JSONArrayAdapter.java

package edu.mit.mobile.android.json;
/*
 * Copyright (C) 2011  MIT Mobile Experience Lab
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

import java.io.IOException;
import java.net.URI;

import org.apache.http.client.HttpClient;
import org.apache.http.client.HttpResponseException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.BasicResponseHandler;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;

import android.content.Context;
import android.os.AsyncTask;
import android.widget.BaseAdapter;

/**
 * An adapter for either a static JSONArray or a remote list that is loaded from a network.
 * If you need to do custom network requests, override getHttpClient() and getHttpGet().
 * You don't need to call them. 
 * 
 * @author steve
 *
 */
public abstract class JSONArrayAdapter extends BaseAdapter {
	
	private JSONArray ar;
	private LoadJSONArrayTask loadTask;
	
	public JSONArrayAdapter(Context context, JSONArray jsonArray) {
		ar = jsonArray;
	}
	
	public JSONArrayAdapter(Context context, URI remoteList){
		ar = new JSONArray(); // temporary until we get our content...
		loadTask = new LoadJSONArrayTask();
		loadTask.execute(remoteList);
	}
	
	public int getCount() {
		return ar.length();
	}
	
	public void setJSONArray(JSONArray jsonArray){
		ar = jsonArray;
		notifyDataSetChanged();
	}

	public Object getItem(int position) {
		try {
			return ar.get(position);
		} catch (final JSONException e) {
			
			e.printStackTrace();
			return null;
		}
	}

	public long getItemId(int position) {
		
		return position;
	}
	
	public HttpClient getHttpClient(){
		return new DefaultHttpClient();
	}
	
	public HttpGet getHttpGet(URI uri){
		return new HttpGet(uri);
	}
	
	public void onPreExecute(){
		
	}
	
	public void onPostExecute(JSONArray result){
		
	}
	
	private class LoadJSONArrayTask extends AsyncTask<URI, Double, JSONArray>{

		@Override
		protected void onPreExecute() {
			JSONArrayAdapter.this.onPreExecute();
		}
		
		@Override
		protected JSONArray doInBackground(URI... params) {
			JSONArray result = null;
			final HttpClient hc = getHttpClient();
			final HttpGet req = getHttpGet(params[0]);
			try {
				result = new JSONArray(hc.execute(req, new BasicResponseHandler()));
			} catch (final HttpResponseException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (final IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (final JSONException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			
			return result;
		}
	
		@Override
		protected void onPostExecute(JSONArray result) {
			JSONArrayAdapter.this.onPostExecute(result);
			
			if (result == null){
				return;
			}
			setJSONArray(result);
		}
	}
}