How to Hide Bottom Bar Nav.. When following single Activity design?

Question

I am trying to show thebottom bar navigation in only a few fragments (i.e hide it for most of my fragments)..

I read the official document about this, but it unclear to me, like where do I put the code, and I read comments on this here on StackOverFlow, like "I'm surprised this is suggested in the docs because it actually looks pretty terrible since the listener fires before the new fragment is placed on the screen, causing a visible flicker (that's sometimes there, sometimes not)".

I've research about this, and from my understanding I need to create a nested naviagtion_graph (navigation), or something, listen to onDestinationChanged and set bottom nav or toolbar to Gone..

I don't really understand this.. I just want to hide the bottom bar nav in most of the fragments..

Here's my navigation_gragh (mobile_navigation) :

<navigation 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:id="@+id/mobile_navigation"
    app:startDestination="@+id/navigation_home">

    <fragment
        android:id="@+id/navigation_home"
        android:name="com.example.testingbottomnav.ui.home.HomeFragment"
        android:label="@string/title_home"
        tools:layout="@layout/fragment_home" >
        <action
            android:id="@+id/action_navigation_home_to_newScreenFragment"
            app:destination="@id/newScreenFragment" />
    </fragment>

    <fragment
        android:id="@+id/navigation_dashboard"
        android:name="com.example.testingbottomnav.ui.dashboard.DashboardFragment"
        android:label="@string/title_dashboard"
        tools:layout="@layout/fragment_dashboard" />

    <fragment
        android:id="@+id/navigation_notifications"
        android:name="com.example.testingbottomnav.ui.notifications.NotificationsFragment"
        android:label="@string/title_notifications"
        tools:layout="@layout/fragment_notifications" />
    <fragment
        android:id="@+id/newScreenFragment"
        android:name="com.example.testingbottomnav.ui.newscreen.NewScreenFragment"
        android:label="fragment_new_screen"
        tools:layout="@layout/fragment_new_screen" />
</navigation>

Here's my activity_main.xml :

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingTop="?attr/actionBarSize">

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/nav_view"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="0dp"
        android:layout_marginEnd="0dp"
        android:background="?android:attr/windowBackground"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:labelVisibilityMode="selected"
        app:menu="@menu/bottom_nav_menu" />

    <fragment
        android:id="@+id/nav_host_fragment_activity_main"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true"
        app:layout_constraintBottom_toTopOf="@id/nav_view"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:navGraph="@navigation/mobile_navigation" />

</androidx.constraintlayout.widget.ConstraintLayout>

And here's my MainActivty.kt :

class MainActivity : AppCompatActivity() {

    private lateinit var binding: ActivityMainBinding

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

        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        val navView: BottomNavigationView = binding.navView

        val navController = findNavController(R.id.nav_host_fragment_activity_main)
        // Passing each menu ID as a set of Ids because each
        // menu should be considered as top level destinations.
        val appBarConfiguration = AppBarConfiguration(
            setOf(
                R.id.navigation_home, R.id.navigation_dashboard, R.id.navigation_notifications
            )
        )
        setupActionBarWithNavController(navController, appBarConfiguration)
        navView.setupWithNavController(navController)
    }
}

Any help would be much appreciated, thanks..

Answer 1

I added this line of code to the onCreate method:

// hiding bottom bar
    navController.addOnDestinationChangedListener { _, nd: NavDestination, _ ->
        // the IDs of fragments as defined in the `navigation_graph`
        if (nd.id == R.id.navigation_home || nd.id == R.id.navigation_dashboard
            || nd.id == R.id.navigation_notifications
        ) {
            navView.visibility = View.VISIBLE
        } else {
            navView.visibility = View.GONE
        }
    }