How to get an attribute from an XMLReader

I have some HTML that I'm converting to a Spanned using Html.fromHtml(...), and I have a custom tag that I'm using in it:

<customtag id="1234">

So I've implemented a TagHandler to handle this custom tag, like so:

public void handleTag( boolean opening, String tag, Editable output, XMLReader xmlReader ) {

    if ( tag.equalsIgnoreCase( "customtag" ) ) {

        String id = xmlReader.getProperty( "id" ).toString();
    }
}

In this case I get a SAX exception, as I believe the "id" field is actually an attribute, not a property. However, there isn't a getAttribute() method for XMLReader. So my question is, how do I get the value of the "id" field using this XMLReader? Thanks.