FB logon appearing behind Acitivity screen

I am trying to logon to FB from within an activity. For some reason the开发者_如何学Go FB logon screen appears behind the activity screen.

The activity theme is defined as "android:theme="@android:style/Theme.Dialog" because I want it to look like a dialog.

This is what I am getting:

I tried changing my activity not to be theme dialog but didn't help.