Qt button assign command

Question

I'm using qt creator to create a gui for an vtk aplication.

I've made a #define action and I want to assign that command to a QPushButton.

How do I make the button reproduce my define if pressed?

example. ui->pushButton->...

Answer 1

The easy way is to define a default reponse slot for your button. In your class definition (the same class that defines the pushButton) you can just create a default slot under the slots section.

class MyMainApplication : public QMainWindow
{
  Q_OBJECT

  public:
    MyMainApplication(QWidget *parent = 0);
    ~MyMainApplication();

   // More stuff in the public section (...)

  public slots:
    void on_pushButton_clicked();    // This is the important line

  // The remaining definitions in your class
};

Now you just program the on_pushButton_clicked() function in your class implementation and it will respond to the click on the button called pushButton.

The syntax for default slots is on_NAMEOFTHEWIDGET_NAMEOFTHESIGNAL.

With the default slots, the connection is made automatically. If you want to use a generic name for the slot you must make the connection manually. For instance, say that instead of on_pushButton_clicked() you want to use mySlot(). In the class definition you would type

(...)
public slots:
  void mySlot();
(...)

and in the class implementation, probably in the constructor, after the ui->setupUi(this); command you would make the connection of the button and your slot:

connect(ui->pushButton, SIGNAL(clicked()), this, SLOT(mySlot()));

A final remark: in this particular case, I am almost sure that the slots can also be private.

Answer 2

You need to use Qt's feature called Signals and Slots. Many objects can send signals when interacted with. Example is "clicked()" signal emitted from a QPushButton, or "triggered()" which is emitted upon clicking on QAction.

Main idea is to connect a signal to a slot. Slots are functions which are called when a signal is emitted. I can provide you with a PyQt example:

QtCore.QObject.connect(self.ui.myButton, QtCore.SIGNAL("clicked()"), self.someFunction)

C++ code shouldn't be much different. Check the Qt examples, they provide lots of good stuff.