Question

I am trying to load data from a JSON web service and display it in a List View, this is my first time to use JSON and I am still beginner, so any one please tell me what is the problem

package com.androidhive.jsonparsing;

import java.util.ArrayList;
import java.util.HashMap;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.ListActivity;
import android.os.Bundle;
import android.widget.ListAdapter;
import android.widget.SimpleAdapter;

public class AndroidJSONParsingActivity extends ListActivity {

    // url to make request
    private static String url = "my url";

    // JSON Node names
     String TAG_CONTACTS = "TAG_CONTACTS";
     String Id = "Id";
     String DoctorName = "DoctorName";
     String ImageName = "ImageName";


    // contacts JSONArray
    JSONArray Doctors = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // Hashmap for ListView
        ArrayList<HashMap<String, String>> contactList = new ArrayList<HashMap<String, String>>();

        // Creating JSON Parser instance
        JSONParser jParser = new JSONParser();

        // getting JSON string from URL
        JSONObject json = jParser.getJSONFromUrl(url);

        try {
            // Getting Array of Contacts
            Doctors = json.getJSONArray(TAG_CONTACTS);

            // looping through All Contacts
            for(int i = 0; i < Doctors.length(); i++){
                JSONObject c = Doctors.getJSONObject(i);

                // Storing each json item in variable
//               String Id =  c.getString("Id");
//               String DoctorName =  c.getString("DoctorName");
//               String ImageName =  c.getString("ImageName");
//          

                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();

                // adding each child node to HashMap key => value
                map.put("Id", c.getString("Id"));
                map.put("DoctorName", c.getString("DoctorName"));
                map.put("ImageName", c.getString("ImageName"));

                // adding HashList to ArrayList
                contactList.add(map);
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }


        /**
         * Updating parsed JSON data into ListView
         * */
        ListAdapter adapter = new SimpleAdapter(this, contactList,
                R.layout.list_item,
                new String[] { DoctorName, ImageName }, new int[] {
                        R.id.name, R.id.image });

        setListAdapter(adapter);


    }

}

---

package com.androidhive.jsonparsing;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;

import android.util.Log;

public class JSONParser {

    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";

    // constructor
    public JSONParser() {

    }

    public JSONObject getJSONFromUrl(String url) {

        // Making HTTP request
        try {
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();           

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            is.close();
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // try parse the string to a JSON object
        try {
            jObj = new JSONObject(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // return JSON String
        return jObj;

    }
}

when i run it , it gives me this warning

12-13 12:41:57.052: W/System.err(542): org.json.JSONException: No value for TAG_CONTACTS
12-13 12:41:57.052: W/System.err(542):  at org.json.JSONObject.get(JSONObject.java:354)
12-13 12:41:57.052: W/System.err(542):  at org.json.JSONObject.getJSONArray(JSONObject.java:544)
12-13 12:41:57.052: W/System.err(542):  at com.androidhive.jsonparsing.AndroidJSONParsingActivity.onCreate(AndroidJSONParsingActivity.java:56)
12-13 12:41:57.063: W/System.err(542):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
12-13 12:41:57.063: W/System.err(542):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
12-13 12:41:57.063: W/System.err(542):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
12-13 12:41:57.063: W/System.err(542):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
12-13 12:41:57.063: W/System.err(542):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
12-13 12:41:57.063: W/System.err(542):  at android.os.Handler.dispatchMessage(Handler.java:99)
12-13 12:41:57.072: W/System.err(542):  at android.os.Looper.loop(Looper.java:123)
12-13 12:41:57.072: W/System.err(542):  at android.app.ActivityThread.main(ActivityThread.java:3683)
12-13 12:41:57.072: W/System.err(542):  at java.lang.reflect.Method.invokeNative(Native Method)
12-13 12:41:57.072: W/System.err(542):  at java.lang.reflect.Method.invoke(Method.java:507)
12-13 12:41:57.072: W/System.err(542):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)

and it opens an empty screen ! what is the problem ?

Answer 1

You are passing a wrong name for the JSON Array.. org.json.JSONException: No value for TAG_CONTACTS
it should be:

// Getting Array of Contacts
Doctors = json.getJSONArray("Doctors");