QQmlVTKPlugin window initialization from QML

Hello,
I am using the QQMLvtkPlugin in my Qt Quick app. To do that the vtk documentation give the following example :

  QQuickVTKRenderWindow::setupGraphicsBackend();
  QGuiApplication app(argc, argv);
 
  QQmlApplicaQtionEngine engine;
  engine.load(QUrl("qrc:///<qmlfile>.qml"));
 
  QObject* topLevel = engine.rootObjects().value(0);
  QQuickWindow* window = qobject_cast<QQuickWindow*>(topLevel);
 
  window->show();
 
  // Fetch the QQuick window using the standard object name set up in the constructor
  QQuickVTKRenderItem* qquickvtkItem = topLevel->findChild<QQuickVTKRenderItem*>("ConeView");

However, in my app I want to initialize my qquickvtkItem from my main.qml. In order to do that I have a singleton testQML wich allows me to create my scene:

ApplicationWindow  {
    id: appWindow;
    readonly property SceneManage scene: TestQML.create(appWindow)
   ...

TestQML.create():

SceneManage *testQML::create(QQuickWindow *parent)
{
    SceneManage *scene = new SceneManage(parent);
    return scene;
}

But my app crashes when I do a window->show in the SceneManage constructor :

SceneManage::SceneManage(QObject *topLevel)
{
    window = qobject_cast<QQuickWindow *>(topLevel);   // QQuickWindow window
    window->show();
    QQuickItem *item = topLevel->findChild<QQuickItem *>("3DViewer");
...

Does someone have a way to solve this problem ? (The solution of the documentation and mine give the same adresses for window and the QQuickVTKRenderItem, so these are the right object)
Many thanks

Solution : Don’t decide to show the window from c++ but only set visible parameter in QML.