Make spinners show a bottom line and a down arrow easily.

styles.xml

<resources>
    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <item name="android:spinnerStyle">@style/AppTheme.Form.Spinner</item>
        <item name="android:spinnerItemStyle">@style/AppTheme.Form.Spinner.Item</item>
    </style>

    <!-- Spinner Styles -->
    <style name="AppTheme.Form.Spinner" parent="Widget.AppCompat.Spinner">
        <item name="android:paddingRight">0dp</item>
        <item name="android:paddingEnd">0dp</item>
    </style>
    <style name="AppTheme.Form.Spinner.Item" parent="Widget.AppCompat.EditText">
        <item name="android:clickable">false</item>
    </style>
</resources>

This mimics the look that the Google Contacts app shows.