Such a loaded question! For some reason, my mind spun your question in a completely different way (so much so that I actually laughed when I read it). My first thought was, "People have been fighting about this since it was written, . . . and they still don't know the answer!" Namely, what exactly is Hamlet's state of mind after he says this:
As I perchance hereafter shall think meet / To put an antic disposition on. (1.5.171-172)
True, this is said far before Act 3, Scene 2, but it is important because some critics argue that, from that point on, Hamlet doesn't just act crazy, he actually goes crazy. This arguement is expecially significant because in the scene previous to the one you mention, Hamlet says this:
Go to, I'll no more on't; it hath made me mad, I say we will have no moe marriage. (3.1.148-150)
Mad in truth, or mad in jest?
To further the inquiry, at the beginning of Scene 2, Hamlet says some things to Ophelia that are quite unbecoming of a gentleman: things like "Lady, shall I lie in your lap?" while he shows signs of nervous tension like you've never seen. On the other side is the idea that Hamlet is obviously "acting" a bit nuts here, and his nervous tension is the result of the knowledge of The Murder of Gonzago plot: a plot that will surely reveal the truth behind Claudius' actions.
Therefore I must concur with the first answerer, the reader/watcher must infer Hamlet's state of mind; however, we may never know exactly how Shakespeare wanted us to feel about it because, luckily, this scene can be acted in completely different ways. Thus, the bard and playwright of the Elizabethan Age keeps things interesting for us centuries and centuries later!