android - 如何隐藏底部栏导航。当遵循单一 Activity 设计时？

Question

我试图仅在几个 fragment 中显示底部栏导航(即隐藏我的大部 fragment 段)..

我阅读了 official document关于这个，但我不清楚，比如我把代码放在哪里，我读了comments on this here on StackOverFlow ，例如“我很惊讶文档中建议这样做，因为它实际上看起来很糟糕，因为监听器在新 fragment 放置在屏幕上之前触发，导致可见闪烁(有时存在，有时不存在)”。

我对此进行了研究，据我了解，我需要创建一个嵌套的 naviagtion_graph(导航)或其他东西，听 onDestinationChanged 并将底部导航或工具栏设置为 Gone..

我不太明白这个..我只是想在大多数 fragment 中隐藏底部栏导航..

这是我的 navigation_gragh (mobile_navigation):

<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/mobile_navigation"
    app:startDestination="@+id/navigation_home">

    <fragment
        android:id="@+id/navigation_home"
        android:name="com.example.testingbottomnav.ui.home.HomeFragment"
        android:label="@string/title_home"
        tools:layout="@layout/fragment_home" >
        <action
            android:id="@+id/action_navigation_home_to_newScreenFragment"
            app:destination="@id/newScreenFragment" />
    </fragment>

    <fragment
        android:id="@+id/navigation_dashboard"
        android:name="com.example.testingbottomnav.ui.dashboard.DashboardFragment"
        android:label="@string/title_dashboard"
        tools:layout="@layout/fragment_dashboard" />

    <fragment
        android:id="@+id/navigation_notifications"
        android:name="com.example.testingbottomnav.ui.notifications.NotificationsFragment"
        android:label="@string/title_notifications"
        tools:layout="@layout/fragment_notifications" />
    <fragment
        android:id="@+id/newScreenFragment"
        android:name="com.example.testingbottomnav.ui.newscreen.NewScreenFragment"
        android:label="fragment_new_screen"
        tools:layout="@layout/fragment_new_screen" />
</navigation>

这是我的 activity_main.xml :

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

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

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

这是我的 MainActivty.kt :

class MainActivity : AppCompatActivity() {

    private lateinit var binding: ActivityMainBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        val navView: BottomNavigationView = binding.navView

        val navController = findNavController(R.id.nav_host_fragment_activity_main)
        // Passing each menu ID as a set of Ids because each
        // menu should be considered as top level destinations.
        val appBarConfiguration = AppBarConfiguration(
            setOf(
                R.id.navigation_home, R.id.navigation_dashboard, R.id.navigation_notifications
            )
        )
        setupActionBarWithNavController(navController, appBarConfiguration)
        navView.setupWithNavController(navController)
    }
}

任何帮助将不胜感激，谢谢..

Answer 1

如果您想让 BottomNavigationView 仅在目的地是顶级目的地时可见，您可以尝试:

 val appBarConfiguration = AppBarConfiguration(
            setOf(
                R.id.navigation_home, 
                R.id.navigation_dashboard, 
                R.id.navigation_notifications
            )
        )
 navController.addOnDestinationChangedListener { controller: NavController, destination: NavDestination, bundle: Bundle? ->
 yourBottomNavigationView.isVisible = appBarConfiguration.topLevelDestinations.contains(destination.id)
}