One of the peculiar aspects of Android is that theoretically, everything is replaceable. This includes phone features, which initially seems odd, the fact that you can replace your phone dialler with something else.
I have completed the iOS version of Answers Against Humanity, it is currently in the App Store submission process, but I am thinking it might be rejected due to the content.
Any Android app that requires even a basic interface will need the basic building blocks of activities and intents to manage interface screens and the flow between them. In this video we look at the different activity types available and how we connect them with intents.
Notifications: you probably love them or hate them. I like them when they are useful to me, and this is something that the OpenBack SDK attempts to solve. It offers a framework for you to make your in-app notifications more than annoying notices, but tailoring them to users contexts and allowing them to do more with notifications.