code: public static Session openActiveSessionWithAccessToken(Context context, AccessToken accessToken,
              StatusCallback callback) {
          Session session = new Session(context, null, null, false);
  
          setActiveSession(session);
          session.open(accessToken, callback);
  
          return session;
      }
docs: Opens a session based on an existing Facebook access token, and also makes this session
  the currently active session. This method should be used
  only in instances where an application has previously obtained an access token and wishes
  to import it into the Session/TokenCachingStrategy-based session-management system. A primary
  example would be an application which previously did not use the Facebook SDK for Android
  and implemented its own session-management scheme, but wishes to implement an upgrade path
  for existing users so they do not need to log in again when upgrading to a version of
  the app that uses the SDK. In general, this method will be called only once, when the app
  detects that it has been upgraded -- after that, the usual Session lifecycle methods
  should be used to manage the session and its associated token.
  <p/>
  No validation is done that the token, token source, or permissions are actually valid.
  It is the caller's responsibility to ensure that these accurately reflect the state of
  the token that has been passed in, or calls to the Facebook API may fail.
  
  @param context     the Context to use for creation the session
  @param accessToken the access token obtained from Facebook
  @param callback    a callback that will be called when the session status changes; may be null
  @return The new Session or null if one could not be created