Opencv image in qt3d

[sunil.nair]

Hello, i am successfully able to integrate QT with opencv using this tutorial:

http://stackoverflow.com/questions/15881913/how-to-link-opencv-in-qtcreator-and-use-qt-library

However, i am trying to write the code not in the main.cpp file but in a different cubevie.cpp file that comes as a tutorial with qt3d.

@/*
****************************************************************************/
#include <QApplication>
#include "cubeview.h"
#include "qglbuilder.h"
#include "qglcube.h"
#include "haptics.h"
#include <iostream>
#include <QThread>
#include <QTimer>
#include <QDebug>
#include "qglpainter.h"
#include "qgraphicstranslation3d.h"
#include "opencv2/core/core.hpp"
#include "opencv2/highgui/highgui.hpp"
//#include "opencv/cv.h"

//! [1] constructor, initialize the cube, cursor and camera
CubeView::CubeView(QWidget *parent)
{
//opencv code
cv::Mat image;
image= cv::imread(":/blackcircle.jpg");
cv::namedWindow("hello");
cv::imshow("hello", image)

//! [1]
QGLBuilder builder1;
builder1 << QGL::Faceted;
builder1 << QGLCube(2);
cube = builder1.finalizedSceneNode();

//camera setup
camera()->setFieldOfView(35);
camera()->setNearPlane(1);
camera()->setFarPlane(15);

//! [2] set texture for cube and cursor
logo.setImage(QImage(QLatin1String(":/blackcircle.jpg")));

}

CubeView::~CubeView()
{
logo.cleanupResources();
delete cube;
}
//! [3]
void CubeView::paintGL(QGLPainter *painter)
{
painter->setStandardEffect(QGL::LitDecalTexture2D);
logo.bind();
cube->draw(painter);

}

@

*But this gives me the following error.
QWidget: Cannot create a QWidget without QApplication
Invalid parameter passed to C runtime function.

Is it because, already a window is open and I cannot open another window to see my image?*