JSON example in Android

1.1. Android and JSON

JSON is a very condense data exchange format. Android includes the json.org libraries which allow to work easily with JSON files.

1.2. Twitter

Twitter is a great source for JSON. You can just call a URI and retrieve JSON. Here are some examples:

Table 1. Twitter URI's

URI	Description
http://twitter.com/statuses/user_timeline/vogella.json	Get the timeline of user vogella .
http://search.twitter.com/search.json?q=android	Search for the term "android" on Twitter.
http://twitter.com/statuses/user_timeline/vogella.json	Returns the user data of user vogella .

Please note that some URI's return a JSONObject object while others return a JSONArray. The following coding uses an URI which returns an JSONArray.

2. Reading JSON

Create a new Android project "de.vogella.android.twitter.json" with the package "de.vogella.android.twitter.json" and the activity "ParseJSON".
Create the following coding for the activity. This will download the twitter feed for the userhttp://twitter.com/vogella and write the number of entries and the text messages to the Android log file.

   
package de.vogella.android.twitter.json;

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

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.StatusLine;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONObject;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

public class ParseJSON extends Activity {
 

/** Called when the activity is first created. */
@Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
  String readTwitterFeed = readTwitterFeed();
  try {
   JSONArray jsonArray = new JSONArray(readTwitterFeed);
   Log.i(ParseJSON.class.getName(),
     "Number of entries " + jsonArray.length());
   for (int i = 0; i < jsonArray.length(); i++) {
    JSONObject jsonObject = jsonArray.getJSONObject(i);
    Log.i(ParseJSON.class.getName(), jsonObject.getString("text"));
   }
  } catch (Exception e) {
   e.printStackTrace();
  }
 }

 public String readTwitterFeed() {
  StringBuilder builder = new StringBuilder();
  HttpClient client = new DefaultHttpClient();
  HttpGet httpGet = new HttpGet(
    "http://twitter.com/statuses/user_timeline/vogella.json");
  try {
   HttpResponse response = client.execute(httpGet);
   StatusLine statusLine = response.getStatusLine();
   int statusCode = statusLine.getStatusCode();
   if (statusCode == 200) {
    HttpEntity entity = response.getEntity();
    InputStream content = entity.getContent();
    BufferedReader reader = new BufferedReader(
      new InputStreamReader(content));
    String line;
    while ((line = reader.readLine()) != null) {
     builder.append(line);
    }
   } else {
    Log.e(ParseJSON.class.toString(), "Failed to download file");
   }
  } catch (ClientProtocolException e) {
   e.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  }
  return builder.toString();
 }
}
  

To run this example assign the uses-permission to your "AndroidManifest.xml" for "android.permission.INTERNET".

3. Write JSON

Writing JSON is very simple. Just create the JSONObject or JSONArray and use the toString() method.

    
public void writeJSON() {
 JSONObject object = new JSONObject();
 try {
  object.put("name", "Jack Hack");
  object.put("score", new Integer(200));
  object.put("current", new Double(152.32));
  object.put("nickname", "Hacker");
 } catch (JSONException e) {
  e.printStackTrace();
 }
 System.out.println(object);
}

More information about this articles. click Here.

Other resources related to JSON...

1.http://coderzheaven.com/2011/06/parsing-json-objects-in-android/

2.http://stackoverflow.com/questions/2818697/sending-and-parsing-json-in-android

3.http://code.google.com/p/google-gson/

4.http://developer.android.com/reference/org/json/JSONTokener.html

5.http://www.javabeat.net/articles/325-androids-json-parser-1.html

7.http://inchoo.net/mobile-development/android-development/simple-android-json-parsing-example-with-output-into-listactivity/