无法在片段中显示列表视图

Question

我有以下代码： -

public class ByState extends Fragment {
    List<LegislatorByState> bystate= new ArrayList<LegislatorByState>();


    @Nullable
    @Override

    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.by_state, container, false);
        new GetAllStates().execute("dummy");
        ArrayAdapter adapter = new ArrayAdapter<LegislatorByState>(getActivity(), R.layout.bystate_itemview, bystate);
        ListView list = (ListView) rootView.findViewById(R.id.state_listView);
        list.setAdapter(adapter);
        return rootView;
    }
    public void populateList(String bioguide, String lastname,String firstname,String party,String statename,String district ){
        bystate.add(new LegislatorByState(bioguide, lastname, firstname, party, statename, district));
        Log.d("bio",bioguide);
    }
}

class LegislatorByState{
    public String lastname;
    public String firstname;
    public String bioguide;
    public String statename;
    public String district;
    public String party;

    public LegislatorByState(String lastname, String firstname, String bioguide, String statename, String district, String party) {
        this.lastname = lastname;
        this.firstname = firstname;
        this.bioguide = bioguide;
        this.statename = statename;
        this.district = district;
        this.party = party;
    }
    public void display(){
        ByState obj=new ByState();
        obj.populateList(this.bioguide,this.lastname,this.firstname,this.party,this.statename,this.district);
    }
}


class GetAllStates extends AsyncTask<String,String,JsonReader> {
    @Override
    protected JsonReader doInBackground(String... key) {
        JsonReader reader=null;
        try {
            String url = "http://congress-search-148802.appspot.com/getData.php?value=legislator";
            URL obj = new URL(url);
            HttpURLConnection con = (HttpURLConnection) obj.openConnection();
            con.setRequestMethod("GET");
            int responseCode = con.getResponseCode();
            reader = new JsonReader(new InputStreamReader(con.getInputStream()));
        } catch (Exception e) {
            Log.w("Error", e.getMessage());
        }
        return reader;
    }
    @Override
    protected void onPostExecute(JsonReader reader) {
        LegislatorByState object = null;
        try {
            reader.beginObject();
            while (reader.hasNext()) {
                    String name = reader.nextName();
                if (name.equals("results")){
                    reader.beginArray();
                    while (reader.hasNext()) {
                        reader.beginObject();
                        while (reader.hasNext()) {
                            String id = reader.nextName();
                            if(id.equals("bioguide_id")){
                                if(object != null) {object.display();}
                                object = new LegislatorByState(null,null,null,null,null,null);
                                String bioguide_id=reader.nextString();
                                object.bioguide=bioguide_id;
                                }
                            else if(id.equals("last_name")){
                                String lastname=reader.nextString();
                                object.lastname=lastname;
                            }
                            else if(id.equals("first_name")){
                                String firstname=reader.nextString();
                                object.firstname=firstname;
                            }
                            else if(id.equals("party")){
                                String party=reader.nextString();
                                object.party=party;
                            }
                            else if(id.equals("state_name")){
                                String statename=reader.nextString();
                                object.statename=statename;
                            }
                            else if(id.equals("district")){
                                if (reader.peek() == JsonToken.NULL){
                                    reader.skipValue();
                                    object.district="NA";
                                }
                                else{
                                String district=reader.nextString();
                                    object.district=district;
                                }
                            }
                            else
                                reader.skipValue();
                            //object.display();
                        }reader.endObject();
                    }reader.endArray();
                }

                else {
                    reader.skipValue();
                }
                    }reader.endObject();


        }
        catch (IOException e){
            Log.w("Error",e.getMessage());
        }

    //object.display(obj);

    }
}

我能够获得正确的数据，但无法在列表视图中显示它。有人可以请你帮我一个新的。我无法掌握如何在片段中显示列表视图的概念。