will do和will be doing有何区别?i will do something.i will be doing something.在什么情况下使用第一种,什么情况下使用第二种.有何区别?

第一个我将要干什么
第二个我将正在干什么
i will work hard。
i will be doing my homework at 9'clock.(我今完9点将会正在写作业)

Sorry, all above me are wrong.
The difference is within promise and determination.
When I say I will visit China in the fall to see you. It means I have the intention of so doing.
When I say I will be visiting China in the fall to see you. It means I have made the promise and I am determined to visit China.

我来更好诠释下tatyu的回答:i will do something是指我有这个意愿,打算但奏不奏效是以后的事,也是未必的.一般你没有太多一定的把握的话就用这个吧
i will be doing something说明自己已很肯定的相信到时自己会正进行这些事,所以说是很肯定,有决心,并带有种许诺的意味,听到得的人可以带有期待啊

will do 是一般将来时
will be doing 是将来进行时，用时一般都有表时间点的词
第一种意为我将要干某事。如：I will go to school.
第二种是在那时我将正在干某事。如：I will be working in my office this time tomorrow.