变量返回null，外面的AsyncTask的android [英] variable returns null outside asynctask android

问题描述

我有过PHP获取数据的AsyncTask的。该AsyncTask的做工精细，它传递的值，以一个全球性的数组列表。然而，当我尝试.execute（）之后调用上的onCreate变量，它返回一个空尺寸/值（S）。我想知道为什么当它应该有一个值这个全局变量返回null。在此先感谢！

这是code为asyntask：

 私有类get_pendingreq扩展的AsyncTask＆LT;字符串，整数，字符串＆GT;
 {
    @覆盖
    保护字符串doInBackground（字符串...为arg0）
    {
        InputStream为= NULL;
        字符串结果=;        尝试
        {
            HttpClient的HttpClient的=新DefaultHttpClient（）;
            HttpPost httppost =新HttpPost（URL +pending_requests.php）;            清单＆LT;＆的NameValuePair GT;参数=新的ArrayList＆LT;＆的NameValuePair GT;（）;
            parameter.add（新BasicNameValuePair（电子邮件，globalVariables.accountemail））;
            httppost.setEntity（新UrlEn codedFormEntity（参数））;            HTT presponse响应= httpclient.execute（httppost）;
            HttpEntity实体= response.getEntity（）;
            是= entity.getContent（）;        }赶上（例外五）
        {
            Log.e（log_tag，在HTTP连接错误+ e.toString（））;
        }        尝试
        {
            读者的BufferedReader =新的BufferedReader（
                    新InputStreamReader的（是ISO-8859-1），8）;
            StringBuilder的SB =新的StringBuilder（）;
            串线= NULL;            而（（行= reader.readLine（））！= NULL）
            {
                sb.append（行+\\ n）;
            }
            is.close（）;
            结果= sb.toString（）;
        }赶上（例外五）
        {
            Log.e（log_tag，错误转换结果+ e.toString（））;
        }        返回结果;
    }    @覆盖
    保护无效onPostExecute（字符串结果）
    {
        super.onPostExecute（结果）;        尝试
        {
            / * JSON解析从这里开始* /
            JSONObject的jArray =新的JSONObject（结果）;
            /*globalVariables.pendingdate =新的ArrayList＆LT;串GT;（）; * /
            JSONArray请求= jArray.getJSONArray（请求）;            的for（int i = 0; I＆LT; request.length（）;我++）
            {                JSONObject的E = request.getJSONObject（I）                / *把值的ArrayList＆LT;串GT; * /
                globalVariables.pendingdate.add（e.getString（DATE））;            }            Log.d（striiing，globalVariables.pendingdate.toString（））;
        }赶上（JSONException E）
        {
            e.printStackTrace（）;
                }
    }
}
 

主要活动：

 公共无效的onCreate（捆绑savedInstanceState）{
    super.onCreate（savedInstanceState）;
    的setContentView（R.layout.calendar）;    新get_pendingreq（）执行（）;    System.out.print（alalala+ globalVariables.pendingdate.size（））;
      } //返回null
 

全局变量：

 公共静态的ArrayList＆LT;串GT; pendingdate =新的ArrayList＆LT;弦乐取代;
 

解决方案

由于的AsyncTask 没有完成。把 System.out.print（完成）; 在 onPostExcute（），看看谁最先打印

I have an asynctask which gets its data through php. The asynctask works fine, it passes the values to a global arraylist. However, when i try to call the variable on onCreate after .execute(), it returns a null size/value(s). I would like to know why this global variable returns a null when its supposed to have a value. Thanks in advance!

this is the code for asyntask:

 private class  get_pendingreq extends AsyncTask<String, Integer, String> 
 {
    @Override
    protected String doInBackground(String... arg0) 
    {
        InputStream is = null;
        String result = "";

        try 
        {
            HttpClient httpclient = new DefaultHttpClient();
            HttpPost httppost = new HttpPost(url+"pending_requests.php");

            List<NameValuePair> parameter = new ArrayList<NameValuePair>();
            parameter.add(new BasicNameValuePair("email", globalVariables.accountemail));


            httppost.setEntity(new UrlEncodedFormEntity(parameter));

            HttpResponse response = httpclient.execute(httppost);
            HttpEntity entity = response.getEntity();
            is = entity.getContent();

        } catch (Exception e) 
        {
            Log.e("log_tag", "Error in http connection " + e.toString());
        }

        try 
        {
            BufferedReader reader = new BufferedReader(
                    new InputStreamReader(is, "iso-8859-1"), 8);
            StringBuilder sb = new StringBuilder();
            String line = null;

            while ((line = reader.readLine()) != null) 
            {
                sb.append(line + "\n");
            }
            is.close();
            result = sb.toString();
        } catch (Exception e) 
        {
            Log.e("log_tag", "Error converting result " + e.toString());
        }

        return result;
    }

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

        try 
        {
            /*  JSON parsing starts here    */
            JSONObject jArray = new JSONObject(result);
            /*globalVariables.pendingdate = new ArrayList<String>();*/
            JSONArray request = jArray.getJSONArray("request");

            for (int i = 0; i < request.length(); i++) 
            {

                JSONObject e = request.getJSONObject(i);

                /* puts values to arraylist<String>  */                 
                globalVariables.pendingdate.add(e.getString("date"));

            }

            Log.d("striiing", globalVariables.pendingdate.toString());
        } catch (JSONException e) 
        {
            e.printStackTrace();
                }
    }
}

Main activity:

    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.calendar);

    new get_pendingreq().execute();

    System.out.print("alalala" + globalVariables.pendingdate.size());
      }//this returns null

Global Variable:

public static ArrayList<String> pendingdate = new ArrayList<String>;

解决方案

Because AsyncTask not finished. Put System.out.print("finish"); in onPostExcute() and see who is printed first.

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