Creating IDs under res/xml

Part of res/xml/prompts.xml:


<card
    id="+@id/amytis"
    title="Amytis"
    players="L"
    type="Amytis"
    cost="4" />

Then in the code:


String id = xml.getAttributeValue(null, "id");

I get "+@id/amytis" verbatim. I expected to get an integer -- an automatically created ID. What am I doing wrong?