如何正确解析此JSON？

Question

I have a big JSON file that contains Countries, States and Cities. The JSON looks like this:

{
"Countries":[
        {
        "CountryName":"India",
        "States":[
                    {
                    "StateName":"Maharashtra",
                    "Cities":[
                            "Pune",
                            "Nagpur",
                            "Mumbai"
                              ]
                     },
                     {
                     "StateName":"Kerala",
                     "Cities":[
                                "Kochi",
                                "Munnar"
                              ]
                      }
                   ]
         },
         {
          "CountryName":"Australia",
          "States":[
                    {
                    "StateName":"Aukland",
                    "Cities":[
                            "GlenField",
                            "Henderson",
                                "MilFord"
                              ]
                     },
                     {
                     "StateName":"Melbourne",
                     "Cities":[
                                "Melbourne",
                                "South Oakleigh"
                              ]
                      }
                   ]
          }
       ]
  }

I have an activity in my app that requires the user to select a country and upon selecting a country I want to get all the states of that country as an array list. And when a specific state is selected, I want to get all the cities of that state as an array list.

I am able to get a list of all Countries using this method:

public void loadCountries(String parent, String child, ArrayList<String> listValue)
{
    try {
        JSONObject obj = new JSONObject(loadJSONFromAsset());
        JSONArray m_jArry = obj.getJSONArray(parent);;
        ArrayList<HashMap<String, String>> formList = new ArrayList<HashMap<String, String>>();
        HashMap<String, String> m_li;

      //  listValue = new ArrayList<>();


        for (int i = 0; i < m_jArry.length(); i++) {
            JSONObject jo_inside = m_jArry.getJSONObject(i);
            Log.d("Details-->", jo_inside.getString(child));
            listValue.add(jo_inside.getString(child));
        }


    } catch (JSONException e) {
        e.printStackTrace();
    }
}

public String loadJSONFromAsset() {
    String json = null;
    try {
        InputStream is = getAssets().open("Contries.json");
        int size = is.available();
        byte[] buffer = new byte[size];
        is.read(buffer);
        is.close();
        json = new String(buffer, "UTF-8");
    } catch (IOException ex) {
        ex.printStackTrace();
        return null;
    }
    return json;
}

Then, in the onCreate method, using this line gives me all the countries in an array list

loadCountries("Countries", "CountryName", countries);

Since this is my first time working with a JSON file in AndroidStudio/Java, I have no idea what to do to get the states and the cities. Any help is greatly appreciated.

Answer 1

You could use GSON library. Just create corresponding java object which will reflect json structure and do like here:

MyClass data = new Gson().fromJson(json, MyClass.class);

Answer 2

Respect for trying to do this yourself, but we live in the age of the API. Check out Google's GSON library, it parses JSON to java objects, and java objects to JSON. It's one of the most useful APIs out there. https://github.com/google/gson

Answer 3

Try this:

 Map<String, Map<String, Map<Integer, String>>> data = new HashMap<>();

              try {
                JSONObject object = new JSONObject(loadJSONFromAsset());
                JSONArray countries = object.getJSONArray("Countries");

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

                    JSONObject state = countries.getJSONObject(i);
                    JSONArray statesList = state.getJSONArray("States");
                    String countryName = countries.getJSONObject(i).getString("CountryName");

                    for (int j = 0; j < statesList.length(); j++) {

                        JSONObject city = statesList.getJSONObject(j);
                        JSONArray citiesList = city.getJSONArray("Cities");
                        String stateName = city.getString("StateName");

                        Map<String, Map<Integer, String>> stateHashMap = new HashMap<>();

                        for (int k = 0; k < citiesList.length(); k++) {

                            cityList.add(citiesList.getString(k));
                            String cityName = citiesList.getString(k);

                            Map<Integer, String> cityHashmap = new HashMap<>();
                            cityHashmap.put(k, cityName);
                            stateHashMap.put(stateName, cityHashmap);

                            data.put(countryName, stateHashMap);

                        }
                    }
                }


            } catch (JSONException e) {
                e.printStackTrace();
            }