Why is the Qt event loop left - qt

Question

I want a small program doing the following:
start a single-shot QTimer
when it times out, a QMessageBox is shown
if button "Continue" is clicked, the box is closed and the timer restarted
if button "Stop" is clicked, the box is closed and the application exited
The problem I have is that the event loop is left as soon as I hide the message box. The box is displayed only once. I reproduced my program in a console version and it runs as expected. Here is my code. Thanks in advance for your help.
main.c
#include <QtGui/QApplication>
#include "TimedDialog.h"
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
TimedDialog dialog(&app, SLOT(quit()));
dialog.run();
return app.exec();
}
TimedDialog.h
#ifndef TIMED_DIALOG_H
#define TIMED_DIALOG_H
#include <QObject>
#include <QTimer>
class QMessageBox;
class QPushButton;
class QAbstractButton;
class TimedDialog : public QObject
{
Q_OBJECT
public:
TimedDialog(
QObject const * receiver,
char const * method);
~TimedDialog();
void run(void);
signals:
void stop(void);
private:
QMessageBox* _box;
QPushButton* _buttonContinue;
QPushButton* _buttonStop;
QTimer _timer;
static int const DELAY = 2 * 1000; // [ms]
private slots:
void onTimeout(void);
void onButtonClicked(QAbstractButton * button);
};
#endif
TimedDialog.cpp
#include <assert.h>
#include <QMessageBox>
#include <QPushButton>
#include "TimedDialog.h"
TimedDialog::TimedDialog(
QObject const * receiver,
char const * method)
: QObject(),
_box(0),
_buttonContinue(0),
_buttonStop(0),
_timer()
{
_box = new QMessageBox();
_box->setWindowModality(Qt::NonModal);
_box->setText("Here is my message!");
_buttonContinue = new QPushButton("Continue");
_box->addButton(_buttonContinue, QMessageBox::AcceptRole);
_buttonStop = new QPushButton("Stop");
_box->addButton(_buttonStop, QMessageBox::RejectRole);
_timer.setSingleShot(true);
assert(connect(&_timer, SIGNAL(timeout()), this, SLOT(onTimeout())));
assert(connect(_box, SIGNAL(buttonClicked(QAbstractButton *)), this, SLOT(onButtonClicked(QAbstractButton *))));
assert(connect(this, SIGNAL(stop()), receiver, method));
}
TimedDialog::~TimedDialog()
{
delete _box;
}
void TimedDialog::onTimeout(void)
{
_box->show();
}
void TimedDialog::onButtonClicked(QAbstractButton * button)
{
_box->hide();
if (button == _buttonContinue)
{
_timer.start(DELAY);
}
else
{
emit stop();
}
}
void TimedDialog::run(void)
{
_timer.start(DELAY);
}

Answer 1

The created timer is being set as singleshot, which has already called timeout.
If you look at QTimer source code for the call to start() you can see it states: -
If singleShot is true, the timer will be activated only once.
You could fix and simplify the code with the class function QTimer::singleShot