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

You should use action layout

<menu 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"
    tools:context=".LandingActivity">
    <item
        android:id="@+id/action_cart"
        android:title="cart"
        android:actionLayout="@layout/cart_update_count"
        android:icon="@drawable/shape_notification"
        app:showAsAction="always"/>
</menu>

and then the action layout can have the textview with divider.

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <View
        android:id="@+id/divider"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@drawable/divider"/>

    <TextView
        android:id="@android:id/text"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="?android:attr/selectableItemBackground"
        android:gravity="center_vertical"          
        android:textAppearance="?attr/textAppearanceListItemSmall"/>

</LinearLayout>

then you can add the click listener in code