从 JSON Android 获取数据

Question

我正在尝试将“Designacao”文本检索到列表视图，问题是我在其他数组（没有名称 BTW）中有一个数组（paises），我该怎么做？

JSON：

[
 {
   paises: [
     {
       K_PAIS: "mz",
       K_CONTINENTE: 2,
       K_LINGUAGEM: "pt",
       Designacao: "Moçambique",
       URL_IMAGE_LARGE: "/Images/large-flags/mz-large.jpg",
       URL_IMAGE_SMALL: "/Images/flags/mz.png",
       Coord_LAT: -18.4335022,
       Coord_LONG: 30.9779447,
       Coord_Zoom: 6,
       Status: "OK"
     },
     {
       K_PAIS: "ma",
       K_CONTINENTE: 2,
       K_LINGUAGEM: "pt",
       Designacao: "Marrocos",
       URL_IMAGE_LARGE: "/Images/large-flags/ma-large.jpg",
       URL_IMAGE_SMALL: "/Images/flags/ma.png",
       Coord_LAT: 31.7252847,
       Coord_LONG: -11.5777195,
       Coord_Zoom: 6,
       Status: "OK"
    },
    {
       K_PAIS: "dz",
       K_CONTINENTE: 2,
       K_LINGUAGEM: "pt",
       Designacao: "Argélia",
       URL_IMAGE_LARGE: "/Images/large-flags/dz-large.jpg",
       URL_IMAGE_SMALL: "/Images/flags/dz.png",
       Coord_LAT: 27.7538925,
       Coord_LONG: -7.3521369,
       Coord_Zoom: 5,
       Status: "OK"
    }
    ],
    K_CONTINENTE: 2,
    K_LINGUAGEM: "pt",
    Designacao: "África",
    URL_IMAGE_LARGE: "/Images/large-flags/world-large.png",
    URL_IMAGE_SMALL: "/Images/flags/world.png",
    Coord_LAT: 3.6906886,
    Coord_LONG: 12.63657,
    Coord_Zoom: 3,
    Data_Criacao: "2017-03-01T00:00:00",
    Data_Alteracao: "2017-03-01T00:00:00",
    Status: "OK"
 },
 {
 paises: [
    {
       K_PAIS: "us",
       K_CONTINENTE: 3,
       K_LINGUAGEM: "pt",
       Designacao: "Estados Unidos da América",
       URL_IMAGE_LARGE: "/Images/large-flags/us-large.jpg",
       URL_IMAGE_SMALL: "/Images/flags/us.png",
       Coord_LAT: 37.09024,
       Coord_LONG: -95.712891,
       Coord_Zoom: 4,
       Status: "OK"
    },
    {
       K_PAIS: "mx",
       K_CONTINENTE: 3,
       K_LINGUAGEM: "pt",
       Designacao: "México",
       URL_IMAGE_LARGE: "/Images/large-flags/mx-large.jpg",
       URL_IMAGE_SMALL: "/Images/flags/mx.png",
       Coord_LAT: 23.3853163,
       Coord_LONG: -111.5655016,
       Coord_Zoom: 5,
       Status: "OK"
    }
    ],
       K_CONTINENTE: 3,
       K_LINGUAGEM: "pt",
       Designacao: "América do Norte",
       URL_IMAGE_LARGE: "/Images/large-flags/world-large.png",
       URL_IMAGE_SMALL: "/Images/flags/world.png",
       Coord_LAT: 54.5259614,
       Coord_LONG: -105.2551187,
       Coord_Zoom: 4,
       Data_Criacao: "2017-03-01T00:00:00",
       Data_Alteracao: "2017-03-01T00:00:00",
       Status: "OK"
    },
{},
{},
{},
{}
]

这是mainactivity上java代码的重要部分：

                JSONArray jsonArray = new JSONArray();
                for (int i = 0; i < jsonArray.length(); i++) {
                    JSONObject jsonObj = new JSONObject(jsonStr);
                    JSONArray paises = jsonObj.getJSONArray("paises");

                    //loop
                    for (int h = 0; h < paises.length(); h++) {
                        JSONObject c = paises.getJSONObject(h);

                        String K_PAIS = c.getString("K_PAIS");
                        String Designacao = c.getString("Designcao");

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

                        pais.put("K_PAIS", K_PAIS);
                        pais.put("Designacao", Designacao);

                        listaPaises.add(pais);
                    }

                }

我的代码主要基于：http://www.androidhive.info/2012/01/android-json-parsing-tutorial/

编辑内容：

@Override
    protected Void doInBackground(Void... params) {
        HttpHandler sh = new HttpHandler();

        String jsonStr = sh.makeServiceCall(url);
        Log.e(TAG, "Response from URL: " + jsonStr);

        if (jsonStr != null) {
            try {

                JSONArray array = new JSONArray(jsonStr);
                for (int i = 0; i < array.length(); i++) {

                    JSONObject jsonObject = array.getJSONObject(i);

                    JSONArray paises = jsonObject.optJSONArray("paises");

                    if (paises != null) {
                        for (int j = 0; j < paises.length(); j++) {
                            JSONObject jsonObject1 = paises.getJSONObject(j);
                            System.out.println(jsonObject1.optString("Designacao"));
                            String K_PAIS = jsonObject1.getString("K_PAIS");
                            String Designacao = jsonObject1.getString("Designcao");

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

                            pais.put("K_PAIS", K_PAIS);
                            pais.put("Designacao", Designacao);

                            listaPaises.add(pais);
                        }
                    }
                    System.out.println(jsonObject.optString("Designacao"));
                }


            } catch (final JSONException e) {
                Log.e(TAG, "Json parsing error: " + e.getMessage());
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Toast.makeText(getApplicationContext(), "Json parsin error: " + e.getMessage(), Toast.LENGTH_LONG).show();
                    }
                });
            }
        } else {
            Log.e(TAG, "Couldn't get json from server.");
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(getApplicationContext(), "Couldn't get json from server. Check LogCat for possible errpr!", Toast.LENGTH_LONG).show();
                }
            });
        }
        return null;
    }

Answer 1

问题

1.) 您的回复是JSONArray 而不是JSONObject

new JSONObject(jsonStr); // error

2.) 您的某些JSONObjects 是空的，因此您需要检查您的JSONObject 是否包含任何paises 数组。

3.) 嵌套数组意味着嵌套循环

        // JSONArray response
        JSONArray array = new JSONArray(jsonStr);

        // traverse your array objects          
        for (int i = 0; i < array.length(); i++) {
            // fetch object one by one using index i
            JSONObject jsonObject =array.getJSONObject(i);

            // optJSONArray will give you null if there is no paises jsonArray
            JSONArray paises =jsonObject.optJSONArray("paises");

            if (paises!=null) { // nullity check
                for (int j = 0; j < paises.length(); j++) { // nested loop for paises array
                    // fetch paises array objects
                    JSONObject jsonObject1 = paises.getJSONObject(j);
                    // ahh ! this is what you were looking for 
                    // optString give you "" empty string if there is no value
                    System.out.println(jsonObject1.optString("Designacao"));
                }
            }
            // fetch value which is outside paises array
            System.out.println(jsonObject.optString("Designacao"));
        }

输出：

Moçambique
Marrocos
Argélia
Ã?frica
Estados Unidos da América
México
América do Norte

注意：避免一些奇怪的?等系统字体问题