TabsTransformer.kt

tabsRecyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
    override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
        totalTabsScroll += dx
    }
})

viewPager.registerOnPageChangeCallback(object : ViewPager2.OnPageChangeCallback() {
    override fun onPageScrolled(position: Int, positionOffset: Float, positionOffsetPixels: Int) {
        // Scroll tabs as viewpager is scrolled
        val dx = (position + positionOffset) * tabItemWidth - totalTabsScroll
        tabsRecyclerView.scrollBy(dx.toInt(), 0)

        // This acts like a page transformer for tabsRecyclerView. Ideally we should do this in the
        // onScrollListener for the RecyclerView but that requires extra math. positionOffset
        // is all we need so let's use that to apply transformation to the tabs

        val currentTabView = tabsRecyclerView.layoutManager?.findViewByPosition(position)!!
        val nextTabView = tabsRecyclerView.layoutManager?.findViewByPosition(position + 1)

        val defaultScale: Float = FiltersTabsAdapter.defaultScale
        val maxScale: Float = FiltersTabsAdapter.maxScale

        currentTabView.setScale(defaultScale + (1 - positionOffset) * (maxScale - defaultScale))
        nextTabView?.setScale(defaultScale + positionOffset * (maxScale - defaultScale))

        currentTabView.findViewById<View>(R.id.tab_pill).backgroundTintList =
                ColorStateList.valueOf(blendColors(tabColor, tabSelectedColor, 1 - positionOffset))
        nextTabView?.findViewById<View>(R.id.tab_pill)?.backgroundTintList =
                ColorStateList.valueOf(blendColors(tabColor, tabSelectedColor, positionOffset))
    }
})