kotlin - Android Navigation graph with Bottom Navigation view not working properly - Stack Overflow

admin管理员组

文章数量:1419168

I have a MainActivity with a navigation graph which has two fragments say FragmentA and FragmentBottomNav. When click on a button in FragmentA the app navigates from FragmentA to FragmentBottomNav.

The FragmentBottomNav contains a BottomNavigationView and it has a separate navigation graph with 2 fragments FragmentB and FragmentC.

Everything works fine util this.When I press back button from FragmentBottomNav fragment it navigates back to FragmentA, but when I navigate to FragmentBottomNav again from FragmentA, The FragmentB and FragmentC are not loading.

Please find the Navigation graph and code snippets below.

main_navigation_graph.xml

<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android=";
    xmlns:app=";
    xmlns:tools=";
    android:id="@+id/nav_test"
    app:startDestination="@id/fragmentA">

    <fragment
        android:id="@+id/fragmentA"
        android:name="com.test.presentation.test.FragmentA"
        android:label="FragmentA"
        tools:layout="@layout/fragment_a">
        <action
            android:id="@+id/action_fragmentA_to_BNavTestFragment"
            app:destination="@id/BNavTestFragment" />
    </fragment>
    <fragment
        android:id="@+id/BNavTestFragment"
        android:name="com.test.presentation.test.BottomNavTestFragment"
        android:label="BNavTestFragment"
        tools:layout="@layout/fragment_b_nav_test" />
</navigation>

bottom_nav_graph.xml

<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android=";
    xmlns:app=";
    xmlns:tools=";
    android:id="@+id/nav_test_bottom"
    app:startDestination="@id/orderFragment">

    <fragment
        android:id="@+id/orderFragment"
        android:name="com.test.presentation.test.FragmentB"
        android:label="FragmentB"
        tools:layout="@layout/fragment_b" />

    <fragment
        android:id="@+id/profileFragment"
        android:name="com.test.presentation.test.FragmentC"
        android:label="FragmentC"
        tools:layout="@layout/fragment_c" />


</navigation>

fragment_layout_of_bottom_navigation.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android=";
    xmlns:app=";
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#E0668F">


    <!-- Fragment Container for Navigation -->
    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/nav_host_member_bottom_nav"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:defaultNavHost="true"
        app:layout_constraintBottom_toTopOf="@+id/bottom_navigation"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:navGraph="@navigation/nav_test_bottom_view" />


    <!-- BottomNavigationView -->
    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/bottom_navigation"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom"
        app:backgroundTint="@color/primary_variant"
        app:itemIconTint="@color/bottom_nav_item_color"
        app:itemTextColor="@color/bottom_nav_item_text_color"
        app:labelVisibilityMode="labeled"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:menu="@menu/bottom_nav_menu_test" />

</androidx.constraintlayout.widget.ConstraintLayout>


menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android=";>

    <item
        android:id="@+id/orderFragment"
        android:icon="@drawable/ic_bottom_menu_orders"
        android:title="@string/bt_menu_orders" />
    <item
        android:id="@+id/profileFragment"
        android:icon="@drawable/ic_bottom_menu_profile"
        android:title="@string/bt_menu_profile" />

</menu>


//inside BottomNavFragment.kt
    private fun setUpBottomNavigation() {
        val navHostFragment = requireActivity().supportFragmentManager
            .findFragmentById(R.id.nav_host_member_bottom_nav) as NavHostFragment
        val navController: NavController = navHostFragment.navController


        val bottomNavigationView =
            requireView().findViewById<BottomNavigationView>(R.id.bottom_navigation)
        bottomNavigationView.setupWithNavController(navController)
    }

I have a MainActivity with a navigation graph which has two fragments say FragmentA and FragmentBottomNav. When click on a button in FragmentA the app navigates from FragmentA to FragmentBottomNav.

The FragmentBottomNav contains a BottomNavigationView and it has a separate navigation graph with 2 fragments FragmentB and FragmentC.

Everything works fine util this.When I press back button from FragmentBottomNav fragment it navigates back to FragmentA, but when I navigate to FragmentBottomNav again from FragmentA, The FragmentB and FragmentC are not loading.

