android - ListView works in emulator, but not in phone -

i tried make simple application take api internet, rearrange them , show list.

in emulator works. phone shows white screen. phone has android 2.3.7. when tried on tablet, app stopped working. tablet has android 4.1.

mainactivity

public class mainactivity extends listactivity implements onitemclicklistener{      private progressdialog pdialog;      private string url = "http://www.cscpro.org/secura/market/"; //food-29-5.json;     private string res;     private string ql;      jsonarray market;     final static string resources = "res";     final static string quality = "q";     private static final string tag_offer = "offer";     private static final string tag_price = "price";     private static final string tag_saller = "seller";     private static final string tag_saller_name = "name";      arraylist<hashmap<string, string>> listsaller;      public void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main);         listsaller = new arraylist<hashmap<string, string>>();         intent in = getintent();         res = in.getstringextra(resources);         ql = in.getstringextra(quality);         listview lv = getlistview();         lv.setonitemclicklistener(this);                      // calling async task json         new getcontacts().execute();     }      @override     public void onitemclick(adapterview<?> parent, view view,             int position, long id) {         string rate = ((textview) view.findviewbyid(r.id.rate)).gettext().tostring();         string name = ((textview) view.findviewbyid(r.id.name)).gettext().tostring();          // starting single contact activity         intent in = new intent(getapplicationcontext(),                 singlecontactactivity.class);         in.putextra(tag_price, rate);         in.putextra(tag_saller_name, name);         startactivity(in);     }      private class getcontacts extends asynctask<void, void, void> {          @override         protected void onpreexecute() {             super.onpreexecute();             // showing progress dialog             pdialog = new progressdialog(mainactivity.this);             pdialog.setmessage("please wait...");             pdialog.setcancelable(false);             pdialog.show();         }          @override         protected void doinbackground(void... arg0) {             // creating service handler class instance             servicehandler sh = new servicehandler();              // making request url , getting response             string myurl = url+res+"-29-"+ql+".json";             string jsonstr = sh.makeservicecall(myurl, servicehandler.get);              log.d("response: ", "> " + jsonstr);              if (jsonstr != null) {                 try {                     jsonobject jsonobj = new jsonobject(jsonstr);                      // getting json array node                     market = jsonobj.getjsonarray(tag_offer);                      // looping through contacts                     (int = 0; < market.length(); i++) {                         jsonobject c = market.getjsonobject(i);                          string rate = c.getstring(tag_price);                          // phone node json object                         jsonobject saller = c.getjsonobject(tag_saller);                         string name = saller.getstring(tag_saller_name);                          // tmp hashmap single contact                         hashmap<string, string> sallers = new hashmap<string, string>();                          // adding each child node hashmap key => value                         sallers.put(tag_price, rate);                         sallers.put(tag_saller_name, name);                          // adding contact contact list                         listsaller.add(sallers);                     }                 } catch (jsonexception e) {                     e.printstacktrace();                 }             } else {                 log.e("servicehandler", "couldn't data url");             }              return null;         }          @override         protected void onpostexecute(void result) {             super.onpostexecute(result);             // dismiss progress dialog             if (pdialog.isshowing())                 pdialog.dismiss();             /**              * updating parsed json data listview              * */             listadapter adapter = new simpleadapter(                     mainactivity.this, listsaller,                     r.layout.list_item, new string[] { tag_price, tag_saller_name}, new int[] { r.id.rate,                             r.id.name});              setlistadapter(adapter);         }     } } 

singlecontactactivity

public class singlecontactactivity extends activity {      // json node keys     private static final string tag_price = "price";     private static final string tag_saller_name = "name";      @override     public void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_single_contact);          // getting intent data         intent in = getintent();          // json values previous intent         string rate = in.getstringextra(tag_price);         string name = in.getstringextra(tag_saller_name);          // displaying values on screen         textview lblname = (textview) findviewbyid(r.id.name_label);         textview lblrate = (textview) findviewbyid(r.id.rate_label);          lblname.settext(name);         lblrate.settext(rate);     } } 

activity_main.xml

<linearlayout xmlns:android="http://schemas.android.com/apk/res/android"     android:layout_width="fill_parent"     android:layout_height="fill_parent"     android:orientation="vertical">     <!-- main listview           give id value list(@android:id/list)     -->     <listview         android:id="@android:id/list"         android:layout_width="fill_parent"         android:layout_height="wrap_content"/>  </linearlayout> 

activity_single_contact.xml simple linearlayout 2 textviews.