Unexpected BottomNavigationView behavior: bottom tab bar creates new screen each time user click on menu item

Question

I want to create user flow like this: Login screen (w/o navigation bar) -> Home Screen (with navigation bar, includes backstacks for Album and Profile)

Application starts with an authentication screen. When the user clicks “Login” - I remove it from backstack using “to_albums_action” and navigate to the albums screen.

Everything works great except strange stack behavior. When the user goes from Albums to Profile, when clicks Albums again - android opens it as a new instance.

So, when the user goes: Albums -> Profile -> Albums, then starts pressing the back button he starts hopping back: -> Profile -> Albums -> Homescreen.

Expected behavior is: go directly to Homescreen, as Albums is the first element in the menu.

Digging around, I found that this behavior could be fixed if I won’t remove auth_nav from backstack. Maybe, because NavController calculates all includes for the menu. I also noticed this in logs:

I/NavController: Ignoring popBackStack to destination com.project:id/signin_dest as it was not found on the current back stack

There some of my files:

main_nav.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"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main_nav">
    <include app:graph="@navigation/auth_nav" />
    <include app:graph="@navigation/profile_nav" />
    <include app:graph="@navigation/album_nav" />

    <action
        android:id="@+id/to_login_action"
        app:destination="@id/auth_nav"
        app:popUpTo="@id/auth_nav"
        app:popUpToInclusive="false" />

    <action
        android:id="@+id/to_albums_action"
        app:destination="@id/album_nav"
        app:popUpTo="@id/auth_nav" />

</navigation>

auth_nav.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/auth_nav"
    xmlns:tools="http://schemas.android.com/tools"
    app:startDestination="@+id/signin_dest">

    <fragment
        android:id="@+id/signin_dest"
        android:name="com.artemromanov.navigationplayground.ui.signin.SignInFragment"
        android:label="SignInFragment"
        tools:layout="@layout/fragment_sign_in">
    </fragment>
</navigation>

This is how I setup navigation in my MainActivity.kt inside onCreate()

  private fun setNavigation(startDestination: Int) {
    val navHostFragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
    navController = navHostFragment.navController

    val navController = navHostFragment.navController
    findViewById<BottomNavigationView>(R.id.bottom_navigator).setupWithNavController(navController)
    navController.addOnDestinationChangedListener { _, destination, _ ->
      Log.d("Activ", "${destination.id}, ${R.id.auth_nav}")

      when (destination.id) {
        R.id.signin_dest -> binding.bottomNavigator.visibility = View.GONE
        else -> binding.bottomNavigator.visibility = View.VISIBLE
      }
    }

    val navGraph = navController.navInflater.inflate(R.navigation.main_nav)
    navGraph.setStartDestination(startDestination)

    navController.graph = navGraph
  }

nav_menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/album_nav"
        android:title="Albums" />

    <item
        android:id="@+id/profile_nav"
        android:title="Profile" />
</menu>

Am I doing something wrong?

Answer 1

You just want a single instance of your fragment so when you are clicking albums inside the profile fragment you can just use the previous instance of albums.

Here, These answers will help you :

1. https://stackoverflow.com/a/24972247/14700539
2. https://stackoverflow.com/a/24972251/14700539