Question

while后主句什么时候用进行时态什么时候用过去时态

Answer 1

while 后的是从句，是时间状语从句，可用进行时或过去时。如
while we were having dinner yesterday, there was a knock at the door.
I made many friends while I lived there. 这个词后的从句要用延续性动词。

Answer 2

while 从句中需用延续性动词的进行时，或表示状态意义的词，主句也要用延续性动词或表示状态的谓语，如
While he was in London , he made a lot of friends
While he was reading a newspaper, his son was watching TV.

Answer 3

1、while 的典型用法：
①Jack likes sports while Mike likes music.【表示对比转折，“而；然而”】
②While you are at the post office,please remeber to post the letter for me.
While we were waching TV, mother was cooking in the kitchen.
He picked up German while he was in Germany.
【时间状语从句，“在...期 间”，可位于句首或句中】
③ While he is a child ,he knows much about history.
【让步状语从句，“虽然；尽管”，只位于句首】
2、所用时态：
根据句子意思表达需要，选用合适的时态搭配——
当需要表达【两个动作同时进行】，可都用进行时态；
当需要表达【在一个动作进行时，另一动作突然发生或开始，可以用一般过去时或现在时】。可以参看上面的例句。
祝你开心如意！O(∩_∩)O~~