A modern programming language that makes developers happier.

kotlinlang

This approach has several problems:
1) You cannot separately test `Activity` and `GpsService` without some really verbose DI setup which would not be needed if you could simply pass `GpsService` in constructor;
2) Your activity now should know about `GpsService` internal details, at least about its `requestCode` and `resultCode` in order to determine that the result in `onActivityResult()` is from `GpsService` request;
3) `GpsService` is now concerned with `Activity` details such as `requestCode` and `resultCode`