Providing some idea what you want help with would be useful. Are you having trouble compiling, running, making it work at all, warning messages...?

Obvious issues:
  • QPushButton does not emit a signal activated() and you should be receiving a warning to this effect when you run the program. Try clicked().
  • You call the QPushButton "button" in where you create it, and ui.action_button where you try to connect() it. Does the value of "button" get placed into ui.action_button anywhere?


Other observations:
  • Your "Interface header file" is an unusual place to put implementation details. Is this the header file the one that Designer/uic has built for you or one of your own creation?
  • You also seem to be trying to manually position the widget rather than using the Qt layout system. While allowable, this is probably a bad idea.


Edit: Zlatomir beat me to it.