La version à l'ancienne

activity_bottom.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ui.bottom.BottomActivity">

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/frame"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toTopOf="@id/bottom_navigation"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/bottom_navigation"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:menu="@menu/bottom_navigation_menu" />

</androidx.constraintlayout.widget.ConstraintLayout>

bottom_navigation_menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/page_1"
        android:enabled="true"
        android:icon="@drawable/ic_baseline_all_inclusive_24"
        android:title="@string/app_name"/>
    <item
        android:id="@+id/page_2"
        android:enabled="true"
        android:icon="@drawable/ic_baseline_all_inclusive_24"
        android:title="@string/app_name"/>
</menu>

BottomActivity.kt

class BottomActivity : AppCompatActivity() {
    companion object {
        fun getStartIntent(context: Context): Intent {
            return Intent(context, BottomActivity::class.java)
        }
    }

    private var page1Instance = Page1.newInstance()
    private var page2Instance = Page2.newInstance()

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

        showFragment(page1Instance)
        bottom_navigation.setOnNavigationItemSelectedListener { item ->
            when (item.itemId) {
                R.id.page_1 -> {
                    // Item 1 action
                    showFragment(page1Instance)
                    true
                }
                R.id.page_2 -> {
                    // Item 1 action
                    showFragment(page2Instance)
                    true
                }
                else -> false
            }
        }

    }


    private fun showFragment(fragment: Fragment) {
        supportFragmentManager.commit {
            setReorderingAllowed(true)
            replace(R.id.frame, fragment, fragment.tag)
        }
    }
}

Page1.kt

class Page1 : Fragment() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
    }

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_page1, container, false)
    }

    companion object {
        fun newInstance() = Page1()
    }
}