Android解析Json对Java ArrayList的响应

Question

我正在尝试通过Volley向我的WCF服务发出GET请求，并且我想解析其对Java ArrayList响应。 这是我的方法

    public ArrayList<Company> getCompanies(){

        String url = AUDITTRACKINGAPP_SERVICE_URI + "GetCompanies";
        String tagJsonReq = "companiesRequest";

        final ProgressDialog pDialog = new ProgressDialog(context);
        pDialog.setMessage("Please Wait...");
        pDialog.show();

        final ArrayList<Company> companies = new ArrayList<Company>();

        JsonObjectRequest companiesRequest = new JsonObjectRequest(  Request.Method.GET, url, null,
                new Response.Listener<JSONObject>() {
                    @Override
                    public void onResponse(JSONObject response) {

                        Log.v(TAG, "COMPANIES RESPONSE:" + response.toString());

                        try {
                            JSONArray companiesJson = response.getJSONArray("GetCompaniesResult");

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

                                JSONObject jObject = (JSONObject)companiesJson.get(i);

                                Company company = new Company();
                                company.setCompanyId(Integer.parseInt(jObject.getString("CompanyId")));
                                Log.v(TAG, "COMPANIES setCompanyId:" + jObject.getString("CompanyId"));
                                company.setCompanyName(jObject.getString("CompanyName"));
                                Log.v(TAG, "COMPANIES setCompanyName:" + jObject.getString("CompanyName"));

                                companies.add(company);
                            }

                        } catch (JSONException e) {
                            Log.v(TAG, "COMPANIES RESPONSE ERROR ON PARSING JSON:" + e.getMessage());
                        }

                        pDialog.hide();
                    }
                },
                new Response.ErrorListener() {

                @Override
                public void onErrorResponse(VolleyError error) {
                    Log.v(TAG, "COMPANIES onErrorResponse:" + error.getMessage());
                    pDialog.hide();
                }
            });

    AppController.getInstance().addToRequestQueue(companiesRequest, tagJsonReq);

    return companies;
}

JSON响应：

 {"GetCompaniesResult":[{"CompanyId":1,"CompanyName":"CompanyName1"},{"CompanyId":2,"CompanyName":"CompanyName2"}]}

我能够获取JSON响应，但ArrayList<Company>返回null。 我认为onResponse是一个回调方法，并且在另一个线程中运行，因此我无法填充列表，但是由于我是Android新手，所以我不知道如何管理此问题。 任何帮助，将不胜感激。

Answer 1

您需要为json数组的每个元素创建json对象

try {
                            JSONArray companiesJson = response.getJSONArray("GetCompaniesResult");

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


                    JSONObject obj = Website.getJSONObject(i);


                                Company company = new Company();
                                company.setCompanyId(Integer.parseInt(obj.getString("CompanyId")));
                                Log.v(TAG, "COMPANIES setCompanyId:" + obj.getString("CompanyId"));
                                company.setCompanyName(obj.getString("CompanyName"));
                                Log.v(TAG, "COMPANIES setCompanyName:" + obj.getString("CompanyName"));

                                companies.add(company);
                            }

                        } catch (JSONException e) {
                            Log.v(TAG, "COMPANIES RESPONSE ERROR ON PARSING JSON:" + e.getMessage());
                        }

Answer 2

JsonObjectRequest 异步工作，因为主线程继续运行，并且创建了一个新线程来运行JsonObjectRequest，结果是您的返回为null。 在您的类中调用一个方法以将数据发送回并在完成对json数据的管理后调用它，例如：

public void manageCompaniesData(ArrayList<Company>){

    //YOUR CODE HERE.

}

您的代码已修改：

public ArrayList<Company> getCompanies(){

String url = AUDITTRACKINGAPP_SERVICE_URI + "GetCompanies";
        String tagJsonReq = "companiesRequest";

        final ProgressDialog pDialog = new ProgressDialog(context);
        pDialog.setMessage("Please Wait...");
        pDialog.show();

        final ArrayList<Company> companies = new ArrayList<Company>();

        JsonObjectRequest companiesRequest = new JsonObjectRequest(  Request.Method.GET, url, null,
                new Response.Listener<JSONObject>() {
                    @Override
                    public void onResponse(JSONObject response) {

                        Log.v(TAG, "COMPANIES RESPONSE:" + response.toString());

                        try {
                            JSONArray companiesJson = response.getJSONArray("GetCompaniesResult");

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

                                JSONObject jObject = (JSONObject)companiesJson.get(i);

                                Company company = new Company();
                                company.setCompanyId(Integer.parseInt(jObject.getString("CompanyId")));
                                Log.v(TAG, "COMPANIES setCompanyId:" + jObject.getString("CompanyId"));
                                company.setCompanyName(jObject.getString("CompanyName"));
                                Log.v(TAG, "COMPANIES setCompanyName:" + jObject.getString("CompanyName"));

                                companies.add(company);
                            }

                        } catch (JSONException e) {
                            Log.v(TAG, "COMPANIES RESPONSE ERROR ON PARSING JSON:" + e.getMessage());
                        }
                        manageCompaniesData(companies);
                        pDialog.hide();
                    }
                },
                new Response.ErrorListener() {

                @Override
                public void onErrorResponse(VolleyError error) {
                    Log.v(TAG, "COMPANIES onErrorResponse:" + error.getMessage());
                    pDialog.hide();
                }
            });

    AppController.getInstance().addToRequestQueue(companiesRequest, tagJsonReq);

    }

Answer 3

JSONArray对象具有函数getJSONObject(int index)因此您必须使用

JSONObject jObject = companiesJson.getJSONObject(i);

代替

JSONObject jObject = (JSONObject)companiesJson.get(i);

试试这个代码。

for (int i = 0; i < companiesJson.length(); i++) {
  JSONObject jObject = companiesJson.getJSONObject(i);
  Company company = new Company();
  company.setCompanyId(jObject.getInt("CompanyId")));
  company.setCompanyName(jObject.getString("CompanyName"));
  companies.add(company);
 }

代替

for (int i = 0; i < companiesJson.length(); i++) {
  JSONObject jObject = (JSONObject)companiesJson.get(i);
  Company company = new Company();
  company.setCompanyId(Integer.parseInt(jObject.getString("CompanyId")));
  Log.v(TAG, "COMPANIES setCompanyId:" + jObject.getString("CompanyId"));
  company.setCompanyName(jObject.getString("CompanyName"));
  Log.v(TAG, "COMPANIES setCompanyName:" + jObject.getString("CompanyName"));

  companies.add(company);
 }

Answer 4

在for循环内像这样解析json。也不要将ArrayList公司声明为final 。

Company company = new Company();
JSONObject jObject = (JSONObject)companiesJson.optJSONObject(i); 
if(jObject != null){ 
   company.setCompanyId(jObject.optInt("CompanyId")));
   company.setCompanyName(jObject.optString("CompanyName"));
}

Answer 5

如果您想为CompanyID和CompanyName设置json值，请尝试以下代码段。 for（int i = 0; i <companiesJson.length（）; i ++）{

                        JSONObject jObject = companiesJson.getJSONObject(i);
                        Company company = new Company();
                        company.setCompanyId(Integer.parseInt(jObject.getString("CompanyId")));
                        Log.v(TAG, "COMPANIES setCompanyId:" + jObject.getString("CompanyId"));
                        company.setCompanyName(jObject.getString("CompanyName"));
                        Log.v(TAG, "COMPANIES setCompanyName:" + jObject.getString("CompanyName"));
                        companies.add(company);

Answer 6

如果您在logcat中收到任何JSON异常，请尝试一次。

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

                            JSONObject jObject = companiesJson.getJSONObject(i);
                            Company company = new Company();
                            company.setCompanyId(Integer.parseInt(jObject.getString("CompanyId")));
                            Log.v(TAG, "COMPANIES setCompanyId:" + jObject.getString("CompanyId"));
                            company.setCompanyName(jObject.getString("CompanyName"));
                            Log.v(TAG, "COMPANIES setCompanyName:" + jObject.getString("CompanyName"));
                            companies.add(company);
 }