A modern programming language that makes developers happier.

kotlinlang

Okay, now I see what you mean. The first paragraph mostly screams "MV*", so no questions here.

As for the second part, I understand the idea behind similar contracts of checkbox and toggle button, my question was mostly regarding implementation details -- since Kotlin doesn't have neither type classes nor structured polymorphism, I don't see an ability to mix in new interface into existing class. So you have to go Anko's approach of second view hierarchy, at least for widgets that clearly have contracts you're defining. Or am I missing something?