public void logout(Activity context) {
   try {
     facebook.logout(context);
   } catch (Exception e) {
     if (listener != null) {
       listener.onError(new SocializeException(e));
     } else {
       if (logger != null) {
         logger.error(e.getMessage(), e);
       } else {
         e.printStackTrace();
       }
     }
   }
 }