JSON is the best alternative to XML for storing data in files. It is easy to parse and access data stored in JSON format. Previously i explained parsing XML and today i am going to discuess parsing JSON data with an example.
The JSON Structure
I am taking an example of following JSON which will give you list of contacts and each contact will have details like name, email, address, phone number ertc,. You can get this JSON data by accessinghttp://api.androidhive.info/contacts/
{ "contacts": [ { "id": "c200", "name": "Ravi Tamada", "email": "ravi@gmail.com", "address": "xx-xx-xxxx,x - street, x - country", "gender" : "male", "phone": { "mobile": "+91 0000000000", "home": "00 000000", "office": "00 000000" } }, { "id": "c201", "name": "Johnny Depp", "email": "johnny_depp@gmail.com", "address": "xx-xx-xxxx,x - street, x - country", "gender" : "male", "phone": { "mobile": "+91 0000000000", "home": "00 000000", "office": "00 000000" } }, . . . . ]} |
The difference between [ and { - (Square brackets and Curly brackets)
If you observe normally JSON data will have square brackets and curly brackets. The difference between [ and { is, the square bracket represents starting of an JSONArray node whereas curly bracket representsJSONObject. While accessing these elements we need to call different methods to access these nodes.
Writing JSON Parser Class
In your project create a class file and name it as JSONParser.java. The parser class has a method which will make http request to get JSON data and returns a JSONObject.
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; }} |
Parsing JSON Data
Once you created parser class next thing is to know how to use that class. Below i am explaining how to parse the json (taken in this example) using the parser class.
1. In the contacts json we have items like name, email, address, gender and phone numbers. So first thing is to store all these node names in variables. Open your main activity class and declare store all node names in static variables.
1. In the contacts json we have items like name, email, address, gender and phone numbers. So first thing is to store all these node names in variables. Open your main activity class and declare store all node names in static variables.
// url to make request// JSON Node namesprivate static final String TAG_CONTACTS = "contacts";private static final String TAG_ID = "id";private static final String TAG_NAME = "name";private static final String TAG_EMAIL = "email";private static final String TAG_ADDRESS = "address";private static final String TAG_GENDER = "gender";private static final String TAG_PHONE = "phone";private static final String TAG_PHONE_MOBILE = "mobile";private static final String TAG_PHONE_HOME = "home";private static final String TAG_PHONE_OFFICE = "office";// contacts JSONArrayJSONArray contacts = null; |
2. Next step to is to use parser class to get JSONObject and looping through each json item. Below i am creating an instance of JSONParser class and using for loop i am looping through each json item and finally storing each json data in variable.
// Creating JSON Parser instanceJSONParser jParser = new JSONParser();// getting JSON string from URLJSONObject json = jParser.getJSONFromUrl(url);try { // Getting Array of Contacts contacts = json.getJSONArray(TAG_CONTACTS); // looping through All Contacts for(int i = 0; i < contacts.length(); i++){ JSONObject c = contacts.getJSONObject(i); // Storing each json item in variable String id = c.getString(TAG_ID); String name = c.getString(TAG_NAME); String email = c.getString(TAG_EMAIL); String address = c.getString(TAG_ADDRESS); String gender = c.getString(TAG_GENDER); // Phone number is agin JSON Object JSONObject phone = c.getJSONObject(TAG_PHONE); String mobile = phone.getString(TAG_PHONE_MOBILE); String home = phone.getString(TAG_PHONE_HOME); String office = phone.getString(TAG_PHONE_OFFICE); }} catch (JSONException e) { e.printStackTrace();} |
Parsing JSON data and updating into ListView
In my previous tutorial Android ListView Tutorial i explained how to create listview and updating with list data. Below i am implementing same listview but the list data i am updating is from parsed JSON.
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.content.Intent;import android.os.Bundle;import android.util.Log;import android.view.View;import android.widget.AdapterView;import android.widget.AdapterView.OnItemClickListener;import android.widget.ListAdapter;import android.widget.ListView;import android.widget.SimpleAdapter;import android.widget.TextView;public class AndroidJSONParsingActivity extends ListActivity { // url to make request // JSON Node names private static final String TAG_CONTACTS = "contacts"; private static final String TAG_ID = "id"; private static final String TAG_NAME = "name"; private static final String TAG_EMAIL = "email"; private static final String TAG_ADDRESS = "address"; private static final String TAG_GENDER = "gender"; private static final String TAG_PHONE = "phone"; private static final String TAG_PHONE_MOBILE = "mobile"; private static final String TAG_PHONE_HOME = "home"; private static final String TAG_PHONE_OFFICE = "office"; // contacts JSONArray JSONArray contacts = 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 contacts = json.getJSONArray(TAG_CONTACTS); // looping through All Contacts for(int i = 0; i < contacts.length(); i++){ JSONObject c = contacts.getJSONObject(i); // Storing each json item in variable String id = c.getString(TAG_ID); String name = c.getString(TAG_NAME); String email = c.getString(TAG_EMAIL); String address = c.getString(TAG_ADDRESS); String gender = c.getString(TAG_GENDER); // Phone number is agin JSON Object JSONObject phone = c.getJSONObject(TAG_PHONE); String mobile = phone.getString(TAG_PHONE_MOBILE); String home = phone.getString(TAG_PHONE_HOME); String office = phone.getString(TAG_PHONE_OFFICE); // creating new HashMap HashMap<String, String> map = new HashMap<String, String>(); // adding each child node to HashMap key => value map.put(TAG_ID, id); map.put(TAG_NAME, name); map.put(TAG_EMAIL, email); map.put(TAG_PHONE_MOBILE, mobile); // 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[] { TAG_NAME, TAG_EMAIL, TAG_PHONE_MOBILE }, new int[] { R.id.name, R.id.email, R.id.mobile }); setListAdapter(adapter); // selecting single ListView item ListView lv = getListView(); // Launching new screen on Selecting Single ListItem lv.setOnItemClickListener(new OnItemClickListener() { @Override public void onItemClick(AdapterView<?> parent, View view, int position, long id) { // getting values from selected ListItem String name = ((TextView) view.findViewById(R.id.name)).getText().toString(); String cost = ((TextView) view.findViewById(R.id.email)).getText().toString(); String description = ((TextView) view.findViewById(R.id.mobile)).getText().toString(); // Starting new intent Intent in = new Intent(getApplicationContext(), SingleMenuItemActivity.class); in.putExtra(TAG_NAME, name); in.putExtra(TAG_EMAIL, cost); in.putExtra(TAG_PHONE_MOBILE, description); startActivity(in); } }); }} |
