expandItem.kt

private fun expandItem(holder: ListViewHolder, expand: Boolean, animate: Boolean) {
    if (animate) {
        val animator = getValueAnimator(
                expand, listItemExpandDuration, AccelerateDecelerateInterpolator()
        ) { progress ->
            holder.cardContainer.layoutParams.height =
                    (originalHeight + (expandedHeight - originalHeight) * progress).toInt()
            holder.cardContainer.layoutParams.width =
                    (originalWidth + (expandedWidth - originalWidth) * progress).toInt()

            holder.cardContainer.setBackgroundColor(blendColors(originalBg, expandedBg, progress))
            holder.cardContainer.requestLayout()

            holder.chevron.rotation = 90 * progress
        }

        if (expand) animator.doOnStart { holder.expandView.isVisible = true }
        else animator.doOnEnd { holder.expandView.isVisible = false }

        animator.start()
    } else {
      // ... Left out for brevity
    }
}