title: Custom AccountAuthenticator: auth token getting
body: <p>When I try to get the auth token from <code>AccountManager</code> I need to call </p>
  
  <pre><code>AccountManagerFuture&lt;Bundle&gt; getAuthToken(Account account, String authTokenType, Bundle options, Activity activity, AccountManagerCallback&lt;Bundle&gt; callback, Handler handler);
  </code></pre>
  
  <p>What's difference between <code>AccountManagerFuture&lt;Bundle&gt;</code> and <code>AccountManagerCallback&lt;Bundle&gt;</code>? I read docs but it doesn't clearly.</p>
  
  <p>P.S. Maybe, it's noobie question but I really cannot understand it from Google docs.</p>