How to add dividers between specific menu items?

Question

Background

I have a menu item in the action bar (toolbar actually) that when clicked, shows a list of items to choose from, similar to radio-buttons:

<menu xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto">

    <item
        android:icon="@drawable/..."
        android:title="@string/..."
        app:showAsAction="always">
        <menu>
            <group
                android:id="@+id/..."
                android:checkableBehavior="single">
                <item .../>
                <item .../>
                <item .../>
            </group>
        </menu>
    </item>
</menu>

I need to put an item below this list of items, that will have a divider between it and the list. Similar to what the material design guidelines show (taken from here) :

EDIT: here's a sketch of what I want to do:

The problem

I can't find a way to do it.

What I've tried

The only possible solutions I've found are:

1. change the theme of the activity (here), but this will also affect other menu items of the activity

2. methods to put a divider between menu items when they appear on the action bar, but here they do not appear on the toolbar itself. They appear on a popup menu of a selected item.

3. I tried to put fake items between the list and the extra item, and I also tried to put a group, an empty group and even tried various attributes.

Sadly nothing worked.

The question

How can I add a divider between specific items of an action-item's popup menu ?

Perhaps I need to create a custom popup menu when clicking on the action item (like here) ? If so, how do I put a divider between specific items there ? Maybe use a Spinner as an action item?

Answer 1

In Material3 Design, MDC-Android, make menu items in each group, and call setGroupDividerEnabled(Boolean).

Dividers will inserted between group or menu item(s).

MyActivity.kt

private val binding by lazy { ActivityMyBinding.inflate(layoutInflater) }

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(binding.root)
     
    // other initializations..
    // ...

    binding.toolbar.menu.setGroupDividerEnabled(true)
}

activity_my.xml

<androidx.coordinatorlayout.widget.CoordinatorLayout 
    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:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.google.android.material.appbar.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <com.google.android.material.appbar.MaterialToolbar
            <!-- Other properties -->
            android:id="@+id/toolbar"
            app:menu="@menu/main" />

    </com.google.android.material.appbar.AppBarLayout>

</androidx.coordinatorlayout.widget.CoordinatorLayout>

menu.xml

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <item
        android:id="@+id/item0"
        android:title="item0"
        app:showAsAction="never" />


    <item
        android:id="@+id/item1"
        android:title="item1"
        app:showAsAction="never" />

    <group android:id="@+id/group0">
        <item
            android:id="@+id/item2"
            android:title="group0 item2"
            app:showAsAction="never" />
    </group>

    <group android:id="@+id/group1">
        <item
            android:id="@+id/item3"
            android:title="group1 item3"
            app:showAsAction="never" />

        <item
            android:id="@+id/item4"
            android:title="group1 item4"
            app:showAsAction="never" />
    </group>

</menu>