Android JSON Parsing example

JSON is built on two structures:

• A collection of name/value pairs. In various languages, this is realized as an object, record, struct, dictionary, hash table, keyed list, or associative array.
• An ordered list of values. In most languages, this is realized as an array, vector, list, or sequence.

These are universal data structures. Virtually all modern programming languages support them in one form or another. It makes sense that a data format that is interchangeable with programming languages also be based on these structures.
In JSON, they take on these forms:
An object is an unordered set of name/value pairs. An object begins with { (left brace) and ends with } (right brace). Each name is followed by : (colon) and the name/value pairs are separated by , (comma).

An array is an ordered collection of values. An array begins with [ (left bracket) and ends with ] (right bracket). Values are separated by , (comma).

A value can be a string in double quotes, or a number, or true or false or null, or an object or an array. These structures can be nested.

A string is a sequence of zero or more Unicode characters, wrapped in double quotes, using backslash escapes. A character is represented as a single character string. A string is very much like a C or Java string.

A number is very much like a C or Java number, except that the octal and hexadecimal formats are not used.




Create a project with name AndroidJSONparser and have a mainactivity as given and with the given code

MainActivity .java


package com.jitesh.androidjsonparser;

import java.util.ArrayList;
import java.util.HashMap;

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.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
import android.widget.AdapterView.OnItemClickListener;

public class MainActivity extends ListActivity {
private Context context;
private static String url = "http://docs.blackberry.com/sampledata.json";

private static final String TAG_VTYPE = "vehicleType";
private static final String TAG_VCOLOR = "vehicleColor";
private static final String TAG_FUEL = "fuel";
private static final String TAG_TREAD = "treadType";
private static final String TAG_OPERATOR = "approvedOperators";
private static final String TAG_NAME = "name";
private static final String TAG_POINTS = "experiencePoints";

ArrayList<HashMap<String, String>> jsonlist = new ArrayList<HashMap<String, String>>();

ListView lv ;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new ProgressTask(MainActivity.this).execute();
}

private class ProgressTask extends AsyncTask<String, Void, Boolean> {
private ProgressDialog dialog;

public ProgressTask(ListActivity activity) {

Log.i("1", "Called");
context = activity;
dialog = new ProgressDialog(context);
}

/** progress dialog to show user that the backup is processing. */

/** application context. */
private Context context;

protected void onPreExecute() {
this.dialog.setMessage("Progress start");
this.dialog.show();
}

@Override
protected void onPostExecute(final Boolean success) {
if (dialog.isShowing()) {
dialog.dismiss();
}
ListAdapter adapter = new SimpleAdapter(context, jsonlist,
R.layout.list_item, new String[] { TAG_VTYPE, TAG_VCOLOR,
TAG_FUEL, TAG_TREAD }, new int[] {
R.id.vehicleType, R.id.vehicleColor, R.id.fuel,
R.id.treadType });

setListAdapter(adapter);

// selecting single ListView item
lv = getListView();






}

protected Boolean doInBackground(final String... args) {

JSONParser jParser = new JSONParser();

// getting JSON string from URL
JSONArray json = jParser.getJSONFromUrl(url);

for (int i = 0; i < json.length(); i++) {

try {
JSONObject c = json.getJSONObject(i);
String vtype = c.getString(TAG_VTYPE);

String vcolor = c.getString(TAG_VCOLOR);
String vfuel = c.getString(TAG_FUEL);
String vtread = c.getString(TAG_TREAD);

HashMap<String, String> map = new HashMap<String, String>();

// adding each child node to HashMap key => value
map.put(TAG_VTYPE, vtype);
map.put(TAG_VCOLOR, vcolor);
map.put(TAG_FUEL, vfuel);
map.put(TAG_TREAD, vtread);
jsonlist.add(map);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

return null;

}

}

}

JSONParser.java code is given below

package com.jitesh.androidjsonparser;

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.StatusLine;

import org.apache.http.client.ClientProtocolException;

import org.apache.http.client.HttpClient;

import org.apache.http.client.methods.HttpGet;

import org.apache.http.client.methods.HttpPost;

import org.apache.http.impl.client.DefaultHttpClient;

import org.json.JSONArray;

import org.json.JSONException;

import org.json.JSONObject;

import android.util.Log;

public class JSONParser {

static InputStream is = null;

static JSONArray jarray = null;

static String json = "";

// constructor

public JSONParser() {

}

public JSONArray getJSONFromUrl(String url) {

  StringBuilder builder = new StringBuilder();

   HttpClient client = new DefaultHttpClient();

   HttpGet httpGet = new HttpGet(url);

   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("==>", "Failed to download file");

     }

   } catch (ClientProtocolException e) {

     e.printStackTrace();

   } catch (IOException e) {

     e.printStackTrace();

   }

 

// try parse the string to a JSON object

try {

jarray = new JSONArray( builder.toString());

} catch (JSONException e) {

Log.e("JSON Parser", "Error parsing data " + e.toString());

}

// return JSON String

return jarray;

}

}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    android:orientation="vertical">

<!-- Main ListView 

Always give id value as list(@android:id/list)

-->

    <ListView

        android:id="@android:id/list"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"/>

</LinearLayout>

list_item.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="fill_parent"

    android:layout_height="wrap_content"

    android:orientation="horizontal">  

    <LinearLayout

        xmlns:android="http://schemas.android.com/apk/res/android"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:orientation="vertical">

<!-- Name Label -->

        <TextView

            android:id="@+id/vehicleType"

            android:layout_width="fill_parent"

            android:layout_height="wrap_content"

            android:textColor="#43bd00"

            android:textSize="16sp"

            android:textStyle="bold"

            android:paddingTop="6dip"

            android:paddingBottom="2dip" />

<!-- Description label -->

        <TextView

            android:id="@+id/vehicleColor"

            android:layout_width="fill_parent"

            android:layout_height="wrap_content"

            android:textColor="#acacac"

            android:paddingBottom="2dip">

        </TextView>

        

        <LinearLayout

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:orientation="horizontal">

        <!-- Cost Label -->

        <TextView

              android:id="@+id/fuel"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:textColor="#5d5d5d"

            android:gravity="left"

            android:textStyle="bold"

            android:text="Mobile: " >

        </TextView>

        <!-- Price Label -->

        <TextView

            android:id="@+id/treadType"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:textColor="#acacac" 

            android:textStyle="bold"

            android:gravity="left">

        </TextView>

        </LinearLayout>

    </LinearLayout>

</LinearLayout>

do not forget to add the internet permissions.

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

the output can be shown as follows

you can download the code from the given link JSONPARSER