Android :: Make ListView Update Itself Periodically?

I never got this working in a straightforward manner. Sorry if I'm being a little vague. I'll try to elaborate on what I'm trying to do. I am trying to build a listview that grabs its data from a webservice. Once I initialize a listview, I want to keep polling the webserver periodically and update the contents of the listview. For this I am doing something like this:

public class SampleAutoUpdateList extends Activity {

//Autoupdate handler
private Handler handler = new Handler();
private Runnable updater = new Runnable() {

public void run() {

/*
* Update the list
*/..................................