Android Jetpack navigation, host fragment inside another host fragment

Question

I'm trying to achieve a simple design. One activity with a host fragment.

The thing is, one of the destinations has a bottom navigation bar.

Here's a paint sketch

After a little bit of research, I discovered that the best practice is to have a single Activity with a host fragment.

In my particular case, the bottom navigation bar should not be visible in the login and register fragments and just hiding it doesn't seem right to me.

I managed to create an activity with a bottom navigation bar connecting main fragment to frag 1, frag 2 or frag 3, but now I need to add the login fragment and register fragment and I'm not sure how to handle the navigation.

Here's the code for the app without the authentication fragments.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    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"
    android:orientation="vertical"
    tools:context=".Presentation.MainActivity">

    <androidx.appcompat.widget.Toolbar
        android:id="@+id/toolbar"
        app:title="Glucose Entries"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="?colorPrimary"
        android:theme="@style/ToolbarTheme"/>

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/bottom_nav"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:menu="@menu/bottom_navigation_bar"/>

    <fragment
        android:id="@+id/nav_host_fragment"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:name="androidx.navigation.fragment.NavHostFragment"
        app:navGraph="@navigation/mobile_navigation"
        app:defaultNavHost="true" />

</LinearLayout>

Also:

class MainActivity : AppCompatActivity() {

    private lateinit var navController: NavController

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

        navController = Navigation.findNavController(this, R.id.nav_host_fragment)
        bottom_nav.setupWithNavController(navController)
        NavigationUI.setupActionBarWithNavController(this, navController)
    }

    // stuff
}

And the navigation file:

<?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"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/mobile_navigation"
    app:startDestination="@id/mainListFragment">

    <!--frag 1 -->
    <fragment
        android:id="@+id/mainListFragment"
        android:name="com.gluco.Presentation.MainList.MainListFragment"
        android:label="Glucose Entries"
        tools:layout="@layout/main_list_fragment">
    </fragment>

    <!--frag 2 -->
    <fragment
        android:id="@+id/statisticsFragment"
        android:name="com.gluco.Presentation.Statistics.StatisticsFragment"
        android:label="statistics_fragment"
        tools:layout="@layout/statistics_fragment" />

    <!--frag 3 -->
    <fragment
        android:id="@+id/settingsFragment"
        android:name="com.gluco.Presentation.Settings.SettingsFragment"
        android:label="SettingsFragment" />

</navigation>

Should I just hide the navigation bar on fragments where is not supposed to be?

Also, I'm thinking another solution could be to not use the automatic navigation provided from the bottom navigation bar and create my own actions to navigate from main fragment to frag 1, frag 2 or frag 3

Answer 1

Imho, it sounds fine to me to have your single activity be the source of truth as to which fragment shows and hides the navigation bar.