MainActivity.kt

class MainActivity : AppCompatActivity() {

    private lateinit var viewPager: ViewPager2

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        viewPager = findViewById(R.id.my_view_pager)
        val tabLayout = findViewById<TabLayout>(R.id.tabs)
        val pagerAdapter = ScreenSlidePagerAdapter(this)
        viewPager.adapter = pagerAdapter
        TabLayoutMediator(tabLayout, viewPager) { tab, position ->
            when (position) {
                0 -> tab.text = "Home"
                1 -> tab.text = "School"
            }
        }.attach() //this replaces the tabLayout.setupWithViewPager() from ViewPager API
    }

    override fun onBackPressed() {
        if (viewPager.currentItem == 0) {
            super.onBackPressed() //if I'm in the first Fragment just go back
        } else {
            viewPager.currentItem = viewPager.currentItem - 1 //just slide to the first Fragment
        }
    }

    private inner class ScreenSlidePagerAdapter(fragmentActivity: FragmentActivity) : FragmentStateAdapter(fragmentActivity) {
        override fun getItemCount(): Int = 2 //because I have two Fragments

        override fun createFragment(position: Int): Fragment = if (position == 0) {
            HomeFragment()
        } else {
            SchoolFragment()
        }
    }
}