Hi high_flyer,
thanks a lot for your help. I did my project again from the beginning and everything is fine at the moment. It works and I could compile it without any problem.
As you said, I did it wrong the first time because I was mixing KWidgets and QWidgets. Now i did It taking care about that and everything worked without problems.
But now I have a problem with the actions of the menu.
In the GUI there is a menu, 4 bottoms, each one is doing one actions, but I want the actions, all the results of that actions, appear in the GUI, in one on the areas that I create for that. Now, all the results are appearing in the terminal, not in the GUI. These areas are QTextEdit, but I don't know if there is another element to put instead of textEdit to do it, to do that the results appear in this area. Or maybe I missed some instruction....
Thanks a lot again.