如何使用Volley解析JSON请求？

Question

I am using the Volley Facebook library to parse the JSON object by passing the String Parameter. But it's throwing JSON exception.

[  
   {  
      "error":false,
      "newsletter":[  
         {  
            "title":"IPS Informa",
            "date":"2015-12-02",
            "posted_by":"admin",
            "image":"1449324052220174144.png",
            "description":"Hello World",
            "id":"4",
            "post_count":"0"
         },
         {  
            "title":"IPS Informa",
            "date":"2015-11-30",
            "posted_by":"admin",
            "image":"1449324052220174144.png",
            "description":"Hello Worl Two",
            "id":"1",
            "post_count":"6"
         }
      ]
   }
]

And here is My Android Code to parse my JSON request:

StringRequest strReq = new StringRequest(Request.Method.POST,
                        url, new Response.Listener<String>() {
         @Override
            public void onResponse(String response) {

                    hidePDialog();

                    try {

                        JSONObject first = new JSONObject(response);
                        String err = first.getString("error");


                        JSONArray second = first.getJSONArray("newsletter");
                        fisco_tips.clear();
                        // Parsing json
                        for (int i = 0; i < second.length(); i++) {

                            JSONObject obj = second.getJSONObject(i);

                            FisoTipsSinglton fisco_obj = new FisoTipsSinglton();

                            //Set Newsletter ID
                            fisco_obj.setFisco_id(obj.getString("id"));
                            //Set Title
                            fisco_obj.setTitle(obj.getString("title"));
                            //Set Posted Date
                            fisco_obj.setPosted_date(obj.getString("date"));

                            //Set Posted By
                            fisco_obj.setPosted_by(obj.getString("posted_by"));
                            //Set Image URL
                            fisco_obj.setThumbnailUrl(obj.getString("image"));
                            //Set Short Description
                            fisco_obj.setShort_description(obj.getString("description"));
                            fisco_obj.setPost_count(obj.getString("post_count"));

                            fisco_tips.add(fisco_obj);


                        }

                    } catch (JSONException e) {
                        e.printStackTrace();
                        Log.d("Json Error", "Here is error: " + e.toString());

                    }
                     adapter.notifyDataSetChanged();
                }
            },
                new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
                hidePDialog();

            }
        }) {
            @Override
            protected Map<String, String> getParams() {
            // Posting params to register url
             Map<String, String> params = new HashMap<String, String>();

                        params.put("country", country);
                        return params;
                    }

                };
         AppController.getInstance().addToRequestQueue(strReq, related_posts);
    }

How can I read my JSON object using string request in Android Volley library?

Answer 1

The error message that you're getting:

type org.json.JSONArray cannot be converted to JSONObject

indicates that you're trying to convert a JSONArray to a JSONObject . This happens in the first line of code in your try block.

JSONObject first = new JSONObject(response);

You're passing the entire response to the JSONObject constructor, but the response is wrapped in [ ] , so it's a JSONArray , not a JSONObject . Your first step should be to parse the response as a JSONArray , get the JSONObject from the first element of the array, then continue parsing.

try {

    JSONArray wrapper = new JSONArray(response);

    JSONObject first = (JSONObject)wrapper.get(0);

    boolean err = first.getBoolean("error");

    JSONArray newsletters = first.getJSONArray("newsletter");

    // Parsing json
    for (int i = 0; i < newsletters.length(); i++) {
        JSONObject news = newsletters.getJSONObject(i);
        .
        .
        .
    }
} catch (JSONException e) {
    Log.d("MainActivity.java", e.toString());
}

If there's a chance that your data source might return an empty array, you should do more error checking than I've shown here.

Answer 2

String err = first.getString("error");

Should be:

Boolean err = first.getBoolean("error");

Plus what Bill the Lizard said.

Answer 3

Instead of using Volley check OkHTTP with Retrofit. It will wrap responses automatically ;)