SimpleAdapter不工作

Question

行中的空指针异常：

   listView.setAdapter(sAdapter);

public class MyEmployeFragment extends Fragment {


    MyTask task;
    String employer_id;
    String employer_name;
    String str=null;
    // имена атрибутов для Map
    final String ATTRIBUTE_ID   = "p_id";
    final String ATTRIBUTE_NAME = "p_name";
    ListView listView;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                                     Bundle savedInstanceState)  {

        //myPrefs = this.getActivity().getSharedPreferences("MYsettings", Context.MODE_PRIVATE);
        task    = new MyTask();
        task.execute();

        // Creating view correspoding to the fragment
        View v = inflater.inflate(R.layout.my_employe, container, false);

        // Updating the action bar title
        getActivity().getActionBar();
        String[] userId = {"1","2","3"};

        String[] userName = {"Nadezhd","Vasya", "hardcore"};

        ArrayList<Map<String, Object>> data = new ArrayList<Map<String, Object>>(
                userId.length);
        Map<String, Object> m;
        for (int i = 0; i < userId.length; i++) {
            m = new HashMap<String, Object>();
            m.put(ATTRIBUTE_ID, userId[i]);
            m.put(ATTRIBUTE_NAME, userName[i]);
            data.add(m);
        }

        // массив имен атрибутов, из которых будут читаться данные
        String[] from = {ATTRIBUTE_ID, ATTRIBUTE_NAME};
        // массив ID View-компонентов, в которые будут вставлять данные
        int[] to = {R.id.tw_employe_id, R.id.tw_employe_name};

        // создаем адаптер
        SimpleAdapter sAdapter = new SimpleAdapter(getActivity(), data, R.layout.list_item_employee,
                from, to);


        // определяем список и присваиваем ему адаптер
        listView = (ListView) getActivity().findViewById(R.id.lv_employee_list);


       // ListView listView = (ListView) getView();
        listView.setAdapter(sAdapter);
    return v;
}



        class MyTask extends AsyncTask<Void, Void, Void> {

            @Override
            protected void onPreExecute() {

                super.onPreExecute();
            }

            @Override
            protected Void doInBackground(Void... params) {

                String s = "5ACACEC6-752B-4EFF-AA50-EEBE58A52113";
                // String user_guid = myPrefs.getString("guid", "");

                HttpActivity _http = new HttpActivity("192.168.10.11", "80");
                _http.set_addr_protocol("/WebSite/P/spr/spr.aspx/");
                _http.add_param("query", "spr_employee_get");
                // _http.add_param("p_guid", user_guid.toString().trim());
                _http.add_param("p_guid", s);
                _http.send();

                employer_name = _http.getArrayParamValue("p_name");
                employer_id = _http.getArrayParamValue("p_id");


                // массивы данных
                //String[] userId = {employer_id};

                //String[] userName = {employer_name};



            return null;
        }

            @Override
            protected void onPostExecute(Void result) {
                super.onPostExecute(result);


            }
        }

Answer 1

正如@Little Child所提到的，您的ListView是null，问题是下面的代码行：

listView = (ListView) getActivity().findViewById(R.id.lv_employee_list);

这实际上应该是：

listView = (ListView) v.findViewById(R.id.lv_employee_list);

Answer 2

从外观上看，您的listView是空的，而不是适配器。把它打印到日志中，看看你得到了什么。:)

根据Egor的答复更新：

您在Activity中拥有的是一个Fragment。因此，当您通过getActivity().findViewById()查找列表视图时，安卓将在Activity中搜索ListView，而它不会在那里找到它，因为ListView位于Fragment中。

因此，您需要使用片段的膨胀视图并使用findElementbyId()，并获得神秘的难以捉摸的ListView :)