QWidget: Must construct a QApplication before a QWidget

Support
#1

Hi,

Getting the following error while try to run application.
QWidget: Must construct a QApplication before a QWidget

Below is a snippet of code.

#include <QApplication>

#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>

#include <QVTKWidget.h>

int main(int argc, char** argv)
{
	QApplication app(argc, argv);

	QVTKWidget widget;
	widget.resize(256, 256);

	vtkSmartPointer<vtkSphereSource> sphereSource =
		vtkSmartPointer<vtkSphereSource>::New();

	vtkSmartPointer<vtkPolyDataMapper> sphereMapper =
		vtkSmartPointer<vtkPolyDataMapper>::New();
	sphereMapper->SetInputConnection(sphereSource->GetOutputPort());

	vtkSmartPointer<vtkActor> sphereActor =
		vtkSmartPointer<vtkActor>::New();
	sphereActor->SetMapper(sphereMapper);

	vtkSmartPointer<vtkRenderer> renderer =
		vtkSmartPointer<vtkRenderer>::New();
	renderer->AddActor(sphereActor);

	widget.GetRenderWindow()->AddRenderer(renderer);
	widget.show();

	app.exec();

	return EXIT_SUCCESS;
}

VTK- 8.2.0
Qt- 5.12.2
VS- 2017

Can somebody please help me ?

#2

Hi,

I’m stuck exactly with the same problem.

Did you find a solution? It’s been a while since you posted, but it would be much appreciated if your share the solution you found, if any.

Thanks in advance.
Best regards,
Alex

#3

First hit on Google explains it: