Yeah, fortunately this is not how software works in practice. The best example is probably the PC market, which is fragmented to such a degree that the hardware permutations are uncountable -- and yet Windows, Linux, other major operating systems and applications all manage to deliver stable, consistent user experiences. The situation with Android is parallel: lots of different hardware, but basically still a "write once, run everywhere" environment. (Everywhere being any phone with a legit Android environment.) Similarly to when you're developing on a PC, you occasionally need to know something about the specific hardware or version you're running against, but more often than not, you just code, and it just works.