java - Stuck on Android.os.Bundle with Null Object Reference -

i don't know why error happens. have checked code link 1 still doesn't give solution.

the ide gimme error :

java.lang.nullpointerexception: attempt invoke virtual method 'int android.os.bundle.getint(java.lang.string)' on null object reference @ com.gook.rebill.fragment.homefragment.onattach(homefragment.java:74)

i know it's null object reference, still don't cause of error.

please me.

this code :

    public class homefragment extends fragment implements internetconnectionlistener, apihandler.apihandlerlistener {      private static final string arg_section_number = "section_number";     private final int category_action = 1;     private categoryselectioncallbacks mcallbacks;     private arraylist<category> categorylist;     private listview categorylistview;     private string error = null;     private internetconnectionlistener internetconnectionlistener;      public homefragment() {      }      public static homefragment newinstance(int sectionnumber) {         homefragment fragment = new homefragment();         bundle args = new bundle();         args.putint(arg_section_number, sectionnumber);         fragment.setarguments(args);         return fragment;     }      @override     public void onattach(activity activity) {         super.onattach(activity);         ((homeactivity) activity).onsectionattached(getarguments().getint(arg_section_number));         try {             mcallbacks = (categoryselectioncallbacks) activity;         } catch (classcastexception e) {             throw new classcastexception("activity must implement categoryselectioncallbacks.");         }     }      @override     public view oncreateview(layoutinflater inflater, viewgroup container,                              bundle savedinstancestate) {         view rootview = inflater.inflate(r.layout.fragment_home, container, false);         categorylistview = (listview) rootview.findviewbyid(r.id.categorylistview);         return rootview;     }      @override     public void onresume() {         super.onresume();         if (utilmethods.isconnectedtointernet(getactivity())) {             initcategorylist();         } else {             internetconnectionlistener = (internetconnectionlistener) homefragment.this;             shownointernetdialog(getactivity(), internetconnectionlistener,                     getresources().getstring(r.string.no_internet),                     getresources().getstring(r.string.no_internet_text),                     getresources().getstring(r.string.retry_string),                     getresources().getstring(r.string.exit_string), category_action);         }      }      public class getcateglist extends asynctask<void, void, void>{          @override         protected void doinbackground(void... params) {              /**              * json populating text file. make api call use apihandler class              *              *  <code>apihandler apihandler = new apihandler(this, url_get_category);</code> <br>              *  <code>apihandler.doapirequest(apihandler.request_get);</code> <br>              *              * response in onsuccessresponse(string tag, string jsonstring) method              * if successful api call has done. parsing following.              */             url hp = null;             try {                 hp = new url(                         getstring(r.string.liveurl) + "foodcategory.php");                  log.d("url", "" + hp);                 urlconnection hpcon = hp.openconnection();                 hpcon.connect();                 inputstream input = hpcon.getinputstream();                  bufferedreader r = new bufferedreader(new inputstreamreader(input));                  string x = "";                 x = r.readline();                 string total = "";                  while (x != null) {                     total += x;                     x = r.readline();                 }                 log.d("ur1l", "" + total);                  jsonarray j = new jsonarray(total);                  log.d("url1", "" + j.length());                    categorylist = new arraylist<category>();                  (int = 0; < j.length(); i++) {                     category category = new category();// buat variabel category                     jsonobject obj;                     obj = j.getjsonobject(i); //sama sperti yang lama, cman ini lebih mempersingkat karena getjsonobject cm d tulis sekali aja disini                      category.setid(obj.getstring(jf_id));                     category.settitle(obj.getstring(jf_title));                     category.seticonurl(obj.getstring(jf_icon));                      if (!textutils.isempty(obj.getstring(jf_background_image))) {                         category.setimageurl(obj.getstring(jf_background_image));                     }                     log.d("url1",""+obj.getstring(jf_title));                     categorylist.add(category);                 }                  getactivity().runonuithread(new runnable() {                     @override                     public void run() {                         categorylistview.setadapter(new categoryadapter(getactivity(), mcallbacks, categorylist));                     }                 });                }catch (malformedurlexception e) {                 // todo auto-generated catch block                 e.printstacktrace();                 error = e.getmessage();             } catch (ioexception e) {                 // todo auto-generated catch block                 e.printstacktrace();                 error = e.getmessage();             } catch (jsonexception e) {                 // todo auto-generated catch block                 error = e.getmessage();                 e.printstacktrace();             } catch (nullpointerexception e) {                 // todo: handle exception                 error = e.getmessage();             }             return null;         }     }        //! function populate category list     private void initcategorylist() {             new getcateglist().execute();     }      @override     public void onconnectionestablished(int code) {         if (code == category_action) {             initcategorylist();         }     }      @override     public void onusercanceled(int code) {         if (code == category_action) {             getactivity().finish();         }     }      //! catch json response here     @override     public void onsuccessresponse(string tag, string jsonstring) {         //! same parsing done in initcategorylist()     }      //! detect response error here     @override     public void onfailureresponse(string tag) {      }      //! callback interface listen homeactivity detect user click on category     public static interface categoryselectioncallbacks {         void oncategoryselected(string catid, string title);     } } 

here use fragment code, in homeactivity:

 public void onsectionattached(int number) {     switch (number) {         case 1:             mtitle = getstring(r.string.title_section1);             break;         case 2:             mtitle = getstring(r.string.title_section2);             break;         case 3:             mtitle = getstring(r.string.title_section3);             break;     } } 

i think getarguments() return null.
can see these example:
android fragment getarguments() returns null
fragment getarguments() returns null