如何处理Android嵌套片段中的导航图

Question

我正在片段中使用bottomNavigationView，并希望在每个选项上显示不同的片段。我可以看到BottomNavigationView，但我无法加载任何片段。我正在使用以下代码。

res/layout/fragment_main_tab.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"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">

<fragment
    android:id="@+id/nav_menu_fragment"
    android:name="androidx.navigation.fragment.NavHostFragment"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    app:defaultNavHost="true"
    app:layout_constraintBottom_toTopOf="@+id/bottom_navigation_view"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.5"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:navGraph="@navigation/main_menu_nav_graph" />

<com.google.android.material.bottomnavigation.BottomNavigationView
    android:id="@+id/bottom_navigation_view"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:itemBackground="@drawable/bottom_view_selector"
    app:labelVisibilityMode="labeled"
    app:layout_anchorGravity="bottom"
    app:layout_constraintBottom_toBottomOf="parent"
    app:menu="@menu/bottom_nav_menu"
    tools:ignore="MissingConstraints" />
</androidx.constraintlayout.widget.ConstraintLayout>

res/navigation/main_menu_nav_graph.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/main_menu_nav_graph"
app:startDestination="@id/navigation_main_tab_fragment">

<fragment
    android:id="@+id/navigation_main_tab_fragment"
    android:name="com.pkg.ui.main.MainTabFragment"
    android:label="@string/app_name"/>
</navigation>

code> maintabfragment.kt

 binding.bottomNavigationView.setOnItemSelectedListener {
        when (it.itemId) {
            R.id.home -> {
                findNavController().navigate(R.id.nav_menu_to_main_fragment)
            }
            R.id.wallet -> {
                findNavController().navigate(R.id.nav_menu_to_main_fragment)
            }
            else -> {
                null
            }
        }
        true
    }

res/navigation/navigation/navigation/navigation/nav_menu_graph.xml.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/nav_menu_graph"
app:startDestination="@id/nav_menu_to_main_fragment">
<fragment
    android:id="@+id/nav_menu_to_main_fragment"
    android:name="com.pkg.ui.main.MainFragment"
    android:label="@string/app_name" />
</navigation>

它总是显示空白，没有mainfragment或崩溃。有人可以检查一次并突出显示我是否犯错？提前致谢。

Answer 1

我认为您应该尝试此维护范围

(supportFragmentManager.findFragmentById(R.id.nav_menu_fragment) as NavHostFragment).navController.apply {
        binding.bnvAppBottomNav.setupWithNavController(this)
        addOnDestinationChangedListener { _, destination, _ ->
            binding.bnvAppBottomNav.visibility = when (destination.id) {
                R.id.Home,
                R.id.Wallet,
                R.id.Profile -> GONE

                else -> VISIBLE
            }
        }
    }

，也可以在res/layout/fragment_main_tab.xml中尝试一下

<androidx.fragment.app.FragmentContainerView
    android:id="@+id/nav_menu_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="0dp"
app:defaultNavHost="true"
app:layout_constraintBottom_toTopOf="@+id/bottom_navigation_view"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/main_menu_nav_graph" />

，希望这给您一些提示