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.