How to add line divider for menu item Android

Make sure to call MenuCompat.setGroupDividerEnabled(menu, true); when you inflate your menu, otherwise groups will not be separated by divider!

Example:

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu_activity_main, menu);

    MenuCompat.setGroupDividerEnabled(menu, true);

    return true;
}

And make sure to have different groups in your menu xml, e.g.:

    <menu>
        <group android:id="@+id/sorting" >
            <item
                android:id="@+id/action_sorting_new_old"
                android:title="@string/action_sorting_new_old"/>

            <item
                android:id="@+id/action_sorting_a_z"
                android:title="@string/action_sorting_a_z"/>
        </group>

        <group android:id="@+id/settings">
            <item
                android:id="@+id/action_settings"
                android:title="@string/action_settings"/>
        </group>
    </menu>