How can I implement a Timer / TimerTask that runs AsyncTask? (Android)

I am trying to execute a task (i.e. load data from a text file) asynchronously and repeatedly at the specified time (i.e. every few seconds, although this speed may change at runtime).

I did some research and decided that this would require either AsyncTask or a separate thread. I decided to use AsyncTask for simplicity.

Now I need to execute this AsyncTask according to the re-timer schedule. I believe I should use Timer and TimerTask.

The code below is a simple form of what I'm trying to achieve. When I try to run this code using the Android emulator (via the Eclipse IDE), I get the following message: "Sorry! The application stopped unexpectedly. Try again."

I would like to know where the problem is and how I can fix it. Thank!

public class Sample extends Activity {

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

    SimpleTimerTask myTimerTask = new SimpleTimerTask(); 

    long delay = 0;
    long period = 5000;

    Timer myTimer = new Timer();
    myTimer.schedule(myTimerTask, delay, period);
}


private class SimpleAsyncTask extends AsyncTask<Void, Void, Void> {
    protected Void doInBackground(Void... params) {
        return null;
    }   
}


private class SimpleTimerTask extends TimerTask {
    public void run() {
        new SimpleAsyncTask().execute();
    }       
}

}

EDIT: Here are the LogCat posts that seem relevant

FATAL EXCEPTION: Timer-0

java.lang.ExceptionInInitializerError

at ...

Called: java.lang.RuntimeException: cannot create a handler inside a thread that did not call Looper.prepare ()

at ...