Please find the Navigation graph and code snippets below.

main_navigation_graph.xml

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

    <fragment
        android:id="@+id/fragmentA"
        android:name="com.test.presentation.test.FragmentA"
        android:label="FragmentA"
        tools:layout="@layout/fragment_a">
        <action
            android:id="@+id/action_fragmentA_to_BNavTestFragment"
            app:destination="@id/BNavTestFragment" />
    </fragment>
    <fragment
        android:id="@+id/BNavTestFragment"
        android:name="com.test.presentation.test.BottomNavTestFragment"
        android:label="BNavTestFragment"
        tools:layout="@layout/fragment_b_nav_test" />
</navigation>

bottom_nav_graph.xml

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

    <fragment
        android:id="@+id/orderFragment"
        android:name="com.test.presentation.test.FragmentB"
        android:label="FragmentB"
        tools:layout="@layout/fragment_b" />

    <fragment
        android:id="@+id/profileFragment"
        android:name="com.test.presentation.test.FragmentC"
        android:label="FragmentC"
        tools:layout="@layout/fragment_c" />


</navigation>

fragment_layout_of_bottom_navigation.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android/apk/res/android"
    xmlns:app="http://schemas.android/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#E0668F">


    <!-- Fragment Container for Navigation -->
    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/nav_host_member_bottom_nav"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:defaultNavHost="true"
        app:layout_constraintBottom_toTopOf="@+id/bottom_navigation"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:navGraph="@navigation/nav_test_bottom_view" />


    <!-- BottomNavigationView -->
    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/bottom_navigation"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom"
        app:backgroundTint="@color/primary_variant"
        app:itemIconTint="@color/bottom_nav_item_color"
        app:itemTextColor="@color/bottom_nav_item_text_color"
        app:labelVisibilityMode="labeled"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:menu="@menu/bottom_nav_menu_test" />

</androidx.constraintlayout.widget.ConstraintLayout>


menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android/apk/res/android">

    <item
        android:id="@+id/orderFragment"
        android:icon="@drawable/ic_bottom_menu_orders"
        android:title="@string/bt_menu_orders" />
    <item
        android:id="@+id/profileFragment"
        android:icon="@drawable/ic_bottom_menu_profile"
        android:title="@string/bt_menu_profile" />

</menu>


//inside BottomNavFragment.kt
    private fun setUpBottomNavigation() {
        val navHostFragment = requireActivity().supportFragmentManager
            .findFragmentById(R.id.nav_host_member_bottom_nav) as NavHostFragment
        val navController: NavController = navHostFragment.navController


        val bottomNavigationView =
            requireView().findViewById<BottomNavigationView>(R.id.bottom_navigation)
        bottomNavigationView.setupWithNavController(navController)
    }

• android
• kotlin
• navigation
• bottomnavigationview
• android-navigation-graph

Share Improve this question Follow edited Jan 29 at 8:10 darwin asked Jan 29 at 7:56 darwindarwin 1,59411 gold badge2323 silver badges3333 bronze badges

Add a comment  | 

1 Answer 1

Sorted by: Reset to default 0

when navigating back to FragmentBottomNav from FragmentA, you need to ensure that the BottomNavigationView and its associated navigation graph are properly re-initialized when FragmentBottomNav is reloaded.

class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)

    val navController = findNavController(R.id.nav_host_fragment)
    setupActionBarWithNavController(navController)
}

override fun onSupportNavigateUp(): Boolean {
    val navController = findNavController(R.id.nav_host_fragment)
    return navController.navigateUp() || super.onSupportNavigateUp()
 }
}

Fragment

class FragmentBottomNav : Fragment(R.layout.fragment_bottom_nav) {

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)

    val navHostFragment = childFragmentManager.findFragmentById(R.id.bottom_nav_host_fragment) as NavHostFragment
    val navController = navHostFragment.navController

    val bottomNavigationView = view.findViewById<BottomNavigationView>(R.id.bottom_navigation_view)
    bottomNavigationView.setupWithNavController(navController)
 }
}

And we also have OnNavigationItemReselectedListener to handle reselection,so can also be managed by this

bottomNavigationView.setOnNavigationItemReselectedListener { item ->
when (item.itemId) {
    R.id.fragmentB -> {
        // Handle reselection of FragmentB
        // For example, refresh the fragment
        val navHostFragment = childFragmentManager.findFragmentById(R.id.bottom_nav_host_fragment) as NavHostFragment
        val navController = navHostFragment.navController
        navController.popBackStack(R.id.fragmentB, false)
        navController.navigate(R.id.fragmentB)
    }
    R.id.fragmentC -> {
        // Handle reselection of FragmentC
        // For example, refresh the fragment
        val navHostFragment = childFragmentManager.findFragmentById(R.id.bottom_nav_host_fragment) as NavHostFragment
        // or you can refresh here or make it start destination and pop back fragment, your call
    }
 }
}

本文标签： kotlinAndroid Navigation graph with Bottom Navigation view not working properlyStack Overflow