Peter came in while /as I was watching TV.当Peter进来的时候我正在看电视.

这两种翻译都可以,只不过是注意英语中短暂性的动词不能用于进行时态,所以不能说Peter was coming in while I was watching TV.
希望能帮到你,祝更上一层楼O(∩_∩)O
有不会的欢迎再继续问我(*^__^*)