Signal from C++ in QML

Trikrista

There is a code like this

@
// interfaceqml.h

class InterfaceQML : public QObject {
Q_OBJECT

public:
InterfaceQML(QObject *parent = 0);
int t;

signals:
void newSignal(int i);

public slots:
void newSlot();
};
@

@
//interfaceqml.cpp

InterfaceQML::InterfaceQML(QObject *parent) : QObject(parent) {
t = 0;
}

void InterfaceQML::newSlot() {

emit newSignal(t);
t++;

}
@

@
//mainwindow.h

class MainWindow : public QObject {
Q_OBJECT
public:
MainWindow(QObject *parent = 0);
InterfaceQML *interface;
QQuickView *view;
QTimer *timer;
};
@

@
//mainwindow.cpp

MainWindow::MainWindow(QObject *parent) : QObject(parent) {
interface = new InterfaceQML;
timer = new QTimer;
view = new QQuickView;

qmlRegisterType<InterfaceQML>("Interface", 1, 0, "Interface");

view->setSource(QUrl("file:/main.qml"));
view->show();
QObject *pObject = view->rootObject();

connect(timer, SIGNAL(timeout()), interface, SLOT(newSlot()));
timer->start(500);

}
@

@
//main.gml

import QtQuick 2.0
import Interface 1.0

Rectangle {
width: 500
height: 500
color: "#748596"

signal sgSignal()

Text {
    id: text
    anchors.horizontalCenter: parent.horizontalCenter
    anchors.verticalCenter: parent.verticalCenter

    text: "World"
    font.bold: true
    font.pointSize: 30
    color: "red"
}

Interface {
    onNewSignal: {
        text.text = i
    }
}

}
@

But signal not reach QML. How fix it?

sierdzio

You are instantiation 2 separate Interface objects: one in C++, and another in QML. No wonder it does not work. Get a pointer to your QML instance using QObject::findChildren() (just remember that findChildren requires your QML object to be named in "objectName" property for the method to work) or use a timer in QML and trigger it from there.

There are a few other ways to do it, but I won't flood you with information right now.

Trikrista

So I did.

@
//interfaceqml.cpp

InterfaceQML::InterfaceQML(QObject *parent) : QObject(parent) {
    t = 0;
    emit newSignal(t);
}
 ...

@

@
//mainwindow.cpp

MainWindow::MainWindow(QObject *parent) : QObject(parent) {
timer = new QTimer;
view = new QQuickView;

qmlRegisterType<InterfaceQML>("Interface", 1, 0, "Interface");

view->setSource(QUrl("file:/main.qml"));
view->show();
QObject *pObject = view->rootObject();
InterfaceQML *interface = pObject->findChild<InterfaceQML *>();

connect(timer, SIGNAL(timeout()), interface, SLOT(newSlot()));
timer->start(500);

}
@

Thanks