Android导航体系结构组件-获取当前可见的片段

在尝试导航组件之前，我曾经手动执行片段事务，并使用fragment标签来获取当前片段.

Before trying the Navigation component I used to manually do fragment transactions and used the fragment tag in order to fetch the current fragment.

val fragment:MyFragment = supportFragmentManager.findFragmentByTag(tag):MyFragment

现在在我的主要活动布局中，我有类似的东西:

Now in my main activity layout I have something like:

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

如何通过导航"组件检索当前显示的片段?

How can I retrieve the current displayed fragment by the Navigation component? Doing

supportFragmentManager.findFragmentById(R.id.nav_host)

返回一个NavHostFragment，我想检索显示的'MyFragment`.

returns a NavHostFragment and I want to retrieve my shown 'MyFragment`.

谢谢.