navgraph的id将生成/使用哪个类或属性？哪个班级将使用它？例如，android studio将使用哪个类“nav2”？

<?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/nav2"
    app:startDestination="@id/forthFragment">

    <fragment
        android:id="@+id/forthFragment"
        android:name="com.ui.main.UiFragmentA"
        android:label="fragment_forth"
        tools:layout="@layout/fragment_forth" >
    </fragment>

</navigation>