关于"I don't have no idea."

问题描述:

关于"I don't have no idea."
那次看电影,听见一个人说"I don't have no idea.",字幕是"我不知道".
不应该是"I have no idea.
难道是我把"I do"听成""I don't"了?

两个都没有错,在口语中很多时候人们用双重否定表示否定.
eg.i ain't got nothing