init_view_pager.kt

override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        initViewPager()
    }

    private fun initViewPager() {
        val pageAdapter = PageAdapter(listOf(Item(Color.RED), Item(Color.BLUE), Item(Color.GREEN)))
        viewPager2.offscreenPageLimit = 2
        viewPager2.orientation = ViewPager2.ORIENTATION_VERTICAL
        viewPager2.adapter = pageAdapter
        viewPager2.currentItem = pageAdapter.getMiddlePosition()
    }