One important trick missing are delegated properties https://kotlinlang.org/docs/reference/delegated-properties.html

Instead of

var recyclerView: RecyclerView? = null
val adapter : Adapter? = null
fun onCreate() {
   setContentView(...)
   recyclerView = ....
   adapter = createAdapter()
   recyclerView!!.adapter = adapter!!
}

our code becomes something like

val recyclerView: RecyclerView by bindView(R.id.recycler)
val adapter : Adapter by lazy {
    createAdapter()
}
fun onCreate() {
   setContentView(...)
   reyclerview.adapter = adapter 
}

The first line use a delegated property provided by https://github.com/JakeWharton/kotterknife , the second use the lazy delegated property from kotlin stdlib

Benefits :

• you transform a nullable type in a non-nullable type
• you get rid of mutability (val vs var)
• you reduce the cognitive load by having the field declaration and initialisation grouped together.