How to download JSON data in android

Question

I am developing an android application in which first I am sending request to Web service and getting the response status in 0 or 1 format if I get the response as 1 then complete JSON file is loaded. My question is I want to make an offline app for which I want to download the JSON data from one activity and read that data in different activity with listview displaying title of every downloaded JSON file. After clicking the listview item, JSON data is displayed. And some of the JSON data items contains URL of images I also want to download them and display them in another activity. I also want to encrypt the downloaded JSON data. Please Help me.

For reference I have attached the JSON file format.

{"test_time":7200,"time_taken":"0","time_left":"7200","score":null,"easy_score":null,"medium_score":null,"hard_score":null,"status":"n","sections":[{"section_id":"196498","section_name":"Reasoning Aptitude","section_no":1,"total_questions":"40","total_minutes":"24","questions":[{"question_id":"61562","question":{"1":{"text":"In a certain code GRANT is written as UOBSH and PRIDE is written as FEJSQ. How is SOLD written in that code?","image":"","imgHeight":"","imgWidth":""}},"correct_ans":{"1":{"text":"EMPT","image":"","imgHeight":"","imgWidth":""}},"rightOption":[],"rightOptionID":"246408","rightOptionNo":"2","anwer_explaination":{"1":{"text":"","image":"http://abc.com/testengine/images/questions/bankpower/image1.Jpeg","imgHeight":304,"imgWidth":212},"2":{"text":" ","image":"","imgHeight":"","imgWidth":""}},"question_time_taken":"10","marked":"0","skipped":"0","answer_id":"1395795","option_choose":"246407","question_status":1,"options":[{"OptionId":"246406","OptionDesc":{"1":{"text":"EPMT","image":"","imgHeight":"","imgWidth":""}}},{"OptionId":"246407","OptionDesc":{"1":{"text":"TPME","image":"","imgHeight":"","imgWidth":""}}},{"OptionId":"246408","OptionDesc":{"1":{"text":"EMPT","image":"","imgHeight":"","imgWidth":""}}},{"OptionId":"246409","OptionDesc":{"1":{"text":"CKNR","image":"","imgHeight":"","imgWidth":""}}},{"OptionId":"246410","OptionDesc":{"1":{"text":"ETPM","image":"","imgHeight":"","imgWidth":""}}}]},{"question_id":"61563","question":{"1":{"text":"Four of the following five are alike in a certain way and so form a group. Which is the one that does not belong to that group?","image":"","imgHeight":"","imgWidth":""}},"correct_ans":{"1":{"text":"27","image":"","imgHeight":"","imgWidth":""}},"rightOption":[],"rightOptionID":"246414","rightOptionNo":"3","anwer_explaination":{"1":{"text":"Mouse is odd rest are use for storage.","image":"","imgHeight":"","imgWidth":""}},"question_time_taken":"0","marked":"0","skipped":"1","answer_id":"","option_choose":"","question_status":3,"options":[{"OptionId":"246411","OptionDesc":{"1":{"text":"19","image":"","imgHeight":"","imgWidth":""}}},{"OptionId":"246412","OptionDesc":{"1":{"text":"17","image":"","imgHeight":"","imgWidth":""}}},{"OptionId":"246413","OptionDesc":{"1":{"text":"13","image":"","imgHeight":"","imgWidth":""}}},{"OptionId":"246414","OptionDesc":{"1":{"text":"27","image":"","imgHeight":"","imgWidth":""}}},{"OptionId":"246415","OptionDesc":{"1":{"text":"37","image":"","imgHeight":"","imgWidth":""}}}]}

Answer 1

parse all the data using the parser detailed in that link

http://www.androidhive.info/2012/01/android-json-parsing-tutorial/ then Write all the data into a file using the method below , this way ur data is downloaded and saved as a file

public void appendData(String text)
{       
    File myFile = new File("sdcard/myfile.file");
    if (!myFile.exists())
    {
      try
      {
          myFile.createNewFile();
      } 
      catch (IOException e)
      {
          // TODO Auto-generated catch block
          e.printStackTrace();
      }
  }
  try
  {
      //BufferedWriter for performance, true to set append to file flag
      BufferedWriter buf = new BufferedWriter(new FileWriter(myFile, true)); 
      buf.append(text);
      buf.newLine();
      buf.close();
  }
  catch (IOException e)
  {
      // TODO Auto-generated catch block
      e.printStackTrace();
  }
}

