Q:

Why do subclasses of android classes not require calling of super-constructor?

I've noticed that classes that subclass android classes don't require having a constructor and calling the constructor of the superclass. Why is that? I thought all classes except pojo's needed a constructor?

A:

Because you're not overriding the constructor. There's no requirement* saying you need to override the constructor of the superclass.

I thought all classes except pojo's
  needed a constructor?

They have a constructor. It's inherited from their parent class. You're just not REIMPLEMENTING the constructor.
*As noted by @Christian, you would need to implement a constructor if the parent class's constructor took arguments. In the case of android classes (most), they don't.

