THE PRESENT PERFECT CONTINUOUS
1. Focuses on the continuity of an action completed repeatedly or performed uninterruptedly up to the moment of speaking and whose performance is considered unfinished, unless it is ended as a result of a contingent action, so it is used to ask or say how long:
I’ve been decorating the house this summer. The focus is on the action (decorating) which is unfinished.
I’ve been reading that book you lent me. I’ve got another 50 pages to read.
I've been calling Linda all day but she isn't answering the phone
Here you are! I've been looking for you all day (the action stops because I've found him)
2. It's also used to speak about actions we see as temporary:
I usually work in London but I’ve been working in Birmingham for the last 3 weeks.
With static verbs it is necessary to use the simple form.
Thanks, I've been lost all this time (but now I've found you, so the action has stopped)
This is also true with the negative form
I have not heard from Liza all this week
Unless we need to contradict an assumption or express the opposite of a normal situation
I haven't been studying science, but maths
I haven't been feeling too well today
It may also be used with verbs which are treated as such, like work, smoke, collect and play, (to avoid being wrong better use them always in the continuous form)
I have lived in Milan since 1996 (uninterrupted action that may stop now or go on into the future. Period = 1996 - now, includes past and present)
If you use "since" and "for" the present perfect simple is the same as present perfect continuous
The presenter has been speaking for 45 min.
The presenter has spoken for 45 min.
If I say
The presenter has spoken (without "for"),
the action's finished (the action is important, the time is indefinite, it's not important)
It's better to use the present perfect continuous when we want to focus on how long
3.The present perfect continuous is also used to explain a present condition:
why are your eyes red? have you been crying?