why does the chronology of the child view in navigationdrawer matters?

Question

I ran into this issue while developing a navigation drawer for my app,when the chronology of the child views are as follows everything works like a charm

    <androidx.drawerlayout.widget.DrawerLayout
        android:id="@+id/drawer_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:openDrawer="start">

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

        <com.google.android.material.navigation.NavigationView
            android:id="@+id/nav_view"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_gravity="start"
            app:headerLayout="@layout/nav_header"
            app:menu="@menu/nav_menu" />
    </androidx.drawerlayout.widget.DrawerLayout>

and the menu items stop responding to the clicks if the child views are as follows

    <androidx.drawerlayout.widget.DrawerLayout
        android:id="@+id/drawer_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:openDrawer="start">

        <com.google.android.material.navigation.NavigationView
            android:id="@+id/nav_view"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_gravity="start"
            app:headerLayout="@layout/nav_header"
            app:menu="@menu/nav_menu" />

        <fragment
            android:id="@+id/nav_host_fragment"
            android:name="androidx.navigation.fragment.NavHostFragment"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:defaultNavHost="true"
            app:navGraph="@navigation/main_nav_graph" />
    </androidx.drawerlayout.widget.DrawerLayout>

So thereby the chronology of the child views inside the navigation drawer matters, I wanna know why?

Answer 1

In the documentation for DrawerLayout it says this:

To use a DrawerLayout, position your primary content view as the first child with width and height of match_parent and no layout_gravity>. Add drawers as child views after the main content view and set the layout_gravity appropriately. Drawers commonly use match_parent for height with a fixed width.

Documentation source: DrawerLayout

So my guess for this is that content needs to be the first child because the menu is sliding over your content. It is probably in the background on how DrawerLayout handles these layouts. So if you put it as a second child it will somehow overlap and disable click events on the menu itself. Hope this explains it.