Android - how to parse JsonArray from string?

Question

I am trying to parse a json array from json string but it always throws the exception data of type java.lang.String cannot be converted to JSONArray.

Please tell me if I make any mistake.

Thanks.

Here is my codes to get Json from server:

try {
                String url = String.format(<url here>, province.provinceCode2);
                HttpClient httpClient = getHttpClient();
                HttpGet httpGet = new HttpGet(url);
                HttpResponse httpResponse = httpClient.execute(httpGet);
                HttpEntity entity = httpResponse.getEntity();
                final String result = EntityUtils.toString(entity);
                parseAndSaveJsonData(province, result);
            } catch (Exception e) {
                e.printStackTrace();
            }

here is codes to parse JsonArray:

String jsonString = <below json string>
JSONArray ja = new JSONArray(jsonString);

Here is my json string:

   [
   {
      "LotPrizes":[
         {
            "Prize":"Giảitám",
            "Range":"50"
         },
         {
            "Prize":"Giảibảy",
            "Range":"264"
         },
         {
            "Prize":"Giảisáu",
            "Range":"3654-5162-3097"
         },
         {
            "Prize":"Giảinăm",
            "Range":"9739"
         },
         {
            "Prize":"Giảitư",
            "Range":"97690-99274-32442-69432-04855-10132-17085"
         },
         {
            "Prize":"Giảiba",
            "Range":"73745-13007"
         },
         {
            "Prize":"Giảinhì",
            "Range":"05521"
         },
         {
            "Prize":"Giảinhất",
            "Range":"74870"
         },
         {
            "Prize":"GiảiDB6",
            "Range":"878833"
         }
      ]
      },
 {
      "LotPrizes":[
         {
            "Prize":"Giảitám",
            "Range":"50"
         },
         {
            "Prize":"Giảibảy",
            "Range":"264"
         },
         {
            "Prize":"Giảisáu",
            "Range":"3654-5162-3097"
         },
         {
            "Prize":"Giảinăm",
            "Range":"9739"
         },
         {
            "Prize":"Giảitư",
            "Range":"97690-99274-32442-69432-04855-10132-17085"
         },
         {
            "Prize":"Giảiba",
            "Range":"73745-13007"
         },
         {
            "Prize":"Giảinhì",
            "Range":"05521"
         },
         {
            "Prize":"Giảinhất",
            "Range":"74870"
         },
         {
            "Prize":"GiảiDB6",
            "Range":"878833"
         }
      ]
      }

    ]

Answer 1

This is how to initialize a JSON parser:

JSONObject jsonObject = new JSONObject(jsonString);

That will give you the entire string as a Json Object. From there, pull out an individual array as a JsonArray, like this:

JSONArray jsonArray = jsonObject.getJSONArray("LotPrizes");

To access each "LotPrizes" you can use for loop logic:

for(int i=0;i<jsonArray.length();i++)
{
  JSONObject curr = jsonArray.getJSONObject(i);

  prize = curr.getString("Prize")

//Do stuff with the Prize String here
//Add it to a list, print it out, etc.
}

EDIT: Final code after your JSON edit:

JSONArray jsonArray = null;
String jsonString = <your string>
String currPrize = null;

JSONObject jsonObject = new JSONObject(jsonString);

jsonArray = jsonObject.getJSONArray("data");

for(int i=0;i<jsonArray.length();i++)
{
    JSONArray currLot = jsonArray.getJSONObject(i);

    for(int j=0; j<currLot.length();j++)
    {
        JSONobject curr = currLot.getJSONObject(j);

        currPrize = curr.getString("Prize");

        //Do something with Prize
    }
}

This code is functional and I'm using an almost identical version in my code. Hope this (finally) works for you.

Answer 2

Hi @Caerulius, Harish, ρяσѕρєя K, Hot Licks , and all. Finally, after 2 days of headache and 2 sleepless nights, I solved the issue. And because you spend your valued time to discuss with me, I see that I have to tell you the root cause. That's my responsibility.

First of all, I am a senior android developer. So, I at least know about JSON basic, I know how to parse data from JSON string, and I know many useful online tools to validate it. I confirm that the JSON string I got from server is valid.

As I told in my question, I used final String result = EntityUtils.toString(entity); to get JSON string from HttpEntity object. I have used this many times in the past and it worked. No problem. But, in this case, it's not. The original JSON string like this:

   [{
      "LotPrizes":[
         {
            "Prize":"Giảitám",
            "Range":"50"
         },
         {
            "Prize":"Giảibảy",
            "Range":"264"
         },
         ...
    }]

But what I got like this:

"[{
      \"LotPrizes\":[
         {
            \"Prize":\"Giảitám\",
            \"Range\":\"50\"
         },
         {
            \"Prize\":\"Giảibảy\",
            \"Range\":\"264\"
         },
         ...
    }]"

This string is similar with the constant string which we may declare as below:

String stringVariable = "\"[{
          \\\"LotPrizes\\\":[
             {
                \\\"Prize":\\\"Giảitám\\\",
                \\\"Range\\\":\\\"50\\\"
             },
             {
                \\\"Prize\\\":\\\"Giảibảy\\\",
                \\\"Range\\\":\\\"264\\\"
             },
             ...
        }]\" ;

It's a valid string, but not a valid JSON String.

To fix this issue, I change the way to get JSON string, and remove unnecessary characters like this:

                            HttpClient httpClient = getHttpClient();
                HttpGet httpGet = new HttpGet(url);
                HttpResponse httpResponse = httpClient.execute(httpGet);
                HttpEntity entity = httpResponse.getEntity();
                InputStream is = entity.getContent();
                BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"), 8);
                StringBuilder sb = new StringBuilder();
                String line = null;
                while ((line = reader.readLine()) != null) {
                    sb.append(line + "\n");
                }
                is.close();
                String json = sb.toString();

                json = json.replace("\\", "");
                json = json.substring(1);
                json = json.substring(0, json.length() - 2);

Now, the json variable contain JSON string which I can parse correctly. I think this should a bug of HttpEntity library.

Hope this helps some other guys.

Answer 3

You can retrieve the jsondata from your string as follows ..

            JSONObject json = new JSONObject(jsonString);
            JSONArray jData = json.getJSONArray("data");
            for (int i = 0; i < jData.length(); i++) {
                JSONObject jo = jData.getJSONObject(i);

                JSONArray jLotPrizes = jo.getJSONArray("LotPrizes");
                for (int j = 0; j < jLotPrizes.length(); j++) {
                    JSONObject jobj = jLotPrizes.getJSONObject(j);

                    Log.i("Prize", "" + jobj.getString("Prize"));
                    Log.i("Range", "" + jobj.getString("Range"));
                }

            }