1 将来完成进行时的用法：想像未来的某个时间点，并谈论一直到该时间点仍在持续进行的动作。 

At the start of the next scene, I will have been eating noodles for five minutes.

By this Thursday, he will have been waiting for this parcel for 20 days.

2 将来完成进行时的基本结构：主语 + will have been + 动词-ing。可以把其中的 “will” 改为 “won't” 来组成将来完成进行时的否定句。 

At lunchtime, I will have been working for four hours.

My colleagues are getting a pay rise next week, but I won't have been working here for long enough to receive it.