
  <p>The service runs fine, and receives the data, but I cant figure out how to get it back to my main activity. </p>
  
  <p>The Firebase service is declared in my manifest as</p>
  
  <pre><code>&lt;service android:name=".MyFirebaseService"&gt;
     &lt;intent-filter&gt;
         &lt;action android:name="com.google.firebase.MESSAGING_EVENT" /&gt;
     &lt;/intent-filter&gt;
  &lt;/service&gt;
  </code></pre>
  
  <p>In my MyFirebaseService class I have overridden the onMessageReceived method, but how am I supposed to notify my main activity that a message was received?</p>
  
  <p>Is there a handler I can use with the Firebase service?</p>