How to determine when QML window closed.

mulhaupt

I'm trying to determine when a QML window is closed from my c++ code.

There is the closing(QQuickCloseEvent*) signal - which is a little broken, because I can't use the new signal/slots on it since QQuickCloseEvent is private - ANYWAYS.. This signal isn't reliable since I could theoretically cancel the close (and if there are multiple listeners, I have no idea which order my listener would be called). I tried to subclass QQuickWIndow, but there doesn't even seem to be any virtual methods - like onClose(). I've seen people mention setting DeleteOnClose flag and wait for destroyed() signal, but this only seems to apply to widgets apps.

? Offline

Hi mulhaupt,

a simple solution could be to use the visibilityChanged signal. This example works for me:

// main.cpp 
#include <QApplication>
#include <QQmlApplicationEngine>
#include <QObject>
#include "dings.h"
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    Dings dings;
    QObject* rootObj = engine.rootObjects().at(0);
    QObject::connect(rootObj, SIGNAL(dingdong()), &dings, SLOT(sayHello()));
    return app.exec();
}

// dings.h
#ifndef DINGS_H
#define DINGS_H
#include <QObject>
#include <QDebug>
class Dings : public QObject
{
    Q_OBJECT
public:
    explicit Dings(QObject *parent = 0);
    ~Dings();
public slots:
    void sayHello() const { qDebug() << "hello"; }
};
#endif // DINGS_H

// dings.cpp
#include "dings.h"

Dings::Dings(QObject *parent) : QObject(parent)
{
}

Dings::~Dings()
{
}

// main.qml
import QtQuick 2.4
import QtQuick.Window 2.2

Window {
    title: qsTr("Hello World")
    width: 640
    height: 480
    visible: true

    signal dingdong

    onVisibilityChanged: {
        if (visibility==Window.Hidden)
            dingdong()
    }
}

Cheers!
Wieland

P.S.: I haven't figured out how to format code properly in the new forum yet. Sorry for that ;-)

p3c0

@Wieland put the code inside ``` (3 backticks)

p3c0

@mulhaupt If you subclass QQuickWindow you can use eventFilter to track the events. You will need to installEventFilter for it first. Eg.

//myqquickwindow.cpp
bool MyWindow::eventFilter(QObject *o, QEvent *e)
{
    if (e->type() == QEvent::Close)
    {
        qDebug() << "Closing";
        e->accept();
    }
    return QObject::eventFilter(o, e);
}

// And in constructor
installEventFilter(this);