be doing when用法

“be doing sth.when...”用于表示當某人或某物正在或正要做某事，就在這時突然又發生了另一件事。另外與be doing sth.when有相同意思的句式還有be about to when.../be on the point of doing sth.when...等。

be doing when

表示“正在做某事，就在這時……”

(1)I was watching the football match when he came in.

當他走進來的時候我正在看足球賽。

(2)He asked me what I would be doing when he came the next day.

他問我當他第二天來的時候我會在干什么。

be about to when

表示“正要……這時(突然)……”。When在此為并列連詞，意為“就在這時(突然)”

(1)I was about to say when you interrupted me.

我正要說話的時候，你插嘴了。

(2)I was about to go out when the telephone rang.

我正要出去，電話鈴響了。

be on the point of doing sth.when

表示“正在做……，就在這時……”

She was on the point of watching TV when there was a power failure.

他剛要看電視，這時突然停電了。

had just done sth.when

表示“剛剛做完某事，就在這時……”

I had just gone to bed when the telephone rang.

我剛剛上床睡覺，電話鈴突然響了。