Kotlin Android Extensions ViewBinding works by default for Activity and Fragment.
import kotlinx.android.synthetic.main.activity_main.*class TestActivity : Activity() {    override fun onCreate(savedInstanceState: Bundle?) {        super.onCreate(savedInstanceState)        setContentView(R.layout.activity_main)        // Instead of findViewById<TextView>(R.id.textView)        textView.setText("Hello world!")    }}To make it work for ViewHolder in RecyclerView, use LayoutContainer.
Edit build.gradle (Module)
androidExtensions {
    // https://kotlinlang.org/docs/tutorials/android-plugin.html#experimental-mode
    experimental = true
}class LocalListAdapter() : RecyclerView.Adapter<LocalListAdapter.ViewHolder>() {    override fun onBindViewHolder(holder: ViewHolder, position: Int) {        holder.apply {            textView.text = "Hello"        }    }    inner class ViewHolder(override val containerView: View) : RecyclerView.ViewHolder(containerView), LayoutContainer}NOTE: You can access view in ViewHolder by holder.itemView.textView (without LayoutContainer), but it doesn't comes with View Caching