Android JSON Parsing Tutorial

http://www.androidhive.info/2012/01/android-json-parsing-tutorial/

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 explainedparsing 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":"[e-mail]",

                "address":"xx-xx-xxxx,x - street, x - country",

                "gender": "male",

                "phone": {

                    "mobile":"[phone]",

                    "home":"00 000000",

                    "office":"00 000000"

                }

        },

        {

                "id":"c201",

                "name":"Johnny Depp",

                "email":"[e-mail]",

                "address":"xx-xx-xxxx,x - street, x - country",

                "gender": "male",

                "phone": {

                    "mobile":"[phone]",

                    "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 anJSONArray node whereas curly bracket represents JSONObject. 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.

JSONParser.java

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 {

 

    staticInputStream is = null;

    staticJSONObject jObj = null;

    staticString json = "";

 

    // constructor

    publicJSONParser() {

 

    }

 

    publicJSONObject 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(newInputStreamReader(

                    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

        returnjObj;

 

    }

}

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.

// url to make request

private static String url = "http://api.androidhive.info/contacts/";

 

// 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";

privatestatic final String TAG_PHONE = "phone";

privatestatic final String TAG_PHONE_MOBILE = "mobile";

privatestatic final String TAG_PHONE_HOME = "home";

privatestatic final String TAG_PHONE_OFFICE = "office";

 

// contacts JSONArray

JSONArray 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 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(inti = 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.

AndroidJSONParsingActivity.java

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 extendsListActivity {

 

    // url to make request

    privatestatic String url = "http://api.androidhive.info/contacts/";

 

    // JSON Node names

    privatestatic final String TAG_CONTACTS = "contacts";

    privatestatic final String TAG_ID = "id";

    privatestatic final String TAG_NAME = "name";

    privatestatic final String TAG_EMAIL = "email";

    privatestatic final String TAG_ADDRESS = "address";

    privatestatic final String TAG_GENDER = "gender";

    privatestatic final String TAG_PHONE = "phone";

    privatestatic final String TAG_PHONE_MOBILE = "mobile";

    privatestatic final String TAG_PHONE_HOME = "home";

    privatestatic final String TAG_PHONE_OFFICE = "office";

 

    // contacts JSONArray

    JSONArray contacts =null;

 

    @Override

    publicvoid 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(inti = 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,

                newString[] { 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(newOnItemClickListener() {

 

            @Override

            publicvoid onItemClick(AdapterView<?> parent, View view,

                    intposition, 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);

            }

        });

    }

 

}