什么情况下复合句(如While I was watching TV,he came in)中两个句子用过去进行时?

什么情况下复合句(如While I was watching TV,he came in)中两个句子用过去进行时?
什么情况下复合句(如While I was watching TV,he came in)中两个句子用过去进行时?

什么情况下复合句(如While I was watching TV,he came in)中两个句子用过去进行时?
表示对比.
While she was dancing,her brother was doing his homework.

楼上的也是，还有就是前后两个动词都必须是可持续性的，不能是瞬间性动词。