Android TabLayout with icons and color state list

IconTabLayout.kt

/**
 * IconTabLayout is an extension of TabLayout and enables us to use icons instead of 
 * text for the tabs. To reuse a single icon for different states we simply tint it
 * with color state list. I use vector drawables for icons.
 */
class IconTabLayout : TabLayout {

    private var viewPager: ViewPager? = null

    constructor(context: Context) : super(context)
    constructor(context: Context, attributeSet: AttributeSet) : super(context, attributeSet)
    constructor(context: Context, attributeSet: AttributeSet, defStyleAttr: Int) : super(context, attributeSet, defStyleAttr)

    override fun onAttachedToWindow() {
        if (viewPager == null) {
            if (parent is ViewPager) viewPager = parent as ViewPager
        }
        super.onAttachedToWindow()
    }

    override fun setupWithViewPager(viewPager: ViewPager?, autoRefresh: Boolean) {
        this.viewPager = viewPager
        super.setupWithViewPager(viewPager, autoRefresh)
    }

    override fun addTab(@NonNull tab: Tab, position: Int, setSelected: Boolean) {
        if (viewPager != null && viewPager!!.adapter is TabPagerAdapter) {
            val icon: Drawable = DrawableCompat.wrap((viewPager!!.adapter as TabPagerAdapter).getPageIcon(context, position))
            DrawableCompat.setTintList(icon.mutate(), ContextCompat.getColorStateList(context, R.color.tab_color))
            tab.icon = icon
        }
        super.addTab(tab, position, setSelected)
    }
}

TabPagerAdapter.kt

/**
 * TabPagerAdapter provides fragments and icons for TabLayout
 */
class TabPagerAdapter(fm: FragmentManager) : FragmentPagerAdapter(fm) {

    override fun getCount(): Int = 2

    override fun getItem(position: Int): Fragment = when (position) {
        0 -> YourFragment.newInstance()
        else -> YourFragment.newInstance()
    }

    fun getPageIcon(context: Context, position: Int): Drawable = when (position) {
        0 -> ContextCompat.getDrawable(context, R.drawable.ic_whatshot)
        else -> ContextCompat.getDrawable(context, R.drawable.ic_local_bar)
    }
}