Problem with auto-complete in Qt creator

Hi,
I am a new user of Qt creator.
Since I was looking for a free and permanent version of it, I found that the only way was installing the one on "Ubuntu Software Center".
For this reason, I am using version 3.5 of Qt creator.

I can compile and run my program regularly, but the auto-complete is not working.

How it is shown in the image, it does not find any kind of library ( like "ui_mainwindow.h" and "QMessageBox" ) showing the error: "No such file or directory".
But then if I run, as I said, everything is working regularly.

What should I do in order to make the auto-complete working ?


Attachment 11787