How does buying an app to enable paid features of another app work?

Question

There are apps (such as https://play.google.com/store/apps/details?id=com.teslacoilsw.launcher) that are free, but whose paid features can be enabled by buying another app (in this case, this one https://play.google.com/store/apps/details?id=com.teslacoilsw.launcher.prime)

How does this work?

My guess is that the free apps launches an explicit Intent and can detect if the app is present via a try/catch structure. The downside of this is that this could be easily circunvented by someone who creates an app with the same package name and specifies all possible Intent filters.

Is this how it works, or is it some other way?

Answer 1

There are various ways to do that. One way is to query a content provider which will be protected with a special permission.

I have released quite long ago on Github a library which helps doing this: Android Unlocker Library.

That's a good option if you are dealing with devices outside the Google ecosystem, however, from a developer experience, in-app purchases offer a much better user experience (and thus drive more sales) according to me.