kotlin fun <T : Fragment> T.withArguments(vararg params: Pair<String, Any?>): T { arguments = bundleOf(*params) return this } val fragment = MyFragment().withArguments("param1" to 1, "param2" to "hello") fragment.transaction { replace(R.id.container, fragment) addToBackStack(null) } override fun onSaveInstanceState(outState: Bundle) { super.onSaveInstanceState(outState) outState.putInt("count", count) } override fun onViewStateRestored(savedInstanceState: Bundle?) { super.onViewStateRestored(savedInstanceState) count = savedInstanceState?.getInt("count") ?: 0 }