Android JSON Parser Example

Today I'll show you the Android code I used to parse a JSON string from a URL. This code is really useful because nowadays, JSON string is being used by most APIs like Facebook graph API and Google Maps.

DOWNLOAD CODE

You should use JSON in your projects instead of XML because it is lightweight, so much easier to parse, and is supported by most programming language. Recently I wrote about how to generate JSON string with PHP which can be useful for you too.

But if you really have to use XML, you can also take a look at my older post: Parse XML in Android With Three Input Sources

Contents:

1.0 Creating JSON String

2.0 Creating our JSON Parser Class

3.0 Using JSON Parser Class with JSON String

1.0 Creating JSON String

Create a JSON string and make it accessible via URL. I created an example for this post, you can see it in this URL: http://demo.codeofaninja.com/tutorials/json-example-with-php/index.php

What it looks like in a JSON viewer:

As for the code on how to create that JSON string, you can take a look at my older post: Generating JSON String with PHP

2.0 Create our JSON Parser Class

You can use this JSON parser class with any of your JSON string from URL. Here's our JsonParser.java:

package com.example.androidjsonparsing;

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 {

    final String TAG = "JsonParser.java";
    
    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";

    public JSONObject getJSONFromUrl(String url) {

        // make HTTP request
        try {

            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(TAG, "Error converting result " + e.toString());
        }

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

        // return JSON String
        return jObj;
    }
}

3.0 Using JSON Parser Class with JSON String

Now we want to make use of our JSON parser with the generated JSON string from URL. But before running our code, make sure you enable internet permission in your AndroidManifest.xml

<uses-permission android:name="android.permission.INTERNET"></uses-permission>

Now take a look at our MainActivity.java:

package com.example.androidjsonparsing;

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

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

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // we will using AsyncTask during parsing 
        new AsyncTaskParseJson().execute();
    }

    // you can make this class as another java file so it will be separated from your main activity.
    public class AsyncTaskParseJson extends AsyncTask<String, String, String> {

        final String TAG = "AsyncTaskParseJson.java";
        
        // set your json string url here
        String yourJsonStringUrl = "http://demo.codeofaninja.com/tutorials/json-example-with-php/index.php";

        // contacts JSONArray
        JSONArray dataJsonArr = null;

        @Override
        protected void onPreExecute() {}

        @Override
        protected String doInBackground(String... arg0) {

            try {

                // instantiate our json parser
                JsonParser jParser = new JsonParser();

                // get json string from url
                JSONObject json = jParser.getJSONFromUrl(yourJsonStringUrl);

                // get the array of users
                dataJsonArr = json.getJSONArray("Users");

                // loop through all users
                for (int i = 0; i < dataJsonArr.length(); i++) {
                    
                    JSONObject c = dataJsonArr.getJSONObject(i);

                    // Storing each json item in variable
                    String firstname = c.getString("firstname");
                    String lastname = c.getString("lastname");
                    String username = c.getString("username");

                    // show the values in our logcat
                    Log.e(TAG, "firstname: " + firstname 
                            + ", lastname: " + lastname
                            + ", username: " + username);

                }

            } catch (JSONException e) {
                e.printStackTrace();
            }

            return null;
        }

        @Override
        protected void onPostExecute(String strFromDoInBg) {}
    }
}

Logcat output looks like this:




Thanks for reading this Android JSON parsing tutorial!

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