lateinit.kt

class MainActivity : AppCompatActivity() {
  ...
  private lateinit var recyclerView: RecyclerView
  
  override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        
        recyclerView = findViewById<RecyclerView>(R.id.main_rv).apply {
            setHasFixedSize(true)
            layoutManager = viewManager // recyclerView.layoutManager = viewManager
            adapter = viewAdapter // recyclerView.adapter = viewAdapter
        }
  }