How to keep a specific screen when using Navigatioin Component?

Question

I have a BottomNavigationView and I am using a NavController to switch menus and move the screen.

I would like to know how to keep a specific screen even when moving the menu freely.

Let me explain in more detail.

There are bottom menus A, B, C. And each has a Fragment screen.

All menus and screen transitions use NavHost, NavController, and nav_graph.

In menu C, a dialog is displayed through the button on the C screen.

The dialog is also linked to the nav_graph.

When an option is selected in the dialog, it moves to screen D.

D screen is the page where you write something.

This is important from now on.

The current menu is C, screen D is open, and something is being written.

However, if you go to another menu while writing and then return to C, screen C of the first menu C appears, not the screen you are writing.

Here, I want the screen I was writing to continue to be displayed even when I return from another menu.

Any good way?

For reference, since I am using the mvvm pattern and viewmodel, the data of the screen I am writing seems to be maintained.

Thank you.

nav_graph

<?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/nav_graph"
    app:startDestination="@id/calendar">

    <!-- menu C screen   -->
    <fragment
        android:id="@+id/write_home"
        android:name="com.example.writeweight.fragment.WriteRoutineHomeFragment"
        android:label="fragment_write_routine_home"
        tools:layout="@layout/fragment_write_routine_home" >
        <action
            android:id="@+id/action_write_home_to_bodyPartDialog"
            app:destination="@id/bodyPartDialog" />
    </fragment>

    <!-- dialog -->
    <dialog
        android:id="@+id/bodyPartDialog"
        android:name="com.example.writeweight.fragment.BodyPartDialogFragment"
        android:label="BodyPartDialogFragment"
        tools:layout="@layout/fragment_body_part_dialog">
        <action
            android:id="@+id/action_bodyPartDialog_to_write"
            app:destination="@id/write"/>
    </dialog>

    <!-- screen D (write page) -->
    <fragment
        android:id="@+id/write"
        android:name="com.example.writeweight.fragment.WriteRoutineFragment"
        android:label="WritingRoutineFragment"
        tools:layout="@layout/fragment_writing_routine">
        <action
            android:id="@+id/action_write_to_workoutListTabFragment"
            app:destination="@id/workoutListTabFragment" />
        <argument
            android:name="title"
            app:argType="string"
            app:nullable="true"
            android:defaultValue="@null"/>
        <argument
            android:name="workout"
            app:argType="string"
            app:nullable="true"
            android:defaultValue="@null"/>
    </fragment>
</navigation>

Answer 1

There are two ways to fix this issue either use version_navigation 2.4.0-alpha01 which is the easiest way or use NavigationExtensions to use NavigationExtensions you have to add this to your project NavigationExtensions and then in the navigation menu create separate navigation files for each tab. In the main activity, layout replace fragment with FragmentContainerView and remove NavHostFragment.

In the Mainactivty

class MainActivity : AppCompatActivity(), NavController.OnDestinationChangedListener {
private val viewModel by viewModels<MainViewModel>()
private var currentNavController: LiveData<NavController>? = null

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

    /*
    appBarConfiguration = AppBarConfiguration(
        // navController.graph,
        setOf(
             R.id.navigate_home, R.id.navigate_collection, R.id.navigate_profile
        ),
        drawerLayout
    )

    setupActionBarWithNavController(navController, appBarConfiguration)
    navView.setupWithNavController(navController)
    bottomNavView.setupWithNavController(navController)

    // make sure appbar/toolbar is not hidden upon fragment switch
    navController.addOnDestinationChangedListener { controller, destination, arguments ->
        if (destination.id in bottomNavDestinationIds) {
            appBarLayout.setExpanded(true, true)
        }
    }
     */
     // Add your tab fragments

    val navGraphIds = listOf(R.navigation.home, R.navigation.albumlist, R.navigation.test)
    val controller = bottomNavView.setupWithNavController(
        navGraphIds = navGraphIds,
        fragmentManager = supportFragmentManager,
        containerId = R.id.nav_host_container,
        intent = intent
    )
    // Whenever the selected controller changes, setup the action bar.
    controller.observe(this, Observer { navController ->

        setupActionBarWithNavController(navController)
        // optional NavigationView for Drawer implementation
        // navView.setupWithNavController(navController)

        addOnDestinationChangedListener(navController)
    })
    currentNavController = controller
}

private fun addOnDestinationChangedListener(navController: NavController) {
    // ensure only one listener is active
    navController.removeOnDestinationChangedListener(this)
    navController.addOnDestinationChangedListener(this)
}

override fun onDestinationChanged(
    controller: NavController,
    destination: NavDestination,
    arguments: Bundle?
) {
    if (destination.id in bottomNavDestinationIds) {
        appBarLayout.setExpanded(true, true)
    }
}}