What's the standard way of swapping between UI elements in an activity in Android?
<p>I have an activity that has several views. Most of the views will remain constant, but there's one area which has different views based on the actions of the user. In other words, we might start out with 3 buttons and then switch to a countdown timer when one is clicked. I don't think it makes sense to create different activities, since most of the UI (and logic) is shared.</p>

<p>What's the standard approach to this in Android? I'm really new to the platform.</p>
