CODEWITHSUNDEEP
c++qt4qgraphicsview
bahree
bahree

Reputation: 586

Why does my QGraphicsView not showing up in my MainWindow in Qt4?

This is probably something very obvious, but I have a new to Qt and can't figure it out. I have a simple MainWindow which has one button. When that button is clicked I want to create a QGraphicsScene, add a few lines and then show that in the Window. However when I run this code in a Window it does not show up.

BUT, if I run this as a QApplication, it shows up just fine. What am I missing?

Here is the code in the MainWindow:

void TheDrawings::drawScene() {
 qDebug() << "Setting up Scene";

 QGraphicsScene scene(QRect(-50, -50, 400, 200));

 QPen pen(Qt::red, 3, Qt::DashDotDotLine);

 QGraphicsRectItem *rectItem = new QGraphicsRectItem(QRect(-50, -50, 400,
   200), 0, &scene);
 rectItem->setPen(pen);
 rectItem->setBrush(Qt::gray);

 QGraphicsSimpleTextItem *textItem = new QGraphicsSimpleTextItem(
   "Amit Bahree", 0, &scene);
 textItem->setPos(50, 0);

 QGraphicsEllipseItem *eclipseItem = new QGraphicsEllipseItem(QRect(170, 20,
   100, 75), 0, &scene);
 eclipseItem->setPen(QPen(Qt::darkBlue));
 eclipseItem->setBrush(Qt::darkBlue);

 QGraphicsPolygonItem *polygonItem = new QGraphicsPolygonItem(QPolygonF(
   QVector<QPointF> () << QPointF(10, 10) << QPointF(0, 90)
     << QPointF(40, 70) << QPointF(80, 110) << QPointF(70, 20)),
   0, &scene);
 polygonItem->setPen(QPen(Qt::darkGreen));
 polygonItem->setBrush(Qt::yellow);

 qDebug() << "Setting up the view";
 QGraphicsView view;
 view.setScene(&scene);
 view.show();

}

Upvotes: 1

Views: 6171

Answers (1)

serge_gubenko
serge_gubenko

Reputation: 20482

your QGraphicsView needs a centralwidget of the mainwindow (or whatever widget you want to put it on top of) to be set as a parent. Also you need to "new" your view and scene objects to put them on the heap so they don't get destroyed once drawScene finishes. See of following changes to your code would work fine for you:

QGraphicsScene* scene = new QGraphicsScene(QRect(-50, -50, 400, 200));
...
QGraphicsView* view = new QGraphicsView(ui->centralWidget);
view->setScene(scene);
view->setGeometry(QRect(50, 50, 400, 200));
view->show();

hope this helps, regards

Upvotes: 4

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