我有一个应用程序，其中使用NavigationComponents与ViewPager 2。
我想使用ViewPager在片段之间切换。我已经把我的ActivityMain设置为FragmentContainerView，并且我想在我的一个片段中实现ViewPager。
问题是，ViewPager根本不起作用。它不改变片段，不知道为什么。我应该在代码中改变什么？
主要活动

<?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"
    tools:context=".MainActivity">
    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/fragmentContainerView"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true"
        app:navGraph="@navigation/nav_graph" />
</androidx.constraintlayout.widget.ConstraintLayout>

第一个片段

class BlankFragment : Fragment() {
    private var mPag: ViewPager2? = null

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.fragment_blank, container, false)
    }

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

        mPag = view.findViewById(R.id.pager123)
        val adapter = PagerAdapter(this)
        val list = mutableListOf<Fragment>()
        list.add(BlankFragment())
        list.add(BlankFragment2())
        mPag?.adapter = adapter
    }
}

.xml文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".BlankFragment"
    android:orientation="vertical">
    <TextView
        android:id="@+id/test123"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="111111111" />

    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/pager123"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#a1a1"/>
</LinearLayout>

第二个片段

class BlankFragment2 : Fragment() {

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

    }
    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_blank2, container, false)
    }
}

.xml文件

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".BlankFragment2">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="222222222222222" />

</FrameLayout>

导航图

<?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"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/nav_graph"
    app:startDestination="@id/blankFragment">

    <fragment
        android:id="@+id/blankFragment"
        android:name="com.example.myapplication.BlankFragment"
        android:label="fragment_blank"
        tools:layout="@layout/fragment_blank" />
    <fragment
        android:id="@+id/blankFragment2"
        android:name="com.example.myapplication.BlankFragment2"
        android:label="fragment_blank2"
        tools:layout="@layout/fragment_blank2" />
</navigation>

寻呼机适配器

class PagerAdapter(fragment: Fragment) : FragmentStateAdapter(fragment) {
    val mFragments = mutableListOf<Fragment>()
    
    override fun getItemCount(): Int {
        return mFragments.size
    }

    override fun createFragment(position: Int): Fragment {
        when (position){
            0 -> return BlankFragment()
            1 -> return BlankFragment2()
        }
        return mFragments[position]
    }
}