Default language defines current locale for application.
Most multi-language applications simply read settings and use appropriate resources. For example:
Dim jo As JavaObject
jo.InitializeStatic ("java.util.Locale")
Log (jo.RunMethodJO ("getDefault", Null).RunMethod ("getISO3Language", Null))
Log (jo.RunMethodJO ("getDefault", Null).RunMethod ("getDisplayLanguage", Null))
Of course, Android offers a way to set locale in run-time. But it's not for lazy due to permanent changes in API.
For example
https://github.com/gunhansancar/Cha...hangelanguageexample/helper/LocaleHelper.java
Well, I did small library and sample (attached). They more or less work, but require some corrections, first of all, for API 26+. Probably, tomorrow evening I will clean a project.