If Hamlet confessed that he does not love Ophelia once, then why does he talk to her during the play and seem like he is flirting with her?

Well i dont really agree with gbeatty i dont belive that Hamlet is acting crazy. That might have been his intention at first but the madness took over him. Just imagine if you were him and you were depressed, contemplating suicide, your father died, you just saw his ghost, and it was your uncle that killed him. He was pushed over the edge.

I do belive that he does love Ophelia. It is mentioned that they were in a relationship prior to his madness. And in the letters that he wrote to Ophelia show a deep love for her. I think that he is fighting with himself to try and not to love her, because he saw his mother marry his uncle so quickly after the death of his father. He says "frailty thy name is women".

    If it wasn't for outside influences they would be happily together still. Ophelia loves Hamlet also but has to be loyal to her father and brother and distance himself from him. And also Hamlet confesses his love for Ophelia in the burial scene.  It can be interpreted anyway you want really, thats what makes this story so great.