I was only able to get the visual preview of the two panes after I added the following to my layout (using both API 19 on a RazrM, and API 21 on a Nexus 10 tablet):
<?xml version="1.0" encoding="utf-8"?>
You can see the barely detectable divider (which actually looks like it is 1/4 of the way over, not 1/3 by the way):
However, when I run the app, the CrimeListFragment still takes up the entire screen:
Is this expected behavior?