Implement only one method from interface in anonymous class [duplicate]

Question

Is it possible in Kotlin to create an anonymous class implementing a certain interface and only implement the functions you'll need? For example I want to create a class implementing AnimationListener which has 3 methods:

• onAnimationStart
• onAnimationEnd
• onAnimationRepeat

If I only want to use the onAnimationEnd callback, can I just do something like this?

object : AnimationListener {
    override fun onAnimationEnd() {
        //my implementation
    }
}

The way I've done this in Java was by creating a class which implemented the interface, just create anonymous class of that class and override the methods I need. I was hoping Kotlin has a better, less verbose, approach on this.

Answer 1

I don't expect there's anything in Kotlin different to Java in this respect. You can, however, create your own interfaces that have default no-op implementation of methods you don't need :

interface AnimationEndListener : AnimationListener {
  fun onAnimationStart() {}
  fun onAnimationRepeat() {}
}

Then actual concrete implementation will extend AnimationEndListener and override only what's needed.