I'm looking for a document to confirm if Jabber for Android can ring while the phone is locked but only can find that for iOS
No such limitation / restriction is giving in the release notes in the below link.
So this feature is expected to work. Please let me know if this is fine enough.
sorry for being inaccurate, the behavior is that IPhones can't pickup the calls while it is locked. we tried that using jabber 11.7. when we unlock the phone by "slide to unlock" the call is ignored.