Adding QgraphicsScene to my QgraphicsView

[procompmx5]

Hello everyone,

I have a problem. I'm trying to add a QgraphicsScene to my QgraphicsView (that I adding in QT designer) If I construct a QgraphicsView from code it works fine (It will create a new window though and I don't need that.)

My QgraphicsView that I make in Designer is called game_view i'm trying to add the view as such... game_view->setScene(&scene)

When I do this I don't have any errors but nothing is appearing in the view!

Any help is good help

Thank you
Chris

[meazza]

Well do you have any items in your scene that should show up? Otherwise the scene it self is just blank white. Also how do you create the scene?

[Lykurg]

"&scene" leads only to one conclusion (most likely): You created the scene on the stack, thus it is getting destroyed at the end of the function. Allocate the scene on the heap or as a member variable of the class which contains the view.

[procompmx5]

Yes the scene is populated...

I'm a bit confused by what you mean this is part of my code...

I borrowed some code from the QT examples for this,

#include <QtGui> 
#include <QPrinter>
#include <QGraphicsScene>
#include <QStyleOption>
#include <math.h>
#include "myqtapp.h"
 
#include "mouse.h"
 
static const int MouseCount = 2;
 
myQtApp::myQtApp(QWidget*)
{
	setupUi(this);
	connect( pushButton_newgame, SIGNAL( clicked() ), this, SLOT( newgame() ) );
     QGraphicsScene scene;
     scene.setSceneRect(-100, -100, 200, 200);
     scene.setItemIndexMethod(QGraphicsScene::NoIndex);
 
     for (int i = 0; i < MouseCount; ++i) {
         Mouse *mouse = new Mouse;
         mouse->setPos(::sin((i * 6.28) / MouseCount) * 200,
                       ::cos((i * 6.28) / MouseCount) * 200);
         scene.addItem(mouse);
     }
 
 
     //QGraphicsView view(&scene);
     game_view->setScene(&scene);
     //game_view->setRenderHint(QPainter::Antialiasing);
     //game_view->setBackgroundBrush(QPixmap(":/images/cheese.jpg"));
     //game_view->setCacheMode(QGraphicsView::CacheBackground);
     //game_view->setDragMode(QGraphicsView::ScrollHandDrag);
     //game_view->setWindowTitle(QT_TRANSLATE_NOOP(QGraphicsView, "Colliding Mice"));
     //game_view->resize(400, 300);
//game_view->show();
}

#include <QtGui> 
#include <QPrinter>
#include <QGraphicsScene>
#include <QStyleOption>
#include <math.h>
#include "myqtapp.h"

#include "mouse.h"

static const int MouseCount = 2;

myQtApp::myQtApp(QWidget*)
{
	setupUi(this);
	connect( pushButton_newgame, SIGNAL( clicked() ), this, SLOT( newgame() ) );
     QGraphicsScene scene;
     scene.setSceneRect(-100, -100, 200, 200);
     scene.setItemIndexMethod(QGraphicsScene::NoIndex);

     for (int i = 0; i < MouseCount; ++i) {
         Mouse *mouse = new Mouse;
         mouse->setPos(::sin((i * 6.28) / MouseCount) * 200,
                       ::cos((i * 6.28) / MouseCount) * 200);
         scene.addItem(mouse);
     }


     //QGraphicsView view(&scene);
     game_view->setScene(&scene);
     //game_view->setRenderHint(QPainter::Antialiasing);
     //game_view->setBackgroundBrush(QPixmap(":/images/cheese.jpg"));
     //game_view->setCacheMode(QGraphicsView::CacheBackground);
     //game_view->setDragMode(QGraphicsView::ScrollHandDrag);
     //game_view->setWindowTitle(QT_TRANSLATE_NOOP(QGraphicsView, "Colliding Mice"));
     //game_view->resize(400, 300);
//game_view->show();
}

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[Lykurg]

Yeah, it is exactly like I said. Your scene is deleted at the end of the constructor. So you can not expect to see something that already gets deleted. It's all about basic C++ knowledge: Live time of objects. Feel free to contact any c++ reference. And please use the code tags next time.

[procompmx5]

Thank you, found my issues and fixed them
Chris