A working model of how an Android app runs: as a city. Pick a district up top; press the buttons; watch what the OS does. Early prototype: expect inaccuracies, corrections welcome.
GitHub · Android flow reference · inspired by PGSimCity
Early prototype, and the model simplifies a lot. If something here is wrong, or you want to add a piece of Android that's missing, open an issue or send a PR. Corrections are the most useful thing you can give it.