2 basics: MainActivity.java and activity_main.xml which is code & layout
own editor how2: Android Studio/Settings/Plugins/Browse Repositories and search for IdeaVim.
class, method, attribute, pass parameter, return value
chap02
note: if need vi, then goto Android Studio/Preference/PlugIns_to_import_IdeaVim
use RelativeLayout instead of Contrain Layout
res / String.xml