People should try to sense when someone wants to get left alone and leave them alone. I don't know how much you communicate that and misunderstandings do happen. Anyway regardless of whether someone just doesn't get that you don't feel like talking or whether they do not care, when just giving short direct answers to questions that only maintain the minimum level of friendliness does not work to get someone to stop talking to you you are doing both of you a favor by directly, but politely telling them that you do not feel like talking right now.