VTK resliceCursorWidget compatibility with QT

I am working on the medical GUI development with QT and VTK. I have made MPR (MultiPlanar reformation) in VTK alone, but it does not display when I show it in QT (basically I add the renderwindow and renderer to QVTKWidget). I also tried QVTKOpenGLNativeWidget as an option, but it does not work as well. I knew it needs vtkGenericOpenGLRenderWindow where for display.

coding environment:

QT5.9 VS2017 VTK8.2.0

alone:

in QT:

here is my code

void BorderWidgetQt::openMPRwindow(QVTKWidget* qvtkwidget) {
    QVTKInteractor* iren = qvtkwidget->GetInteractor();
    vtkRenderWindow* renWin = qvtkwidget->GetRenderWindow();

    vtkSmartPointer<vtkDICOMImageReader> reader = vtkSmartPointer<vtkDICOMImageReader>::New();
    reader->SetDirectoryName("C:\\Users\\u\\source\\repos\\myrobotapp\\DICOM");
    reader->Update();

    vtkSmartPointer<vtkRenderer> ren; //vtksmartpointer 
    //vtkSmartPointer<vtkRenderWindow> renWin = vtkSmartPointer<vtkRenderWindow>::New();
    renWin->SetMultiSamples(0);

    ren = vtkSmartPointer<vtkRenderer>::New();
    renWin->AddRenderer(ren);

    //vtkSmartPointer<vtkRenderWindowInteractor> iren = vtkSmartPointer<vtkRenderWindowInteractor>::New();
    iren->SetRenderWindow(renWin);


    //renWin->SetInteractor(iren);
    vtkSmartPointer<vtkProperty> ipwProp = vtkSmartPointer<vtkProperty>::New();

    int imageDims[3];
    reader->GetOutput()->GetDimensions(imageDims);
    for (int i = 0; i < 3; i++) {
        std::cout << "imagesize L X W X H: " << imageDims[i] << std::endl;
    }

    vtkSmartPointer< vtkResliceCursor > resliceCursor = vtkSmartPointer< vtkResliceCursor >::New();
    resliceCursor->SetCenter(reader->GetOutput()->GetCenter());
    resliceCursor->SetThickMode(1);// mode 1 or more and thickness can be viewed 
    //set image that are resliced
    resliceCursor->SetImage(reader->GetOutput());

    vtkSmartPointer< vtkResliceCursorWidget > resliceCursorWidget;
    vtkSmartPointer< vtkResliceCursorLineRepresentation > resliceCursorRep;
    //camera viewup
    double viewUp[3][3] = { { 1, 0, -1 }, { 0, 0, 1 }, { 0, 1, 0 } };
    /************************/
    resliceCursorWidget = vtkSmartPointer< vtkResliceCursorWidget >::New();
    resliceCursorWidget->SetInteractor(iren);

    resliceCursorRep = vtkSmartPointer< vtkResliceCursorLineRepresentation >::New();
    resliceCursorWidget->SetRepresentation(resliceCursorRep);
    resliceCursorRep->GetResliceCursorActor()->GetCursorAlgorithm()->SetResliceCursor(resliceCursor);
    //thickness text is ediable and can turn off
    //resliceCursorRep->DisplayTextOff();
    resliceCursorRep->GetResliceCursorActor()->GetCursorAlgorithm()->SetReslicePlaneNormal(0);
    cout << "number of input port: " << resliceCursorRep->GetResliceCursorActor()->GetCursorAlgorithm() << endl;
    const double minVal = reader->GetOutput()->GetScalarRange()[0];
    std::cout << "minVal: " << minVal << " maxVal: " << reader->GetOutput()->GetScalarRange()[1] << endl; //0~1059

    if (vtkImageReslice *reslice = vtkImageReslice::SafeDownCast(resliceCursorRep->GetReslice()))
    {
        reslice->SetBackgroundColor(minVal, minVal, minVal, minVal);
    }

    resliceCursorWidget->SetDefaultRenderer(ren);
    resliceCursorWidget->SetEnabled(1);
    ren->GetActiveCamera()->SetFocalPoint(0, 0, 0);
    double camPos[3] = { 1, 0, 0 };
    ren->GetActiveCamera()->SetPosition(camPos);
    ren->GetActiveCamera()->ParallelProjectionOn();
    ren->GetActiveCamera()->SetViewUp(viewUp[0][0], viewUp[0][1], viewUp[0][2]);
    ren->ResetCamera();


    double range[2];
    reader->GetOutput()->GetScalarRange(range);
    std::cout << "range[0]: " << range[0] << " range[1]: " << range[1] << endl; // 0~1059
    //cover full range of window
    resliceCursorRep->SetWindowLevel(range[1] - range[0], (range[0] + range[1]) / 2.0);
    //resliceCursorRep->SetLookupTable(resliceCursorRep->GetLookupTable());
    //reslice cursor center
    vtkResliceCursor *rc = resliceCursorRep->GetResliceCursorActor()->GetCursorAlgorithm()->GetResliceCursor();
    double *center = rc->GetCenter();
    std::cout << "cursor center: " << " [x]: "
        << center[0] << " [y]: " << center[1] << " [z]: " << center[2] << endl;
    /************************/


    //background of window
    ren->SetBackground(0.3, 0.1, 0.1);

    //whether it is a hole in the center of two cross hair
    resliceCursor->SetHole(0);
    resliceCursor->SetThickness(2, 2, 2);
    cout << "thickness is : " << resliceCursor->GetThickness()[0] << endl;

    vtkSmartPointer< vtkInteractorStyleImage > style = vtkSmartPointer< vtkInteractorStyleImage >::New();
    iren->SetInteractorStyle(style);
    renWin->Render();
    //iren->Initialize();
    //iren->Start();

}

it was solved when I just claim the following in head file and make corresponding change in cpp:

private:
vtkSmartPointer< vtkResliceCursorWidget > resliceCursorWidget;

I don't know the depth of the solution. Maybe the QT cannot read the source file if it is not claimed, and also it needs timely render the source.