demo code

gistfile1.txt

# skins.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
    <item type="skin" name="foo">10</item>
</resources>

# attrs.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="Skin">
        <attr name="skin" format="enum">
            <enum name="white" value="0" />
            <enum name="green" value="1" />
        </attr>
    </declare-styleable>
</resources>