title: Android - Firebase login based on facebook and calling Facebook Graph Api Issue
body: <p>I'm using firebase login based on Facebook Credentials, and I'm unable to call Facebook SDK methods. </p>
  
  <p>The problem appears when returning user open the app, 
  I'm checking if a user is logged in with </p>
  
  <pre><code> FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
  </code></pre>
  
  <p>if the user is not null he is logged in and enter the app.</p>
  
  <p>Next thing I'm trying to call Facebook Graph Request using </p>
  
  <pre><code>  AccessToken token = AccessToken.getCurrentAccessToken();
  </code></pre>
  
  <p>but token return as null. </p>
  
  <p>What is missing? is there a function that needs to be called after Firebase login so the Facebook SDK will be initialized with the right access token?</p>