Answer 2

try {

                  DefaultHttpClient httpclient = new DefaultHttpClient();
        HttpPost httpPostRequest = new HttpPost(URL);


        // Set HTTP parameters
        /*StringEntity se;
        se = new StringEntity(jsonObjSend.toString());*/
        jsonObjSend.length();

        List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(jsonObjSend.length());
        nameValuePairs.add(new BasicNameValuePair("data", jsonObjSend.toString()));
       // Log.i("jsonObjSend.toString()","jsonObjSend.toString()"+jsonObjSend.toString());

        Log.i("HTTPPOST","URL: "+URL);
        Log.i("HTTPPOST","Request: "+jsonObjSend.toString());
        UrlEncodedFormEntity en=new UrlEncodedFormEntity(nameValuePairs);
        en.getContent();
        httpPostRequest.getParams().setParameter("http.socket.timeout", new Integer(600000));
        httpPostRequest.setEntity(en);
        long t = System.currentTimeMillis();
        HttpResponse response = (HttpResponse) httpclient.execute(httpPostRequest);
        Log.i(TAG, "HTTPResponse received in [" + (System.currentTimeMillis()-t) + "ms]");
        Log.i(TAG, httpPostRequest.getRequestLine().getProtocolVersion().toString());
        responses = convertEntityToString(response.getEntity(), "UTF-8");
        Log.i("HTTPPOST","Responce: "+responses);
        Log.i("HTTPPOST","******************");
        //Log.i("Encoding",response.getEntity().getContentEncoding().getName());



                if (response.equalsIgnoreCase("")) {
                    webresponse = 1;
                } else {
                    webresponse = 0;
                }
            } catch (IOException e) {
                h.post(new Runnable() {

                    @Override
                    public void run() {
                        pd.dismiss();
                        AlertNullWebserviceResponce();

                    }
                });

                e.printStackTrace();
            }

Answer 3

You need to do something like this:

   private class PrepareMapTask extends AsyncTask<String, Integer, Boolean>
    {
        // Initialize with invalid value
        private int mPrepareResult = -1;
        private String mJsonString = null;

        protected Boolean doInBackground(String... urls)
        {
            mJsonString = downloadFileFromInternet(urls[0]);
            if(mJsonString == null /*|| mJsonString.isEmpty()*/)
                return false;

            JSONObject jObject = null;
            try {
                jObject = new JSONObject(mJsonString);
                JSONArray jsonImageArray = jObject.getJSONArray("imageTarget");
                JSONArray jsonUrlArray = jObject.getJSONArray("videoUrls");
                JSONArray jsonVideoOrUrlArray = jObject.getJSONArray("videoOrUrl");
                if (jsonImageArray == null || jsonUrlArray == null)
                    return false;
                for (int i = 0; i<jsonImageArray.length(); i++){ 
                    mapTargetUrl.put(jsonImageArray.get(i).toString(), jsonUrlArray.get(i).toString());
                    mVideoOrUrl.add(jsonVideoOrUrlArray.get(i).toString());
                }
            } catch (JSONException e) {
                e.printStackTrace();
                return false;
            }

            return true;
        }

        protected void onPostExecute(Boolean result)
        {
        }

        private String downloadFileFromInternet(String url)
        {
            if(url == null /*|| url.isEmpty() == true*/)
                new IllegalArgumentException("url is empty/null");
            StringBuilder sb = new StringBuilder();
            InputStream inStream = null;
            try
            {
                url = urlEncode(url);
                URL link = new URL(url);
                inStream = link.openStream();
                int i;
                int total = 0;
                byte[] buffer = new byte[8 * 1024];
                while((i=inStream.read(buffer)) != -1)
                {
                    if(total >= (1024 * 1024))
                    {
                        return "";
                    }
                    total += i;
                    sb.append(new String(buffer,0,i));
                }
            }catch(Exception e )
            {
                e.printStackTrace();
                return null;
            }catch(OutOfMemoryError e)
            {
                e.printStackTrace();
                return null;
            }
            return sb.toString();
        }

        private String urlEncode(String url)
        {
            if(url == null /*|| url.isEmpty() == true*/)
                return null;
            url = url.replace("[","");
            url = url.replace("]","");
            url = url.replaceAll(" ","%20");
            return url;
        }

    }

Take the data structures as per your json and modify the code.