have a good time和have fun后为什么要跟doing sth

问题描述:

have a good time和have fun后为什么要跟doing sth

不一定要跟的.但当你要说做一件事的心情时就可以这样说
做……很愉快;(或很愉快地做……)
做……很有趣;(或很有趣地做……)
就加上(in) doing sth
I am having a good time.我很愉快.
I am having a good time (in) playing pingpong.我打乒乓球很愉快.
还有
I have some trouble (in) learning math.