simpleAdapter在構造函數中顯示錯誤

Question

我在代碼中遇到問題。我在這段代碼中嘗試了很多東西，但是它沒有修復。最後描述錯誤。這是與構造函數有關的東西。

SelectActivityAnswer.java

package com.example.test; 


import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStream; 
import java.io.InputStreamReader; 
import java.util.ArrayList; 
import java.util.HashMap; 
import java.util.List; 
import java.util.Map; 

import org.apache.http.HttpResponse; 
import org.apache.http.client.ClientProtocolException; 
import org.apache.http.client.HttpClient; 
import org.apache.http.client.methods.HttpPost; 
import org.apache.http.impl.client.DefaultHttpClient; 
import org.json.JSONArray; 
import org.json.JSONException; 
import org.json.JSONObject; 


import android.app.Fragment; 
import android.os.AsyncTask; 
import android.os.Bundle; 

import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.ListView; 
import android.widget.SimpleAdapter; 
import android.widget.Toast; 





public class SelectAnswerActivity extends Fragment { 
    final static String ARG_POSITION_ANSWER = "position"; 
    private String jsonResult; 
    private String url = "http://myip/employee_details.php"; 
    private ListView listView; 


    public SelectAnswerActivity() { 
     // Empty constructor required for fragment subclasses 


    } 



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

     //SimpleAdapter simpleAdapter = new SimpleAdapter(this, null, 0, null, null); 
     View rootView = inflater.inflate(R.layout.activity_select_answer, container, false); 

     accessWebService(); 


    // selectListAns = (ListView) rootView.findViewById(R.id.ans_list); 
     // novo code abaixo 
     // ListAdapterAns adapterAns = new ListAdapterAns(this,toppings); 
    // selectListAns.setAdapter(adapterAns); 
    // selectListAns.setOnItemClickListener(new AnsItemClickListener()); 

     //View rootView = inflater.inflate(R.layout.activity_select_answer, container, false); 
     //int i = getArguments().getInt(ARG_PLANET_NUMBER); 
     //String planet = getResources().getStringArray(R.array.planets_array)[i]; 

     //int imageId = getResources().getIdentifier(planet.toLowerCase(Locale.getDefault()), 
        // "drawable", getActivity().getPackageName()); 
     // ((ImageView) rootView.findViewById(R.id.image)).setImageResource(imageId); 
     // getActivity().setTitle(planet); 
     return rootView; 
    } 

// Async Task to access the web 
    private class JsonReadTask extends AsyncTask<String, Void, String> { 
     @Override 
     protected String doInBackground(String... params) { 
      HttpClient httpclient = new DefaultHttpClient(); 
      HttpPost httppost = new HttpPost(params[0]); 
      try { 
       HttpResponse response = httpclient.execute(httppost); 
       jsonResult = inputStreamToString(
         response.getEntity().getContent()).toString(); 
      } 

      catch (ClientProtocolException e) { 
       e.printStackTrace(); 
      } catch (IOException e) { 
       e.printStackTrace(); 
      } 
      return null; 
     } 



     private StringBuilder inputStreamToString(InputStream is) { 
      String rLine = ""; 
      StringBuilder answer = new StringBuilder(); 
      BufferedReader rd = new BufferedReader(new InputStreamReader(is)); 

      try { 
       while ((rLine = rd.readLine()) != null) { 
        answer.append(rLine); 
       } 
      } 

      catch (IOException e) { 
       // e.printStackTrace(); 
       //Toast.makeText(getApplicationContext(), 
       //  "Error..." + e.toString(), Toast.LENGTH_LONG).show(); 
      } 
      return answer; 
     } 

     @Override 
     protected void onPostExecute(String result) { 
      ListDrwaer(); 
     } 
    }// end async task 

    public void accessWebService() { 
     JsonReadTask task = new JsonReadTask(); 
     // passes values for the urls string array 
     task.execute(new String[] { url }); 
    } 

    // build hash set for list view 
    public void ListDrwaer() { 
     List<Map<String, String>> employeeList = new ArrayList<Map<String, String>>(); 

     try { 
      JSONObject jsonResponse = new JSONObject(jsonResult); 
      JSONArray jsonMainNode = jsonResponse.optJSONArray("emp_info"); 

      for (int i = 0; i < jsonMainNode.length(); i++) { 
       JSONObject jsonChildNode = jsonMainNode.getJSONObject(i); 
       String name = jsonChildNode.optString("employee name"); 
       String number = jsonChildNode.optString("employee no"); 
       String outPut = name + "-" + number; 
       employeeList.add(createEmployee("employees", outPut)); 
      } 
     } catch (JSONException e) { 
      //Toast.makeText(getApplicationContext(), "Error" + e.toString(), 
      //  Toast.LENGTH_SHORT).show(); 
     } 

     SimpleAdapter simpleAdapter = new SimpleAdapter(this, employeeList, 
       R.id.content_list_ans, 
       new String[] { "employees" }, new int[] { android.R.id.text1 }); 
     listView.setAdapter(simpleAdapter); 
     //Toast.makeText(getApplication(), "c", Toast.LENGTH_SHORT).show(); 

    } 

    private HashMap<String, String> createEmployee(String name, String number) { 
     HashMap<String, String> employeeNameNo = new HashMap<String, String>(); 
     employeeNameNo.put(name, number); 
     return employeeNameNo; 
    } 

} 

該生產線是：

SimpleAdapter simpleAdapter = new SimpleAdapter(this, employeeList, 
       R.id.content_list_ans, 
       new String[] { "employees" }, new int[] { android.R.id.text1 }); 
     listView.setAdapter(simpleAdapter); 

的錯誤是：

The constructor SimpleAdapter(SelectAnswerActivity, List<Map<String,String>>, int, String[], int[]) is 
undefined. 

該問題是這個（上下文）？

Answer 1

試試這個，使用活動情境，而不是片段

SimpleAdapter simpleAdapter = new SimpleAdapter(getActivity(), employeeList, 
      R.id.content_list_ans, 
      new String[] { "employees" }, new int[] { android.R.id.text1 }); 

Answer 2

您對Context參考是錯誤的。您不能在AsynTask類中擁有活動上下文。您應該嘗試使用getApplicationContext()或getActivity()而不是this。

另外SelectAnswerActivity不是和Activity，它的一個Fragment。如果是活動，您也可以使用SelectAnswerActivity.this

Answer 3

您正在引用片段的上下文，而不是您的活動之一。試着改變它。