mihon/app/src/main/res/menu/library.xml

<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=".MainActivity">

    <item
        android:id="@+id/action_filter"
        android:title="@string/action_filter"
        android:icon="@drawable/ic_filter_list"
        app:showAsAction="ifRoom">
        <menu>
            <item
                android:id="@+id/action_filter_downloaded"
                android:checkable="true"
                android:title="@string/action_filter_downloaded"/>
            <item
                android:id="@+id/action_filter_unread"
                android:checkable="true"
                android:title="@string/action_filter_unread"/>
            <item
                android:id="@+id/action_filter_empty"
                android:title="@string/action_filter_empty"/>
        </menu>
    </item>

    <item
        android:id="@+id/action_search"
        android:title="@string/action_search"
        android:icon="@drawable/ic_search_white_24dp"
        app:showAsAction="collapseActionView|ifRoom"
        app:actionViewClass="android.support.v7.widget.SearchView" />

    <item
        android:id="@+id/action_refresh"
        android:title="@string/action_refresh"
        android:icon="@drawable/ic_refresh_white_24dp"
        app:showAsAction="ifRoom" />

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

</menu>