title: Update tabs from a tab's activity in a Android TabHost
body: <p>I have a TabActivity and am going to have 3 or 4 tabs.</p>
  
  <p>In TabA, I would like to have an ExpandableListView, which will list products. I would like TabC to act as a sort of "shopping cart", probably with a ListView of itself. </p>
  
  <p>Is there a way to interact with the TabHost from the Activity? I would like to be able to click a button inside of TabA and have it update and switch to TabC. Is this possible? Can I get the Tab's activities call its parents methods?</p>