Parsing json response

Let’s look at how to parse JSON objects in android




Android JSON Support
    Android already contains the required JSON libraries. The Following class are used to parse the JSON Object.

    JSONArray          A JSONArray is an ordered sequence of values.
    JSONObject        A JSONObject is an unordered collection of name/value pairs.
    JSONStringer     JSONStringer provides a quick and convenient way of producing JSON text.
    JSONTokener     A JSONTokener takes a source string and extracts characters and tokens from it.


Steps to Parse JSON data
1. Create a JSON Object and Convert JSONString to JSON Object
    JSONObject jObject = new JSONObject(jsonString);
   
2. Create a Key based JSONObject.
    JSONObject menuObject = jObject.getJSONObject("menu");

3. Get the Value
    Log.d("ID", menuObject.getString("id"));
    Log.d("Value ", menuObject.getString("value"));
 
1> First we’ll need an example :
Lets look at a standard example from the json site http://json.org/example.html

{"menu": {
  "id": "file",
  "value": "File",
  "popup": {
    "menuitem": [
      {"value": "New", "onclick": "CreateNewDoc()"},
      {"value": "Open", "onclick": "OpenDoc()"},
      {"value": "Close", "onclick": "CloseDoc()"}
    ]
  }
}}

you could either save this in a file or save it in a string…..like I’ve done
2> Android already contains the required JSON libraries
Lets create a JSON Object;

private JSONObject jObject;

and lets our example be a String ,
private String jString = "{\"menu\": {\"id\": \"file\", \"value\": \"File\", \"popup\": { \"menuitem\": [ {\"value\": \"New\", \"onclick\": \"CreateNewDoc()\"}, {\"value\": \"Open\", \"onclick\": \"OpenDoc()\"}, {\"value\": \"Close\", \"onclick\": \"CloseDoc()\"}]}}}";



now we have to convert jString to the jObject ,
jObject = new JSONObject(jString);


Now we have to start extracting the content from jObject ,
Lets extract the menu object by creating a new menu object,
JSONObject menuObject = jObject.getJSONObject("menu"); Now lets extract its atrtibutes ,
String attributeId = menuObject.getString("id"); String attributeValue = menuObject.getString("value"); JSONObject popupObject = menuObject.getJSONObject("popup");


since “popup” is not plainly a String lets extract it to an object ,
3> Now popup contains an array of “menuitem”
So, we’ll have to extract it to a JSONArray,
JSONArray menuitemArray = popupObject.getJSONArray("menuitem"); Since it contains 3 items lets put it in a for loop.
for (int i = 0; i < 3; i++) { System.out.println(menuitemArray.getJSONObject(i) .getString("value").toString()); System.out.println(menuitemArray.getJSONObject(i).getString( "onclick").toString()); }

Basically thats it , u should see the output in the DDMS

4> The full code is as below,

import org.json.JSONArray;
import org.json.JSONObject;
import android.app.Activity;
import android.os.Bundle;

public class JsonParser extends Activity {
 private JSONObject jObject;
 private String jString = "{\"menu\": {\"id\": \"file\", \"value\": \"File\", \"popup\": { \"menuitem\": [ {\"value\": \"New\",   \"onclick\": \"CreateNewDoc()\"}, {\"value\": \"Open\", \"onclick\": \"OpenDoc()\"}, {\"value\": \"Close\", \"onclick\": \"CloseDoc()\"}]}}}";

 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
  try {
   parse();
  } catch (Exception e) {
   e.printStackTrace();
  }
 }
 private void parse() throws Exception {
  jObject = new JSONObject(jString);

  JSONObject menuObject = jObject.getJSONObject("menu");
  String attributeId = menuObject.getString("id");
  System.out.println(attributeId);

  String attributeValue = menuObject.getString("value");
  System.out.println(attributeValue);

  JSONObject popupObject = menuObject.getJSONObject("popup");
  JSONArray menuitemArray = popupObject.getJSONArray("menuitem");

  for (int i = 0; i < 3; i++) {
   System.out.println(menuitemArray.getJSONObject(i)
     .getString("value").toString());
   System.out.println(menuitemArray.getJSONObject(i).getString(
     "onclick").toString());
  }
 }
}