Check the error with QT

I m getting run time error in the following program..
Plz solve this one.
Actually the runtime error comes in
view.cpp file

myview->setwindow(mywindow)

myview.h:
class QTOPENCASCADE_EXPORT View
: public QGLWidget
{
Q_OBJECT

public:

View(QWidget *parent=0);
~View();

void Initialize(Handle_AIS_InteractiveContext);//,QWidget *);

Handle_AIS_InteractiveContext getContext( void ) { return myContext; }
Handle_V3d_View getView( void ) { return myView; }

protected:

protected:

void paintEvent ( QPaintEvent * e);

private:

Handle_V3d_View myView;
Handle_AIS_InteractiveContext myContext;

public:
short hi, lo;

};

#endif // View_H

view.cpp......
#include
#include
#include "View.h"
#include "viewer.h"
#include "mainwindow.h"
#include
#include
#include
#include

View::View(QWidget *parent) : QGLWidget(parent,0,0)//Qt::SubWindow)
{
//setParent(parent);
myView = NULL;
this->setAutoFillBackground( false );
//setMaximumSize(400, 400);
//showMaximized();

//setGeometry(0,0,1024,768);

int windowHandle = 0;
windowHandle=(int) winId(); // Error comes here
lo=hi=0;

lo = (short) windowHandle;
hi = (short) ( windowHandle >> 16 );

}

View::~View()
{

}

void View::Initialize(Handle_AIS_InteractiveContext aContext)
{
myContext=0;
myContext = aContext;

myView=0;
myView = aContext->CurrentViewer()->CreateView();

Handle(WNT_Window) myWindow = new WNT_Window(Handle(Graphic3d_WNTGraphicDevice)::DownCast(myContext->CurrentViewer()->Device()),(int) hi,(int) lo,Quantity_NOC_BLACK);

try
{
myView->SetWindow(myWindow);// here the run time error comes

}catch(Standard_MultiplyDefined)
{ (new QMessageBox(0))->show();

}
myView->SetBackgroundColor(Quantity_NOC_BLACK);

myWindow->SetFlags(WDF_NOERASEBKGRND);
if (!myWindow->IsMapped())
myWindow->Map();

myView->DoMapping();

myView->TriedronDisplay(Aspect_TOTP_LEFT_LOWER, Quantity_NOC_RED, 0.08);

myView->MustBeResized();
myView->SetDegenerateModeOff();
aContext->CurrentViewer()->SetViewOn(myView);

}

void View::paintEvent ( QPaintEvent * e)
{

if (!myView.IsNull())
myView->Redraw();
//getView()->Update();

}