Fragment + Navigation Graph

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/nav_host_fragment"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true"
        app:navGraph="@navigation/mobile_navigation"/>

    <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)
        }
    }

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

    fun setUpNavigation() {
        val navHostFragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHostFragment?
        NavigationUI.setupWithNavController(bottom_navigation, navHostFragment!!.navController)
    }
}

mobile_navigation.xml

<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto" android:id="@+id/mobile_navigation.xml"
    app:startDestination="@id/page_1">

    <fragment
        android:id="@+id/page_1"
        android:name="com.eseo.myapplication2.ui.bottom.fragment.Page1"
        android:label="Page1" />
    <fragment
        android:id="@+id/page_2"
        android:name="com.eseo.myapplication2.ui.bottom.fragment.Page2"
        android:label="Page2" />
</navigation>

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()
    }
}