Since when did any game you ever played written in even the most powerful languages and 2d/3d api's ever display a popup during the programs run in fullscreen exclusive mode? (Error popup dialogs that end the game dont count. Unless you 'wanted' your app to end after a popup of course... o_O)
Now, as for a more efficient/robust/intuitive/cooler etc way to display important information to the user, perhaps your game (I'm assuming its a game due to where this is posted) should draw its own frame lookalike that could function just like a popup, only it resided in the game, and had its own look and feel. ( a look that should undoubtly be way more apealing to your audience than a standard dialog...)
I am thinking he doesnt acutally want a 'popup' as much as a rectangluar shape with text and things in it that sits on top of his main image. Like a right mouse click give you a command menu in some games that 'floats' above the game.
Try painting a solid rectangle at the end of your paint loop. witha boolean check. If true, paint me.
That is exactly what I was thinking however, it's more
than just a message 'image' painted over everything else: It will have to be interactive ie: one popup is a picture of an open backpack with the items inside it. I will have to be able to drag the items around. I'm sure it's possible that way but it makes things horribly complicated when I could just use swing/awt in a popup.
if u realy wanted to use awt/swing components, you could manually pass the graphics context of your fullscreen frame into the paint(Graphics method) of the awt/swing component that you wanted rendering.
That would get you your desired output (more or less), but awt/swing arn't reknown for their efficiency... (and the overhead of an awt/swing omponent is far greater than would be otherwise necessary)