Question

更新：我通过HashMap填充数组，Iam使用Asynctask获取http请求＆amp;填充数组后将该数组放入对话框中。当我第一次运行我的应用程序时，它给了我一个空的对话框＆amp;没有给出任何错误但是当我重新运行我的应用程序时，它完美地显示了对话框中的所有数组元素。是什么原因？

//JsonResponse Inner Class in main class

private class JsonResponse extends AsyncTask<String, Void, String> {

        String response = "";
private ArrayList<HashMap<String, String>> prServices_resultList = new ArrayList<HashMap<String, String>>();
        protected void onPreExecute() 
        {

        }

        protected void onPostExecute(String result) 
        {   
            if(response.equalsIgnoreCase("Success"))
            {
            ResultList_List = prServices_resultList;    

            int z=0;

    for (HashMap<String, String> hashList : prServices_resultList)
             {
    Av_List[z] = hashList.get(android_Av_ID);

    Av_Lat[z]  = Double.parseDouble(hashList.get(android_Av_LAT));

    Av_Lng[z]  = Double.parseDouble(hashList.get(android_Av_LONG));

                z++;
            }  
            }
        }
        protected String doInBackground(final String... args)
        {    
            JSONParser jParser = new JSONParser();

            JSONArray jArrayServices = jParser.getJSONFromUrl(url_Services);

            try{
                for (int i = 0; i < jArrayServices.length(); i++) 
                {
            JSONObject jsonElements = jArrayServices.getJSONObject(i);

            String S_id = jsonElements.getString(android_S_ID);

            String S_name = jsonElements.getString(android_S_NAME);

        HashMap<String, String> hashServices = new HashMap<String, String>();

                    // adding each child node to HashMap key
                    hashServices.put(android_S_ID, S_id);
                    hashServices.put(android_S_NAME, S_name);

                    // adding HashList to ArrayList
                    prServices_resultList.add(hashServices);
                }

                    response = "Success";
            }
                catch(JSONException e)
                    {
                        e.printStackTrace();
                    }

                return response;
        }
    }

在我按下按钮时的主课：

new JsonResponse().execute;

在上面的主要课上onCreate我声明如下：

 static ArrayList<HashMap<String, String>> ResultList_Services = new ArrayList<HashMap<String, String>>();

String[] Db_Services  =  new String[ResultList_Services.size()];

    String[] Db_ServicesID  =  new String[ResultList_Services.size()];

现在我收到一个错误：java.lang.ArrayIndexOutOfBoundsException：length = 0;索引= 0

Answer 1

首先，将值添加到可从后台线程访问UI线程的静态字段ResultList_Services是非常糟糕的做法。您应该将代码重写为线程安全的。有几个选项，一个是：

private class JsonResponse extends AsyncTask<String, Void, String> {

    private ArrayList<HashMap<String, String>> resultList = new ArrayList<HashMap<String, String>>();

    ...

    protected String doInBackground(final String... args)
    {
        ...

        // adding HashList to private JsonResponse's field
        resultList.add(hashServices);

        ...
    }

    protected void onPostExecute(String result) 
    {   
        if (response.equalsIgnoreCase("Success"))
        {
            ResultList_Services = resultList;
            //TODO: notify your Activity/Dialog on completion
        }
    }
}

关于您的问题 - 没有看到新记录的原因是您在ResultList中没有值时显示对话框。例如，您应该要求onPostExecute显示它。

Answer 2

你需要这样做 -

for (HashMap<String, String> hashServices : ResultList_Services)
         {
            Db_Services[s] = hashServices.get(android_S_CName);

            Db_ServicesID[s] = hashServices.get(android_S_ID);
            s++;
        }

在asynctask的 onPostExecute（）块中。

使用HashMap填充数组<string，string =“”> </string，>

2 个答案: