如何在Qt和QML之间建立信号槽链接

下面的例子讲述了在Qt和QML代码之间建立信号槽链接。这里需要注意：由于QML中的函数是JavaScript，这些函数的参数是没有类型的。
在建立信号槽时需要使用QVariant类型。

myclass.h

#ifndef MYCLASS_H
#define MYCLASS_H
 
#include <QObject>
#include <QVariant>
 
class MyClass : public QObject
{
    Q_OBJECT
 
public:
    MyClass() {}
 
public slots:
    void getData() {
        QString text("New data");
        emit data(QVariant(text));
    }
 
signals:
    void data(QVariant data);
};
 
#endif // MYCLASS_H

main.cpp

#include <QApplication>
#include <QGraphicsObject>
#include <QDeclarativeView>
#include <myclass.h>
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
 
    MyClass myClass;
 
    QDeclarativeView view;
    view.setSource(QUrl("./ui.qml"));
    view.setResizeMode(QDeclarativeView::SizeRootObjectToView);
 
    QObject *rootObject = dynamic_cast<QObject*>(view.rootObject());
 
    QObject::connect(rootObject, SIGNAL(dataRequired()), &myClass, SLOT(getData()));
    QObject::connect(&myClass, SIGNAL(data(QVariant)), rootObject, SLOT(updateData(QVariant)));
 
#if defined(Q_WS_MAEMO_5)
    view.setGeometry(QRect(0,0,800,480));
    view.showFullScreen();
#elif defined(Q_WS_S60)
    view.setGeometry(QRect(0,0,640,360));
    view.showFullScreen();
#else
    view.setGeometry(QRect(100,100,800, 480));
    view.show();
#endif
 
    return app.exec();
}

ui.qml

// ui.qml
import Qt 4.7
 
Rectangle {
    signal dataRequired;
 
    function updateData(text) { dataText.text = text }  // slot
 
    anchors.fill: parent; color: "black"
 
    Text {
        id: dataText
        anchors.centerIn: parent; color: "white"
    }
 
    MouseArea {
        anchors.fill: parent
        onClicked: dataRequired()
    }
}

在这个例子中，我们在Qt和QML之间建立了双向链接，当rootObject的信号 dataRequired触发时，
myClass的 getData被调用；当myClass的信号data触发时, rootObject的updateData被调用

来源：http://www.thisisqt.com/?action-viewnews-itemid-10