android JSON in ListFragment -

i'm new android development. i've no problem json when used in mainactivity got problem when move code listfragment

this line nothing happen: jsonobject json = userfunctions.announcementfeed(myid, mytype);

here full code:

package com.example.demo123; import java.util.arraylist; import java.util.hashmap; import library.userfunctions; import org.json.jsonarray; import org.json.jsonexception; import org.json.jsonobject; import android.os.bundle; import android.support.v4.app.listfragment; import android.util.log; import android.view.layoutinflater; import android.view.view; import android.view.viewgroup; import android.widget.simpleadapter;  public class announcementlist extends listfragment { private static final string tag = "myannouncement";   jsonarray announcementlist = null;             userfunctions userfunctions;  string myid = mainactivity.myid; string mytype = mainactivity.mytype;  @override public view oncreateview(layoutinflater inflater, viewgroup container,bundle savedinstancestate) {           return super.oncreateview(inflater, container, savedinstancestate); }  @override public void onactivitycreated(bundle savedinstancestate) {     log.i(tag,"start announcement list");      arraylist<hashmap<string, string>> theannnouncement = new arraylist<hashmap<string, string>>();     jsonobject json = userfunctions.announcementfeed(myid, mytype);      try {         if (json.getstring("success") != null) {             announcementlist = json.getjsonarray("announcedt");             (int = 0; < announcementlist.length(); i++) {                 jsonobject c = announcementlist.getjsonobject(i);                 string title = c.getstring("topic");                 string course = c.getstring("course") + " - " + c.getstring("coursetitle");                 string created = "by " + c.getstring("entered_by") + " | " + c.getstring("entry_date");                  hashmap<string, string> map = new hashmap<string, string>();                 map.put("title", title);                 map.put("course", course);                 map.put("created", created);                  theannnouncement.add(map);             }         }                     } catch (jsonexception e) {         e.printstacktrace();     }      string[] = { "title","course","created" };     int[] = { r.id.title,r.id.course,r.id.created};      simpleadapter adapter = new simpleadapter(getactivity().getbasecontext(), theannnouncement, r.layout.list_item, from, to);                 setlistadapter(adapter);         } 

}

why absolutely necessary put logic in onactivitycreated? fragment not initialized @ point might want move logic onresume or somewhere else.

edit: took @ code linked, announcementfeed() method.

it looks you're trying networking on main thread, method;

public jsonobject announcementfeed(string username, string usertype){     ..................................      jsonobject json = jsonparser.getjsonfromurl(loginurl, params);     // return json     return json; } 

you're calling method in onactivitycreated. suggest moving background thread or asynctask. still, without logcat can't 100% sure what's happening, @ least we're able point out off top.