abstract class to run in non-UI thread, and load an XML file into value objects

ActivityAsyncTask.java

/*
 * Copyright (c) 2011 Typeoneerror Studios LLC
 * $Id$
 */

package com.typeoneerror.apps.application.tasks;

import android.util.Log;
import com.typeoneerror.apps.application.io.ActivityFeedHandler;
import com.typeoneerror.apps.application.model.Model;
import com.typeoneerror.apps.application.utils.Constants;
import com.typeoneerror.apps.application.utils.HttpHelper;
import java.util.List;

/**
 * Using the AsyncTaskWithHandler to load recent activity in 
 * a thread that isn't UI.
 */
public class ActivityAsyncTask extends AsyncTaskWithHandler
{
    private static final String TAG = Constants.TAG + ActivityAsyncTask.class.getSimpleName();

    public ActivityAsyncTask(AsyncTaskCompleteListener<List<Model>> activity)
    {
        super(activity);
        setHandler(new ActivityFeedHandler());
    }

    @Override
    protected List<Model> doInBackground(String... params)
    {
        // load xml
        final HttpHelper helper = new HttpHelper();
        String response = helper.makeGetRequest("http://localhost/activity.xml");

        List<Model> result = null;

        try
        {
            parseResultUsingHandler(response);
            result = getHandler().getList();
            Log.i(TAG, "Number of events: " + result.size());
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
        return result;
    }
}

AsyncTaskWithHandler.java

/*
 * Copyright (c) 2011 Typeoneerror Studios LLC
 * $Id$
 */

package com.typeoneerror.apps.application.tasks;

import android.os.AsyncTask;
import android.util.Log;
import com.typeoneerror.apps.application.io.BasicDefaultHandler;
import com.typeoneerror.apps.application.model.Model;
import com.typeoneerror.apps.application.utils.Constants;
import java.io.StringReader;
import java.util.List;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.InputSource;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;

/**
 * An asynchronous task implementation using commonsguy's
 * technique for attaching and detaching the activity reference
 * so as to avoid a stranded reference to the context.
 * <p/>
 * After XML is loaded, it is parsed into a List of Models.
 * <p/>
 * https://github.com/commonsguy/cw-android/blob/master/Rotation/RotationAsync/src/com/commonsware/android/rotation/async/RotationAsync.java
 *
 * @author typeoneerror
 * @version 1.0
 */
abstract public class AsyncTaskWithHandler extends AsyncTask<String, Void, List<Model>>
{
    private static final String TAG = Constants.TAG + AsyncTaskWithHandler.class.getSimpleName();

    private AsyncTaskCompleteListener<List<Model>> activity;
    private BasicDefaultHandler                    handler;
    private boolean                                completed;

    public AsyncTaskWithHandler(AsyncTaskCompleteListener<List<Model>> activity)
    {
        attach(activity);
    }

    public void attach(AsyncTaskCompleteListener<List<Model>> activity)
    {
        this.activity = activity;
    }

    public void detach()
    {
        activity = null;
    }

    public BasicDefaultHandler getHandler()
    {
        return handler;
    }

    public boolean isCompleted()
    {
        return completed;
    }

    public void setHandler(BasicDefaultHandler handler)
    {
        this.handler = handler;
    }

    @Override
    protected void onPostExecute(List<Model> result)
    {
        completed = true;
        activity.onTaskComplete(result);
    }

    protected void parseResultUsingHandler(String result) throws Exception
    {
        if (handler == null)
        {
            throw new Exception("You must set a handler to parse XML results.");
        }

        try
        {
            SAXParserFactory factory = SAXParserFactory.newInstance();

            SAXParser parser = factory.newSAXParser();
            XMLReader reader = parser.getXMLReader();

            reader.setContentHandler((DefaultHandler) handler);

            InputSource source = new InputSource();
            source.setCharacterStream(new StringReader(result));
            reader.parse(source);
        }
        catch (Exception e)
        {
            Log.e(TAG, "XML Parsing Exception: " + e);
            e.printStackTrace();
        }
    }
}