使用嵌套片段时底部导航栏消失

我有一个Activity类，它的底部导航栏是3个（Home，Notification，Dashboard）片段，以及Home片段中还有1个片段（UpMenuFragment）。问题是，当我创建UpMenuFragment时，底部栏消失了

MainActivity.kt

    setContentView(R.layout.activity_main)

    val navView: BottomNavigationView = findViewById(R.id.nav_view)

    val navController = findNavController(R.id.nav_host_fragment)
    val appBarConfiguration = AppBarConfiguration(
        setOf(
            R.id.navigation_home, R.id.navigation_dashboard, R.id.navigation_notifications
        )
    )
    setupActionBarWithNavController(navController, appBarConfiguration)
    navView.setupWithNavController(navController)

activity_main.xml

    <?xml version="1.0" encoding="utf-8"?>
    <androidx.constraintlayout.widget.ConstraintLayout android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:paddingTop="?attr/actionBarSize"
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto">

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

        <androidx.constraintlayout.widget.ConstraintLayout
            android:id="@+id/main_container"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_constraintBottom_toTopOf="@id/nav_view"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

            <fragment
            android:id="@+id/nav_host_fragment"
            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>

HomeFragment.kt

    val upMenuFragment = UpMenuFragment.newInstance()
    childFragmentManager.beginTransaction().add(R.id.home_up_menu_container, 
    upMenuFragment).commit()

fragment_home.xml

         <?xml version="1.0" encoding="utf-8"?>

         <androidx.constraintlayout.widget.ConstraintLayout
          xmlns:android="http://schemas.android.com/apk/res/android"
          xmlns:app="http://schemas.android.com/apk/res-auto"
          android:layout_width="match_parent"
          android:layout_height="match_parent">

        <androidx.constraintlayout.widget.ConstraintLayout
            android:id="@+id/home_up_menu_container"
            android:layout_width="match_parent"
            android:layout_height="300dp"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />
       </androidx.constraintlayout.widget.ConstraintLayout>

所以有什么问题？