Php 在AsyncTask中执行doInBackground（）时出错

嗨，我正在使用

AsyncTask

从php文件中获取数据，但是当我运行应用程序时，我得到了这个错误

List<Online_Messages_item> o;
public class RequestPostsTask extends AsyncTask<Void, Void, Boolean> {
        ProgressDialog pdLoading;


        @Override
        protected void onPreExecute() {
            pdLoading = new ProgressDialog(Messages_online.this);
            pdLoading.setProgressStyle(ProgressDialog.STYLE_SPINNER);
            pdLoading.setMessage("please wait ...");
            pdLoading.setIndeterminate(false);
            pdLoading.setCancelable(false);
            pdLoading.show();
        }

        @Override
        protected Boolean doInBackground(Void... params) {
            boolean status = false; 
            HttpURLConnection urlConnection = null;

            try {
                URL url = new URL("my url");

                urlConnection = (HttpURLConnection) url.openConnection();
                Charset charset = Charset.forName("UTF8");
                int responseCode = urlConnection.getResponseCode();

                if (responseCode == HttpURLConnection.HTTP_OK) {
                    BufferedReader in = new BufferedReader(new InputStreamReader(urlConnection.getInputStream(), charset));
                    if (in != null) {
                        StringBuilder strBuilder = new StringBuilder();
                        int ch = 0;
                        while ((ch = in.read()) != -1)
                            strBuilder.append((char) ch);
                        String response = strBuilder.toString();
                        Log.d("Server response:", response);

                        JSONObject jObject = new JSONObject(response);
                        JSONArray jsonArray = jObject.getJSONArray("posts");
                        for(int i=0; i<jsonArray.length(); i++){
                            Online_Messages_item omi = new Online_Messages_item();
                            omi.setId(jsonArray.getJSONObject(i).getLong("ID"));
                            omi.settext(jsonArray.getJSONObject(i).getString("Text"));
                            omi.setlikes(jsonArray.getJSONObject(i).getString("Likes"));
                            omi.setpt(jsonArray.getJSONObject(i).getString("PublishTime"));
                            o.add(omi);
                        }
                        if(o.size() >= 1)
                            status = true;
                    }

                    in.close();
                }
            }
            catch(MalformedURLException e){
                e.printStackTrace();
            }
            catch (IOException e) {
                e.printStackTrace();
            }
            catch (JSONException e) {
                e.printStackTrace();
            }
            finally {
                urlConnection.disconnect();
            }

            return status;
        }

        @Override
        protected void onPostExecute(Boolean result) {
            BaseAdapter ba=new Messages_online_adapter(Messages_online.this,o);
            listView.setAdapter(ba);
            pdLoading.dismiss();

        }
    }

有什么帮助吗？提前谢谢

列表o；
List<Online_Messages_item> o;

您从不初始化

o

---

你应该把

o=newarraylist（）放在某个地方。我建议使用构造函数
Mahfa正如blackbelt建议的那样，您需要向RequestPostsTask类添加一个构造函数。只需向类中添加以下代码行，就可以了：）

public RequestPostsTask（）{o=new ArrayList（）；}
第80行是什么
Messages\u online.java
？@Raghunandan这是一项活动第80行是什么。您能在代码中指出行号80吗？stacktrace指向doInBackground。我查了一下那里的“代码”@Raghunandan@blackbelt不可否认。
List<Online_Messages_item> o;

public RequestPostsTask(){ o = new ArrayList<Online_Messages_item>(); }