title: retreive intent extra key value that was set in another class at MainActivity class
body: <p>I created an intent that is used for a notification in a class that extends FirebaseMessagingService.</p>
  <pre><code>  Intent intent = new Intent(getApplicationContext(), MainActivity.class);
          intent.putExtra(&quot;URL&quot;, link);
  </code></pre>
  <p>The user should click on the notification and go to the link. How to get this intent extra key and value from Mainactivity inside onResume() after the user clicks on the notification?</p>