QGraphicsView mouse move event not work to me

M_Hu

I have a qgraphicsview to plot signal. I would zoom specific area with mouse clicking and rectangle drawing. So I need mouse pressed position and dragged position. For this I do such this:

in header file:

	class QtGuiApplication : public QMainWindow
{
	Q_OBJECT

public:
	QtGuiApplication(QWidget *parent = Q_NULLPTR);

protected:
	void mouseMoveEvent(QMouseEvent* event);
	void mousePressEvent(QMouseEvent* event);
	bool eventFilter(QObject *obj, QEvent *ev);

private:
	QPoint Zoom_point1_;
	QPoint Zoom_point2_;
	QGraphicsScene* scene = new QGraphicsScene();

};

in source file:

	QtGuiApplication::QtGuiApplication(QWidget *parent)
	: QMainWindow(parent)
{
	ui.setupUi(this);
	ui.graphicsView->installEventFilter(this);
	ui.graphicsView->setMouseTracking(true);
}

bool QtGuiApplication::eventFilter(QObject * obj, QEvent * ev)
{
	if (obj == ui.graphicsView)
		if (ev->type() == QEvent::MouseMove)
		{
			QMouseEvent *mEvent = (QMouseEvent*)ev;
			Zoom_point2_ = mEvent->pos();
		}
	return false;
}
void QtGuiApplication::mouseMoveEvent(QMouseEvent * ev)
{
	Zoom_point2_ = ev->globalPos();
	//do some thing …
}

void QtGuiApplication::mousePressEvent(QMouseEvent * ev)
{
	Zoom_point1_ = ev->globalPos();	
}

When I press and move mouse in graphicsview, I can recognize the clicked position but mouseMoveEvent(QMouseEvent * ev) never be called! and also obj == ui.graphicsView statement in eventFilter never be occurred.What's wrong with me? How can I fix it?

SGaist

Hi,

Why are you re-implementing QMainWindow mouse related events as well as filter QGraphicsView ?

M_Hu

I want to recognize mouse event on graph area. so I think the filter must be installed on the qgraphview object. Is it wrong?

Andeol

Hi,

I think you have your event filter installation backward:

ui.graphicsView->installEventFilter(this);

Should be:

this->installEventFilter(ui->graphicsView);

So here, you are saying your mainWindow should spy on the event destined to your ui.graphicsView, while it's actually the opposite that you want.