Static timer attribute - undefined reference error

[Leutzig]

Hi,

I'm my application I have a class that sends the user back to the login page after 2 minutes of inactivity. On a specific page the application shouldn't go back to the login page, and therefore I've made a stopTimer() function, so this won't happen. To call this function without the need of using the InactivityFilter object created in main() I've made the timer static as well as stopTimer() and resetTimer(). This gives me a few of the following error:

/home/stud/FV/FlexVault/FlexVault_Qt/inactivityfilter.h:19: error: undefined reference to `InactivityFilter::timer'

Why is that?
How do I fix it?
Should I use signal and slots to call stopTimer() and resetTimer() from the page where I need to stop the timer?

My InactivityFilter is shown below:

#ifndef INACTIVITYFILTER
#define INACTIVITYFILTER
 
#include <QtCore/QCoreApplication>
#include <QTimer>
#include <QProcess>
 
namespace Ui {
class InactivityFilter;
}
 
class InactivityFilter : public QObject
{
    Q_OBJECT
 
public:
    explicit InactivityFilter()
    {
        timer = new QTimer(this);
        timer->setSingleShot(true);
 
        connect(timer, SIGNAL(timeout()), this, SLOT(showLogin()));
        resetTimer();
    }
 
    bool eventFilter(QObject *obj, QEvent *ev)
    {
      if(ev->type() == QEvent::KeyPress ||
         ev->type() == QEvent::MouseMove)
           resetTimer();
 
      return QObject::eventFilter(obj, ev);
    }
 
    static void resetTimer()
    {
        timer->start(120000);
    }
 
    static void stopTimer()
    {
        timer->stop();
    }
 
public slots:
    void showLogin()
    {
        qApp->quit();
        QProcess::startDetached(qApp->arguments()[0], qApp->arguments());
    }
 
private:
static QTimer *timer;
};
 
#endif // INACTIVITYFILTER

#ifndef INACTIVITYFILTER
#define INACTIVITYFILTER

#include <QtCore/QCoreApplication>
#include <QTimer>
#include <QProcess>

namespace Ui {
class InactivityFilter;
}

class InactivityFilter : public QObject
{
    Q_OBJECT

public:
    explicit InactivityFilter()
    {
        timer = new QTimer(this);
        timer->setSingleShot(true);

        connect(timer, SIGNAL(timeout()), this, SLOT(showLogin()));
        resetTimer();
    }

    bool eventFilter(QObject *obj, QEvent *ev)
    {
      if(ev->type() == QEvent::KeyPress ||
         ev->type() == QEvent::MouseMove)
           resetTimer();

      return QObject::eventFilter(obj, ev);
    }

    static void resetTimer()
    {
        timer->start(120000);
    }

    static void stopTimer()
    {
        timer->stop();
    }

public slots:
    void showLogin()
    {
        qApp->quit();
        QProcess::startDetached(qApp->arguments()[0], qApp->arguments());
    }

private:
static QTimer *timer;
};

#endif // INACTIVITYFILTER

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// Leutzig

[anda_skoa]

A static member of a C++ class needs to be defined in one of the compilation units additional to being declared in the class.

Cheers,
_