Saturday, August 27, 2011

JSON Parsing in Android

1. Android and JSON

1.1. Android and JSON

JSON is a very condense data exchange format. Android includes the 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
URIDescription Get the timeline of user vogella . Search for the term "android" on Twitter. 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 "" with the package "" and the activity "ParseJSON".
Create the following coding for the activity. This will download the twitter feed for the user and write the number of entries and the text messages to the Android log file.



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

public class ParseJSON extends Activity {
	/** Called when the activity is first created. */
	public void onCreate(Bundle savedInstanceState) {
		String readTwitterFeed = readTwitterFeed();
	try {
		JSONArray jsonArray = new JSONArray(readTwitterFeed);
			"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) {

	public String readTwitterFeed() {
	StringBuilder builder = new StringBuilder();
	HttpClient client = new DefaultHttpClient();
	HttpGet httpGet = new HttpGet(
	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) {
		} else {
		Log.e(ParseJSON.class.toString(), "Failed to download file");
	} catch (ClientProtocolException e) {
	} catch (IOException e) {
	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) {

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