Mastering Kotlin

Responding to click events

When writing Android View code with Kotlin, we can set click listeners on our Views using a lambda rather than an anonymous inner class, shown as follows:

button.setOnClickListener {     // handle the event}

The lack of parentheses here makes this easier to read and to write. Additionally, we could combine this click listener lambda with a functional property for responding to the click:

var clickHandler: (() -> Unit)? = null...button.setOnClickListener {    // handle the event    clickHandler?.invoke()}

By exposing a public function property for responding to the click event, we can easily defer to that property within Button click listener and invoke the callback function only if it's non-null.