android – Jetpack导航：NavHostManager不是FragmentManager的活动片段

我正在使用jetpack Navigation来处理Fragments的导航.
我一直在关注文档并安装了所需的组件,当尝试显示托管NavHost片段的活动时,应用程序仍然崩溃

例外：

java.lang.IllegalArgumentexception: Fragment NavHostFragment{820022f} is not an active fragment of FragmentManager FragmentManager{5a5703c in HostCallBACks{a0b41c5}}
        at android.support.v4.app.FragmentManagerImpl.setPriMaryNavigationFragment(FragmentManager.java:3389)
        at android.support.v4.app.BACkStackRecord.executeOps(BACkStackRecord.java:783)
        at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2595)
        at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2382)
        at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2337)
        at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2244)

主要活动布局

<FrameLayout xmlns:android="http://scheR_178_11845@as.android.com/apk/res/android"
    xmlns:tools="http://scheR_178_11845@as.android.com/tools"
    xmlns:app="http://scheR_178_11845@as.android.com/apk/res-auto"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".LoginActivity" >

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

主要活动 – Kotlin

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceStatE)
        setContentView(R.layout.login_activity)
        if (savedInstanceState == null) {
            supportFragmentManager.begintransaction()
                    .replace(R.id.container,LoginFragment.newInstance())
                    .commitNow()
        }
    }

    override fun onSupportNavigateUp()
        = findNavController(R.id.my_nav_host_fragment).navigateUp()

}

我正在尝试测试jetPack的功能,而我目前仍然坚持这一点,任何人都有一个线索可能是错的？这是因为Android 3.2还在预览中吗？任何帮助将非常感激..

if (savedInstanceState == null) {
    supportFragmentManager.begintransaction()
            .replace(R.id.container,LoginFragment.newInstance())
            .commitNow()
}