Summarize before and after the soliloquy in act 2, scene 2 of Hamlet.

In act 2, scene 2 Hamlet's old school friends, Rosencrantz and Guildenstern, have been instructed by Claudius to spy on him. Hamlet is no fool, however, and suspects the reason for their presence at court. So he's going to play along with them, giving his old friends the impression that he's psychologically disturbed. He launches into a monologue, which includes the lines "I have of late—but wherefore I know not—lost all my mirth." In other words, Hamlet has become quite sad lately, and he doesn't know why. Hamlet knows that Rosencrantz and Guildenstern will faithfully report every word of his lament back to Claudius and Gertrude, so he's keen to play up his depression and general despondency.
After Hamlet has finished his monologue, Rosencrantz tells him of the company of actors he's just passed on the way to Elsinore. If it's true, as Hamlet says in his monologue, that people no longer interest him, then Rosencrantz doesn't see how he will be entertained by the actors when they arrive. But of course Hamlet's purpose in hiring the drama company is nothing to do with entertainment; he's going to stage a play to watch Claudius squirm, so as to obtain proof of what the Ghost tells him about Claudius's murdering Hamlet's father.