Whether to order the Preference under this group as they appear in the XML file. If this is false, the ordering will follow the Preference order attribute and default to alphabetic for those without the order attribute.

Must be a boolean value, either "true" or "false".

This may also be a reference to a resource (in the form "@[package:]type:name") or theme attribute (in the form "?[package:][type:]name") containing a value of this type.

[Android Documentation]