Android导航架构组件：使用NavigationView的BackStack错误

我正在使用Android Navigation Architecture Components来导航基于片段的单活动应用程序 . 主导航是通过NavigationDrawer-pattern实现的：带有NavigationView和NavHostFragment plus的DrawerLayout以及其他工具栏 .

到目前为止一切正常 - 我能够导航到每个片段 - 除了主级片段的BackStack . 似乎将除startStest之外的任何片段添加到BackStack而不是像常规NavigationDrawer那样被替换 .

可以通过Burger-icon识别错误行为，当我导航到除startDestination之外的片段时，该图标会切换到Back-icon，并导航回导致startDestination而不是退出应用程序 .

如何使用导航架构组件以与NavigationView结合替换主要碎片？

我正在初始化导航架构组件，如下所示：

class MainActivity : AppCompatActivity {

    private val navigationHostFragment: NavHostFragment
        get() = supportFragmentManager.findFragmentById(R.id.navigationHost) as NavHostFragment

    private val navigationController: NavController
        get() = navigationHostFragment.navController

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity)

        // Views are bound via Kotlin Android Extensions
        setSupportActionBar(toolbar)
        NavigationUI.setupWithNavController(toolbar, navigationController, drawerLayout)
        NavigationUI.setupWithNavController(navigationView, navigationController)
    }

    override fun onSupportNavigateUp(): Boolean = findNavController(R.id.navigationHost).navigateUp()
}

活动的布局（/res/layout/activity.xml）如下所示：

<androidx.drawerlayout.widget.DrawerLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/drawerLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"/>

        <fragment
            android:id="@+id/navigationHost"
            android:name="androidx.navigation.fragment.NavHostFragment"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:navGraph="@navigation/navigation"
            app:defaultNavHost="true"/>

    </LinearLayout>

    <com.google.android.material.navigation.NavigationView
        android:id="@+id/navigationView"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        app:menu="@menu/navigation"/>

</androidx.drawerlayout.widget.DrawerLayout>

导航图（/res/navigation/navigation.xml）如下所示：

<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"
    app:startDestination="@id/first">

    <fragment
        android:id="@+id/first"
        android:name="de.example.FirstFragment"
        android:label="@string/first"/>

    <fragment
        android:id="@+id/second"
        android:name="de.example.SecondFragment"
        android:label="@string/second"/>

</navigation>

NavigationView（/res/menu/navigation.xml）的菜单如下所示：

<menu xmlns:android="http://schemas.android.com/apk/res/android">

    <group android:checkableBehavior="single">

        <item
            android:id="@+id/first"
            android:title="@string/first"/>

        <item
            android:id="@+id/second"
            android:title="@string/second"/>

    </group>

</menu>

相关的依赖项如下所示：

dependencies {
    implementation 'com.google.android.material:material:1.0.0'
    implementation 'androidx.core:core-ktx:1.0.0'
    implementation 'android.arch.navigation:navigation-fragment-ktx:1.0.0-alpha06'
    implementation 'android.arch.navigation:navigation-ui-ktx:1.0.0-alpha06'
}