Exploring the autogenerated code and assets

Open the res/menu folder. Notice there is an extra file titled activity_main_drawer.xml. This next code is an excerpt from this file, so we can discuss its contents:

<group android:checkableBehavior="single">
     <item
          android:id="@+id/nav_home"
          android:icon="@drawable/ic_menu_camera"
          android:title="@string/menu_home" />
     <item
          android:id="@+id/nav_gallery"
          android:icon="@drawable/ic_menu_gallery"
          android:title="@string/menu_gallery" />
 ...