UsingFragmentFactory.kt

class MainActivity : AppCompatActivity() {
	
  private val mainfactory = MainFragmentFactory("Now this won't crash")
  private lateinit var mainFragment: MainFragment
	
  override fun onCreate(savedInstanceState: Bundle?) {
    supportFragmentManager.factory = mainfactory //This has to be done before super call
    super.onCreate(savesInstanceState)
    
    mainFragment = supportFragmentManager.fragmentFactory.instantiate(classLoader, MainFragmentFactory::class.java.name)
    
    supportFragmentManager.beginTransaction()
	      .add(R.layout.fragmentContainerView, mainFragment)
	      .commit()	
    }
}

class MainFragmentFactory(val textToDisplay: String): FragmentFactory() {
  override fun instantiate(classLoader: ClassLoader, className: String): Fragment {
    return when(className) {
        NotificationFragment::class.java.name -> MainFragment(textToDisplay)
        else -> super.instantiate(classLoader, className)
     }
   }
}

class MainFragment(val textToDisplay: String) : Fragment() {
    // Same as earler, no changes
}