Android Competency Center

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

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());
		}
	}
}

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