You do not show us the implementation of the interface.
Further, you dont HAVE to store a variable like “isMainMenuShow” outside of the widget as you can read these values from the widget itself.
Show us the implementation of the interface and show us what classes each of the pictures are from. You are calling the TestFunc on self, but self is NOT a widget it seems. I also dont understand why you would use an interface to call a function within the same calss.