将来完成时概念：

将来完成时用来表示在将来某一时间以前已经完成或一直持续的动作。经常与before+将来时间或by+将来时间连用，也可与before或by the time引导的现在时的从句连用。

将来完成时的构成与用法：

（一）构成：will/shall have+过去分词： 　　
如：We hope it will have stopped raining before we set off for the picnic. 我们希望在出发去野餐以前雨就已经停了。
         I'll have done all the work by the time you are back this evening. 你们今晚回来的时候我就将做完所有的工作了。 　　
（二）用法： 　　
1、表示在将来某一时刻将完成或在另一个未来的动作发生之前已经完成的动作。 　　
注意：常与将来完成时连用的时间状语有：
①by(the time/the end of)+表示将来时间的短语和句子； 　　
②before(the end of)+表示将来时间的词语或句子； 　　
③when, after等加上表示将来动作的句子等。
例如：By the year 2050, scientists probably will have discovered a cure for cancer.
            到2050年，科学家们可能已经找到治愈癌症的方法了。 　　
            By the time you arrive in London, we will have been staying in Europe for two weeks. 　　
            等你到达伦敦的时候，我们将已经在欧洲呆了两星期了。 　　
2、在时间从句和条件从句中，现在完成时可以代替将来完成时，表示将来某时业已完成的动作。
例如：You'll get to like the subject after you have studied it for some time. 　　
            在学习这个学科一段时间之后，你就会喜欢它的。 　　    
            I'll go and see the exhibition as soon as I have finished my work. 我一做完作业就去看展览。 　　
3、将来完成时还可以表示"可能性"，或"设想"。
例如：It's five o'clock, they will have arrived home by now. 已经五点钟了，他们现在应该已经到家了。

将来完成时与一般将来时的比较： 　　

1、有具体的时间状语要用一般将来时。
如：Mr Smith will return home on the first Sunday next month. 史密斯先生将于下月的第一个星期日回家。 　　
2、将来完成时的时间状语一般用介词by引入。
如：Mr Smith will have returned home by next month. 到下个月史密斯先生将已回到家了。 　　

典例精析： 　　
1、They_____on the program for almost one week before I joined them, and now we_____it as no good results have come out so far.　　
      A. had been working; are still working
      B. had worked; were still working 　　
      C. have been working; have worked
      D. have worked; are still working 　　
答案：A。 　　
解析：不难看出第一空的动作发生在I joined them以前，且持续了一个周，应该用过去完成进行时；and now说明下面的动作仍在进行之中，应该用现在进行时。故选A。 　　
2、Father_____for London on business up on my arrival, so I didn't see him.　　
      A.has left
      B.left
      C.was leaving
      D.had left 　　
答案：D。 　　
解析：由"I didn't see him"可知父亲在我回来以前已经离开，动作发生在过去某个动作以前，故选用过去完成时。 　　
3、The policeman's attention was suddenly caught by a small box which_____placed under the Minister's car.　
      A. has been
      B. had been
      C. was being
      D. would be　
答案：B。