Fragment multiple tabs without remove or replace

MainActivity.kt

class MainActivity : AppCompatActivity() {
    private lateinit var swipeFragment: SwipeFragment
    private lateinit var favoritesFragment: FavoritesFragment
    private lateinit var newsFragment: NewsFragment

    private val fragments: Array<out Fragment> get() = arrayOf(swipeFragment, favoritesFragment, newsFragment)

    private fun selectFragment(selectedFragment: Fragment) {
        var transaction = supportFragmentManager.beginTransaction()
        fragments.forEachIndexed { index, fragment ->
            if(selectedFragment == fragment) {
                transaction = transaction.attach(fragment)
                selectedIndex = index
            } else {
                transaction = transaction.detach(fragment)
            }
        }
        transaction.commit()
    }

    private var selectedIndex = 0

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

        if (savedInstanceState == null) {
            swipeFragment = SwipeFragment()
            favoritesFragment = FavoritesFragment()
            newsFragment = NewsFragment()

            supportFragmentManager.beginTransaction()
                .add(R.id.fragment_on_display, swipeFragment, "swipe")
                .add(R.id.fragment_on_display, favoritesFragment, "favorites")
                .add(R.id.fragment_on_display, newsFragment, "news")
                .commitNow()
        } else {
            selectedIndex = savedInstanceState.getInt("selectedIndex", 0)

            swipeFragment = supportFragmentManager.findFragmentByTag("swipe") as SwipeFragment
            favoritesFragment = supportFragmentManager.findFragmentByTag("favorites") as FavoritesFragment
            newsFragment = supportFragmentManager.findFragmentByTag("news") as NewsFragment
        }

        val selectedFragment = fragments[selectedIndex]

        selectFragment(selectedFragment)

        val homeButton = findViewById<ImageButton>(R.id.home_button)
        homeButton.setOnClickListener{
            selectFragment(swipeFragment)
        }

        val listButton = findViewById<ImageButton>(R.id.list_button)
        listButton.setOnClickListener {
            selectFragment(favoritesFragment)
        }

        val newsButton = findViewById<ImageButton>(R.id.news_button)
        newsButton.setOnClickListener {
            selectFragment(newsFragment)
        }
    }

    override fun onSaveInstanceState(bundle: Bundle) {
        super.onSaveInstanceState(bundle)
        bundle.putInt("selectedIndex", selectedIndex)
    }
}

Quick question, fragmentTransaction.detach() destroys the view hierarchy associated with the fragment so won't this be costly as opposed to just adding the fragments to the container and hiding/showing them when needed?

@GibsonRuitiari i always use attach/detach in samples because otherwise people would complain that their LiveData observers still work even while the fragment is hidden, as the fragment being hidden doesn't make them onStop'ped. This is because a Fragment can only be onStop'd while also destroying its view.

If you need to make it faster because inflation is costly, then replace attach/detach with show/hide.

Apply Changes and restart activity:
Unable to destroy activity Can not perform this action after onSaveInstanceState