LiveStreamActivity.kt

class LiveStreamActivity : AppCompatActivity(R.layout.activity_main) {
    private val adapter = MessagesListAdapter()

    private val messageListSmoothScroller by lazy {
        object : LinearSmoothScroller(this) {
            val MILLISECONDS_PER_INCH = 400f

            override fun calculateSpeedPerPixel(displayMetrics: DisplayMetrics?): Float {
                return MILLISECONDS_PER_INCH / displayMetrics!!.densityDpi
            }
        }
    }
    ...
}