Sending and Parsing JSON in Android

Question

In the application I am developing, I would like to send messages in the form of JSON objects to a Django Server and parse the JSON response from the server and populate a custom listview.

From the little JSON knowledge I have, I thought this format for the response from server

{
  "post": {
    "username": "someusername",
    "message": "this is a sweet message",
    "image": "http://localhost/someimage.jpg",
    "time":  "present time"
  },
}

How much knowledge of JSON should I have to accomplish this purpose? Also it would be great if someone could provide me links of some tutorials for sending and parsing JSON Objects.

Edit: Is there any advantage using GSON Parser rather than 'get' command for parsing JSON responses?

Answer 1

You can download a library from http://json.org (Json-lib or org.json) and use it to parse/generate the JSON

Answer 2

There's not really anything to JSON. Curly brackets are for "objects" (associative arrays) and square brackets are for arrays without keys (numerically indexed). As far as working with it in Android, there are ready made classes for that included in the sdk (no download required).

Check out these classes: http://developer.android.com/reference/org/json/package-summary.html

Answer 3

You can use org.json.JSONObject and org.json.JSONTokener. you don't need any external libraries since these classes come with Android SDK

Answer 4

I am surprised these have not been mentioned: but instead of using bare-bones rather manual process with json.org's little package, GSon and Jackson are much more convenient to use. So:

• GSON
• Jackson

So you can actually bind to your own POJOs, not some half-assed tree nodes or Lists and Maps. (and at least Jackson allows binding to such things too (perhaps GSON as well, not sure), JsonNode, Map, List, if you really want these instead of 'real' objects)

Answer 5

GSON is easiest to use and the way to go if the data have a definite structure.

Download gson.

Add it to the referenced libraries.

package com.tut.JSON;

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

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

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

public class SimpleJson extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        String jString = "{\"username\": \"primal\", \"message\": \"Hi, I am Primal\"}  ";


        GsonBuilder gsonb = new GsonBuilder();
        Gson gson = gsonb.create();
        Post pst = null;

        try {
            JSONObject j =new JSONObject(jString);
            pst = gson.fromJson(j.toString(),  Post.class);

        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        Log.d("TAggeD", pst.username + pst.message);

        Log.d("TAGGED", gson.toJson(pst));


    }
}

Code for Post class

package com.tut.JSON;

import android.graphics.Bitmap;

public class Post {

    String message;
    String time;
    String username;
    Bitmap icon;

    public String getMessage(){
        return message;
    }

    public String getUsername(){
        return username;
    }

    public Bitmap getIcon(){
        return icon;
    }

    public void setUsername(String un){
        this.username = un;
    }

    public void setMessage(String msg){
        this.message = msg;
    }

    public void setIcon(Bitmap icon){
        this.icon = icon;
    }
}

Hope it helps.

Answer 6

I have a tutorial on my site that I think goes pretty in depth about using Android to parse JSON. It might be able to help you out... I use the code in it in my own application (which parses JSON responses from a webserver).