Sample.kt

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val fragment = MainFragment()
        supportFragmentManager.beginTransaction()
            .replace(R.id.container, fragment)
            .commit()
    }

    override fun onBackPressed() {
        if (!onBackPressedDispatcher.hasEnabledCallbacks()) {
            // handle activity back press when no other dispatch enabled
            Log.e(MainActivity::class.java.simpleName, "MainActivity handleOnBackPressed")
        }
        super.onBackPressed()
    }
}

class MainFragment : Fragment(R.layout.fragment_main) {

    private lateinit var callback: OnBackPressedCallback

    override fun onAttach(context: Context) {
        super.onAttach(context)
        callback = object : OnBackPressedCallback(true) {
            override fun handleOnBackPressed() {
                Log.e(MainFragment::class.java.simpleName, "MainFragment handleOnBackPressed")
                // do something and release back press call back
                callback.isEnabled = false
            }
        }
        requireActivity().onBackPressedDispatcher.addCallback(callback)
    }
}