how to fetch json object from url in android

Question

I want to fetch json data from json object. My json data is:{"avg":2.5} and my android code is

public class AsyncTaskParseJson extends AsyncTask < String, String, String > {

        final String TAG = "AsyncTaskParseJson.java";

        // set your json string url here
        String yourJsonStringUrl = "http://www.bsservicess.com/photoUpload/star_avg.php?bookName=" + book_name;

        // contacts JSONArray

        @Override
        protected void onPreExecute() {}

        @Override
        protected String doInBackground(String...arg0) {

            try {
                JSONParser jParser = new JSONParser();

                // get json string from url
                JSONObject json = jParser.getJSONFromUrl(yourJsonStringUrl);

                // get the array of users
                JSONObject dataJsonArr = json.getJSONObject(str);

                String c = dataJsonArr.getString("avg");
                na = c;
                starts = Float.parseFloat(c);


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

            return null;
        }

        @Override
        protected void onPostExecute(String strFromDoInBg) {
            super.onPostExecute(strFromDoInBg);

            netRate.setRating(starts);
            Toast.makeText(mybookview.this, Float.toString(starts), Toast.LENGTH_SHORT).show();
        }

But somehow its not working.I have trie every tutorial and evrything but nothing works.plz help me

Could you please explain which part doesn' work? Did you tried to enter in debug mode and see what happen in every step? Opening the link you can see a warning in your back end Warning: `Division by zero in /home/mohanmanali9/public_html/photoUpload/star_avg.php on line 30` — michoprogrammer, Jul 14 '16 at 07:12
actually i dont konw how to fetch data fron json object.I just want to know the method to fetch the data fron json object — Nicky Manali, Jul 14 '16 at 07:14
First of all you need a model class for mapping your json, then the procedure that you follow is almost correct. [here](http://stackoverflow.com/a/38337023/1222099) you can find a good explanation. — michoprogrammer, Jul 14 '16 at 07:19
1) [Get your string from the server](https://developer.android.com/training/volley/simple.html) 2) [Parse the JSON](http://stackoverflow.com/questions/2591098/how-to-parse-json-in-java) assuming that you are actually getting JSON from the URL — OneCricketeer, Jul 14 '16 at 07:31
try using retrofit2, you will never bother to think about asynchronous or json parsing anymore :) — Faruk, Jul 14 '16 at 07:43

score 0 · Answer 1 · edited May 23 '17 at 10:28

0

this is for simple get data from url example:

Parse JSON from HttpURLConnection object

and if you want use library then try Volley: tutorial link:

http://www.androidhive.info/2014/05/android-working-with-volley-library-1/

edited May 23 '17 at 10:28

Community

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answered Jul 14 '16 at 07:12

Jaydeep Devda

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what is your actual problem jsonparsing or get jsondata from url? – Jaydeep Devda Jul 14 '16 at 07:23
there is plenty of good network library you can use. like Volley http://www.androidhive.info/2014/05/android-working-with-volley-library-1/ – Jaydeep Devda Jul 14 '16 at 07:40

score 0 · Answer 2 · edited Jul 14 '16 at 07:26

0

your getting the json data in response is as {"avg":2.5} simple remove the below code

 JSONObject dataJsonArr = json.getJSONObject(str);

 String c = dataJsonArr.getString("avg");

with below line

String c = json.getString("avg");

edited Jul 14 '16 at 07:26

OneCricketeer

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answered Jul 14 '16 at 07:20

user3953005

1
1

srry but it giving me an error: Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String org.json.JSONObject.getString(java.lang.String)' on a null object reference – Nicky Manali Jul 14 '16 at 07:40

michoprogrammer · Answer 3 · 2016-07-14T07:52:11.063

0

A very simple solution to your problem

String str = "{ \"avg\" :0 }";
JsonParser parser = new JsonParser();
JsonObject object = (JsonObject) parser.parse(str);
String value = object.get("avg").getAsString();

But first of all you have to correct the warning in your backend.

EDIT the complete solution

public class AsyncTaskParseJson extends AsyncTask < String, String, String > {

    HttpURLConnection urlConnection;

    @Override
    protected String doInBackground(String...args) {

        StringBuilder result = new StringBuilder();

        try {
            URL url = new URL("http://www.bsservicess.com/photoUpload/star_avg.php?bookName=" + book_name);
            urlConnection = (HttpURLConnection) url.openConnection();
            InputStream in = new BufferedInputStream(urlConnection.getInputStream());

            BufferedReader reader = new BufferedReader(new InputStreamReader( in ));

            String line;
            while ((line = reader.readLine()) != null) {
                result.append(line);
            }

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            urlConnection.disconnect();
        }

        return result.toString();
    }

    @Override
    protected void onPostExecute(String result) {
        JsonParser parser = new JsonParser();
        JsonObject object = (JsonObject) parser.parse(result);
        String value = object.get("avg").getAsString();
    }

}

But first of all remove the warning from the web response!

edited Jul 14 '16 at 07:52

answered Jul 14 '16 at 07:26

michoprogrammer

1,159
2
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That's not getting the json from a web request – OneCricketeer Jul 14 '16 at 07:27
@cricket_007 the problem of Nicky is not about getting the data from a web request, because the logic of the asynctask is correct, the problem is in parsing the data. So this solution fits perfect in his needs. – michoprogrammer Jul 14 '16 at 07:28
How do you know the logic is correct without seeing the response or the implementation of `jParser.getJSONFromUrl(yourJsonStringUrl);`? – OneCricketeer Jul 14 '16 at 07:32
The logic of the asynctask is correct, the parsing phase is wrong. How do you know this? Because I tried to open the url by myself with the same code and I fixed it before posting the solution. And I decided to post only the json part because the rest it works properly. Of course Nicky has to change the "str" that I have hard coded for the sake of simplicity. – michoprogrammer Jul 14 '16 at 07:36
but in this way im not using url so how did i get json object – Nicky Manali Jul 14 '16 at 07:43
JSONObject object = (JSONObject ) parser.parse(result); cannot resolve the method parser.parse(result) what should i do now – Nicky Manali Jul 14 '16 at 07:58
Did you import the gson library? Because I test the code that I wrote for you and it works properly. – michoprogrammer Jul 14 '16 at 08:12
Use: JSONObject response = new JSONObject(result); String m = response.optString("avg"); Inside your onPostExecute method instead of JsonParser – Ravi Rawal Jul 14 '16 at 08:39

how to fetch json object from url in android

3 Answers3