HI Andrik, welcome!!!
Don´t care always it´s inahbilited... about the Parallel desktops, not it´s relevant.
If you want make your game to full screen you have to do this.
At the start of your code, before the loop put this.
//This its for fill the complete Screen
But if you put
You only wacth the rectagle, and your game into this rectangle whit the 480x320 dimensions.