to put up a bluff to conceal one's weakness, based on the classic 'Empty City Stratagem'

对方其实已经没有后援了，只是在唱空城计。

to have a rumbling or empty stomach

忙了一上午，我的肚子正唱空城计呢。

to be deserted or empty of people (referring to a house, room, or office)

大家都出去旅游了，家里正唱空城计呢。