I just wanted to share that I finally have been able to get the basics of my app up and running, thanks in VERY large part to the help I've received here.
It's nothing much so far: It displays a splash screen and checks to see if you have a valid session token. If you do, it takes you to the home screen. If you don't, it takes you to a login screen, where a valid login will then give you a session token and take you to the home screen.
If I were doing this with HTML/javascript, or Python, or plain Java, not that big a deal, but with the complexities I've discovered in Android development, I'm pretty happy with what I've done.
I now have a full framework, including a number of abstracted and helper classes, to rather quickly develop the rest of my app, and hopefully several more to come!
Again thank you for all the help, and a special shout-out to
@LV426 for helping me with my HTTP woes.