twice execution of click on pushbutton?

[rambo83]

You are right, now it works! But why? If I don't connect the SLOTs and SIGNALs automatically or manually, the click on button should not call the corresponding function at all, but it does now. Why?

[yogeshgokul]

You are right, now it works! But why? If I don't connect the SLOTs and SIGNALs automatically or manually, the click on button should not call the corresponding function at all, but it does now. Why?

Because you named them(slots) like that.
If you have a QPushButton named btn. And you created a slot named on_btn_clicked().
It will automatically get connected.
QT ROCKS

[spirit]

because of this "notice: QMetaObject::connectSlotsByName(this); is also used in generated ui_classname.h file."
read this QMetaObject::connectSlotsByName.

[squidge]

You are right, now it works! But why? If I don't connect the SLOTs and SIGNALs automatically or manually, the click on button should not call the corresponding function at all, but it does now. Why?

setupUi() calls connectSlotsByName. You are then calling it yourself too, thus you get two function call per click

[rambo83]

Thank you very much for the explanations. They were very helpful.