just remove TODO( ... ) from your onClickListener:

​

override fun onClick(v: View?) {

    // No TODO here

    when (v?.id) {

        ...

    }

}

TODO(...) is Kotlin function which always throws NotImplementedError. If you want to mark something with TODO but to not throw exception - just use TODO with comments:

​

override fun onClick(v: View?) {

    //TODO: implement later

    when (v?.id) {

        ...

    }

}

override fun onClick(v: View?) {

    // No TODO here

    when (v?.id) {

        ...

    }

}