Once in the Three Kingdoms Period (220-280), the duke of the Wei, Cao Rui, planed to select a very capable man to work for him. He said to his ministers: 'When choosing a talented person, always beware of one with a false reputation. A false reputation is just like a picture of a cake; it can' t ease hunger.'
Later, this idiom came to be used to mean comforting oneself with unrealistic thoughts, without solving practical problems.

三国时代魏国的皇帝曹睿，准备选拔一个有才能的人到朝廷来做关。曹睿兑他的大臣说：“选择人才，不能光找有虚名的人。虚名好像是画的一块饼，只能看，不能解决肚子饥饿的问题啊！”
后来人们就用“画饼充饥”这个成语比喻用空想安慰自己，不能解决实际问题。