在qtmain.cpp中为与qml通信而强制转换rootobject()时出错

Question

我是qt quick的新手，我试着写一段代码来调用qml信号上的c++插槽

//main.cpp 
#include "qtquick1applicationviewer.h"
#include "QApplication"
#include"authenticate.h"
     int main(int argc, char *argv[])
     {
      QApplication app(argc, argv);
      QDeclarativeView view(QUrl::fromLocalFile("MyItem.qml"));
      QObject *item = view.rootObject();
      Authenticate myClass;
      QObject::connect(item, SIGNAL(qmlSignal(QString)),
                     &myClass, SLOT(cppSlot(QString)));
     view.show();
    return app.exec();
}

错误为：main.cpp:15:错误：初始化时无法将"QGraphicsObject*"转换为"QObject*"QObject*item=viewer.rootObject（）；

     //main.qml
     import QtQuick 1.0 
    Item {
    id: item
    width: 100; height: 100
    signal qmlSignal(String msg)
    MouseArea {
        anchors.fill: parent
        onClicked: item.qmlSignal("Hello from QML")
    }
}

                                       ^

Answer 1

您应该显式转换为QObject *:

QObject *item = qobject_cast< QObject * >( view.rootObject() );

还要确保您已包含QGraphicsObject:

#include <QGraphicsObject>