This is the post I wish existed when I was looking for how to do this simple thing. I spent hours reading around trying to figure out how to show my app is busy, but to no avail.
Last week I finally got around to downgrading my laptop from karmic to jaunty.
Once I got witter to the point that it had multiple views, I immediately wanted to have a nice way to switch between those views. In the first instance I just used buttons which have the advantage of being able to go direct to the view you want, but at the cost of screen space to show the button.