Question

I am using the QT integrated designer in Visual Studio 2010 to design a simple GUI. Here is what I want to do: I want to click a button called Update and use that to change an image that is displayed. I’ve verified that I am able to trigger a signal by pressing an update and used a slot on a text-field to clear. But can’t seem to change the image displayed using the Signal/Slot method ….

Here is the relevant code snippet (GUI.cpp):

 void GUI::changeImage() 
 {
     ui.Image->updatesEnabled();
     ui.Image->setPixmap(QPixmap("D:\\Documents\ and\ Settings\\Image.jpg"));
     ui.Image->update();
 }

GUI::GUI(QWidget *parent, Qt::WFlags flags)
    : QMainWindow(parent, flags)
{
    ui.setupUi(this);

    connect(ui.updateButton, SIGNAL(clicked()), ui.textField, SLOT (clear()) );
    connect(ui.updateButton, SIGNAL(clicked()), ui.Image, SLOT ( changeImage() ) );
}

GUI::~GUI()
{

}

Am I doing something wrong?

EDIT: The code for gui.h

#include <QtGui/QMainWindow>
#include "ui_gui.h"

class GUI : public QMainWindow
{
    Q_OBJECT

public:
    GUI(QWidget *parent = 0, Qt::WFlags flags = 0);
    ~GUI();

private:
    Ui::GUIClass ui;
    void changeImage() ;
};

Answer 1

The slot belongs to the GUI class instance, not to ui.Image, so you should use this as the target in the connect call.

connect(ui.updateButton, SIGNAL(clicked()), this, SLOT ( changeImage() ) );

The slots have to be declared under a “slots” section:

private slots:
    void changeImage() ;