perfect cont. tense

[aysaa]

Hello

I would like to ask whether we can use 'present perfect con., future perfect cont....etc' without any adverb time such as for, all,...etc.

For example,

A: Have you finished your homework ?
B:Don't you see it! I have been trying to do my homework.

or

When you leave the house tomorrow, I will have been working at work.

What I mean is : Can we use them like that?

Note: I know that there are no meaning at the sentences, but I just wanted to ask as gramatical.

Thanks....

[5jj]

Note: I know that there are no meaning at the sentences, but I just wanted to ask as gramatical.

Try to create sentences that make sense. I have been weeding my diary is grammatically sound, but pointless. Sentences can only have real meaning if they are about a potentially real situation.

What have you been doing?
I have been trying to do my homework.

That's fine, but note that we do have an implied time reference - the present moment, and the period leading up to it.

I cannot imagine using a so-called 'future perfect continuous' without some form of time reference. 'I will have been working' on its own means nothing, unless we know the future time up to which the working will have been in progress.

[aysaa]

What will you have been doing when I go to bed tomorrow?
I will have been watching tv.

Is that impossible without some form of time reference?

[5jj]

Without the time reference, we have: What will you have been doing ?

With no other context or co-text, the only reasonable answer to that is, "When?