Android Json Processing using GSON and Display in on a ListView

This is my way to process a json request using GSON library and display it on a ListView

Connect to a WebService

the code i used to interact with the web service is based on this blog http://lukencode.com/2010/04/27/calling-web-services-in-android-using-httpclient/

First, download GSON library in here

Format JSON Response

the json response format which we are going to response is like this:

{"locations":[{"name":"test","description":"testse","latlng":[12.0,13.0]},{"name":"gfd","description":"hh","latlng":[15.0,16.0]},{"name":"rumah bagas","description":"iki rumahe bagas","latlng":[0.0,20.0]}]}

the Model

in the json response show that it has a locations that consist on many location.

The LocationModel.java is the basic data from the json response:

package com.bopbi.model;

public class LocationModel {
	private String name;
	private String description;
	private float[] latlng;

	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getDescription() {
		return description;
	}
	public void setDescription(String description) {
		this.description = description;
	}

	public float[] getLatlng() {
		return latlng;
	}
	public void setLatlng(float[] latlng) {
		this.latlng = latlng;
	}
}

and the LocationList.java which the container for the LocationModel:

package com.bopbi.model;

import java.util.List;

public class LocationList {
    private List locations;

    public List getLocations() {
        return locations;
    }
    public void setLocationList(List locations) {
        this.locations = locations;
    }
}

LocationAdapter.java is the adapter that will be use to display the LocationList in a ListView is extends from an ArrayAdapter:

package com.bopbi.model;

import java.util.List;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;

import com.bopbi.R;

public class LocationAdapter extends ArrayAdapter {

	int resource;
	String response;
    Context context;
    private LayoutInflater mInflater;

	public LocationAdapter(Context context, int resource, List objects) {
		super(context, resource, objects);
		this.resource = resource;
		mInflater = LayoutInflater.from(context);
	}

	static class ViewHolder {
		TextView title;
		TextView description;
	}

	public View getView(int position, View convertView, ViewGroup parent)
    {
		ViewHolder holder;
        //Get the current location object
        LocationModel lm = (LocationModel) getItem(position);

        //Inflate the view
        if(convertView==null)
        {
            convertView = mInflater.inflate(R.layout.item, null);
			holder = new ViewHolder();
			holder.title = (TextView) convertView
					.findViewById(R.id.it_location_title);
			holder.description = (TextView) convertView
					.findViewById(R.id.it_location_description);

			convertView.setTag(holder);

        }
        else
        {
        	holder = (ViewHolder) convertView.getTag();
        }

        holder.title.setText(lm.getName());
		holder.description.setText(lm.getDescription());

		return convertView;
    }

}

and here is the main file, that later will be use to call the webservice using AsyncTask and display in onn a ListView

package com.bopbi.ui;

import java.util.ArrayList;

import com.bopbi.R;
import com.bopbi.model.LocationAdapter;
import com.bopbi.model.LocationList;
import com.bopbi.model.LocationModel;
import com.bopbi.util.RestClient;
import com.bopbi.util.RestClient.RequestMethod;
import com.google.gson.Gson;

import android.app.Activity;
import android.location.LocationManager;
import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.ListView;
import android.widget.TextView;

public class ListRest extends Activity {
	LocationManager lm;

	ArrayList locationArray = null;
	LocationAdapter locationAdapter;
	LocationList list;

	ListView lv;
	TextView loadingText;

	public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        lv = (ListView) findViewById(R.id.list_nearme);

        locationArray = new ArrayList();
        locationAdapter = new LocationAdapter(ListRest.this, R.layout.item, locationArray);

        lv.setTextFilterEnabled(true);
		lv.setAdapter(locationAdapter);

		try {
			new LocationSync().execute("http://vivid-snow-43.heroku.com/nearme.json");
		} catch(Exception e) {}
    }

	private class LocationSync extends AsyncTask<String, Integer, LocationList> {

		protected LocationList doInBackground(String... urls) {
			LocationList list = null;
			int count = urls.length;

	        for (int i = 0; i < count; i++) {
	        	try {

	    			RestClient client = new RestClient(urls[i]);

	    			try {
	    			    client.Execute(RequestMethod.GET);
	    			} catch (Exception e) {
	    			    e.printStackTrace();
	    			}

	    			String json = client.getResponse();

	    			list = new Gson().fromJson(json, LocationList.class);

	    		} catch(Exception e) {}
	        }
	        return list;
		}

		protected void onProgressUpdate(Integer... progress) {

	    }

	    protected void onPostExecute(LocationList loclist) {

	    	for(LocationModel lm : loclist.getLocations())
	        {
				locationArray.add(lm);
	        }
	        locationAdapter.notifyDataSetChanged();
	    }

	}
}

Layout File

the layout file is here, main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:orientation="vertical" android:layout_width="fill_parent"
	android:layout_height="fill_parent">
	<TextView android:layout_width="fill_parent"
		android:layout_height="wrap_content" android:text="Near Me" />
	<ListView android:id="@+id/list_nearme" android:divider="#FFCC00"
		android:dividerHeight="1dp" android:layout_width="fill_parent"
		android:layout_height="wrap_content"/>
</LinearLayout>

and the item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent">
  <TextView android:id="@+id/it_location_title" android:layout_width="wrap_content"
		android:layout_height="wrap_content" android:paddingLeft="10dp" android:paddingRight="10dp"
		android:textSize="20sp">
	</TextView>
	<TextView android:id="@+id/it_location_description" android:layout_width="wrap_content"
		android:layout_height="wrap_content" android:paddingLeft="10dp" android:paddingRight="10dp"
		android:textSize="14sp">
	</TextView>
</LinearLayout>

the complete source code