android - How to stop an activity from starting while checking if a user is logged in? -

i trying achieve following when user starts app:

1- if user not logged in show login screen. 2- if user created account , there valid token show start screen.

to end have implemented custom authenticator based on tutorial found here http://www.udinic.com/.

the code works, issue shows current activity ui briefly switches add account ui provided accountauthenticator. how can fixed this?

this code:

   @override public void onstart(){     super.onstart();     gettokenforaccountcreateifneeded(accountgeneral.account_type,    accountgeneral.authtoken_type_full_access);   }  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.main);     maccountmanager = accountmanager.get(this); }     /**  * auth token account.  * if not exist - add , return auth token.  * if 1 exist - return auth token.  * if more 1 exists - show picker , return select account's auth token.  * @param accounttype  * @param authtokentype  */ private void gettokenforaccountcreateifneeded(string accounttype, string authtokentype) {     final accountmanagerfuture<bundle> future = maccountmanager.getauthtokenbyfeatures(accounttype, authtokentype, null, this, null, null,             new accountmanagercallback<bundle>() {                 @override                 public void run(accountmanagerfuture<bundle> future) {                     bundle bnd = null;                     try {                         bnd = future.getresult();                         final string authtoken = bnd.getstring(accountmanager.key_authtoken);                         showmessage(((authtoken != null) ? "success!\ntoken: " + authtoken : "fail"));                       } catch (exception e) {                         e.printstacktrace();                         showmessage(e.getmessage());                     }                 }             }     , null); } 

force users login @ start of app. have implemented custom authenticator based on tutorial found here http://www.udinic.com/.

since authentication method asynchronous, can't prevent ui showing. implement router/splashscreen activity checks authentication status , starts either login activity or actual activity user sees if he's logged in. make sure set router activity nohistory in manifest.

if want keep in single activity, should have full-screen loading indicator in layout lays on top of ui , fades out once have figured out layout show.