c++ - 在 qt main.cpp 中转换 rootobject() 以与 qml 通信时出错

Question

我是 qt quick 的新手，我尝试编写代码来在 qml 信号上调用 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();
}

错误是: main.cpp:15: 错误:无法在初始化时将“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() );

还要确保你包含了QGraphicsObject:

#include <QGraphicsObject>