Question

I have a simple setup to change a label on a timed interval, for testing purposes. It seems that the signal does not ever get emitted. I’m using Visual Studio 2010 with the Qt add-in. Here is my setup…

Window::Window(QWidget *parent, Qt::WFlags flags)
    : QMainWindow(parent, flags)
{
    ui.setupUi(this);
    my_label = new QLabel();

    timer = new QTimer(this);
    timer->setInterval(1000);
    connect(timer, SIGNAL(timeout()), this, SLOT(nextFrame()));
}

void Window::nextFrame()
{
    static int i = 0;
    std::stringstream ss;

    ss << "C:/files/" << i << ".txt";
    QString qstr = QString::fromStdString(ss.str());
    ui.label->setText(qstr);

    ss.str("");
    i++;
    repaint();
}

And in the header file,

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

public slots:
    void nextFrame();

private:
    Ui::TrackerClass ui;
    QTimer *timer;
};

Why is the slot nextFrame() never being triggered?

Answer 1

There is nothing in this code which calls start() and so based on this code nextFrame() would never be triggered by timeout().