android toolbar popupTheme vs theme

Question

Often I see this declaration of Toolbar in layout files:

<android.support.v7.widget.Toolbar     xmlns:android="http://schemas.android.com/apk/res/android"     android:layout_width="match_parent"     android:layout_height="?attr/actionBarSize"     app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"     app:popupTheme="@style/ThemeOverlay.AppCompat.Light"> </android.support.v7.widget.Toolbar> 

Why are there two attributes relating theming: theme and popupTheme?

What are the purposes of each of them?

Answer 1

1. popupTheme

   Specifies the theme to use when inflating popup menus. By default, uses the same theme as the Toolbar itself.

2. theme

   It is simply the theme of Toolbar.