How to close a Qt qml application programmatically without errors? - c++

Question

I want to programmatically close a qml qt application.
I tried the method described here How to quit the C++ application in Qt QML
Qt.callLater(Qt.quit)
via qml and using
QObject::connect(&engine, &QQmlApplicationEngine::quit, &QGuiApplication::quit);
I also tried to close the application from c++ using QCoreApplication::quit(). And the method described in the qt documentation via signals and slots by calling the slot QGuiApplication::quit.
The problem is that the application closes with an error:
“The program has unexpectedly finished.”
“The process was ended forcefully.”
If I close the application with a standard cross, then the problem does not arise.
I suspect that the problem is in QQmlApplicationEngine. Because if I remove the line engine.load(url); then the application closes correctly.
I use QT 5.13.0 minGW and QT 5.13.0 MSVC2017 (32 and 64).
If I run in the debug, the application gives an error, but the error is absolutely not informative.
here is my application code c++:
#include <QGuiApplication>
#include <QTimer>
#include <QQmlApplicationEngine>
int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
QQmlApplicationEngine engine;
const QUrl url(QStringLiteral("qrc:/main.qml"));
engine.load(url);
QTimer* timer=new QTimer();
QObject::connect(timer, &QTimer::timeout, &app, &QGuiApplication::quit, Qt::QueuedConnection);
timer->start(2000);
return app.exec();
}
and code qml file:
import QtQuick 2.12
import QtQuick.Window 2.12
Window {
width: 640
height: 480
visible: true
title: qsTr("Hello World")
}
UPDATE:
I tried to compile Qt5.9.9 Qt5.13.0 QT5.15 and this problem occurs everywhere. But when I compiled with the Qt6.4 version, the problem disappeared and the application terminated correctly. Anyway, I'll leave the question open.

Answer 1

As JarMan pointed out QTimer::singleShot() can be used to close your application. In fact, this is the example provided straight from the documentation https://doc.qt.io/qt-6/qtimer.html#singleShot :
#include <QApplication>
#include <QTimer>
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QTimer::singleShot(600000, &app, SLOT(quit()));
...
return app.exec();
}