onPostExecute is getting null result on Android 4.2.2 -

my code working on upper version of android. whenever trying run program on jelly bean 4.2.2 not working. minimum sdk version is: 14 , target sdk version is: 22

my code is:

private class authasync extends asynctask<string, integer, string> {      @override     protected void onpreexecute() {     }      @override     protected string doinbackground(string... params) {          httpget request = new httpget(params[0] + params[1]);         responsehandler<string> responsehandler = new    basicresponsehandler();         string responsetxt = null;         httpclient client = paywellservices.gettrustedhttpclient();         try {             responsetxt = client.execute(request, responsehandler);         } catch (clientprotocolexception ex) {             ex.printstacktrace();         } catch (ioexception ex) {             ex.printstacktrace();         }         return responsetxt;     }      @override     protected void onpostexecute(string result) {         super.onpostexecute(result);          try {             log.e("log","try");             log.e("result",result);             if (result != null && result.contains("@")) {                 string splitedarray[] = result.split("@@@");             }        } catch (arrayindexoutofboundsexception e) {             log.e("log","catch");             e.printstacktrace();        }     } } 

technically, the result return doinbackground passed onpostexecute.
result input parameter on onpostexecute() same string returned in doinbackground() responsetxt

at first glance, im thinking of block of code in particular :

try {     responsetxt = client.execute(request, responsehandler); } catch (clientprotocolexception ex) {     ex.printstacktrace(); } catch (ioexception ex) {     ex.printstacktrace(); } return responsetxt; 

as debug, try check value (or print console) of responsetxt before returning it.
clue result of paywell client returning null when invoking method in :

responsetxt = client.execute(request, responsehandler);