Seems many people are missing the overall point of the post: The APIs Android provides that are listed here are intended to be used as the glue between your app

Seems many people are missing the overall point of the post: The APIs Android provides that are listed here are intended to be used as the glue between your application and the rest of the system. However you want to build your application from that point on is up to you. In particular, Android Activities aren't simply a main() function because they are designed from a multitasking standpoint; users are going to be going in and out of apps, changing the state of the device (such as rotating the device), etc. In other application environments, you might register callbacks to fire when the window is hidden or gets resized. In Android those callbacks already exist and are set in stone to encourage apps to behave as a good citizen on a potentially resource-constrained mobile device. But as the post details, you don't have to do anything beyond properly managing heavy resources (like camera access) and saving and restoring state at the appropriate points if you don't want to.