QGraphicsView, QGraphicsScene and QGraphicsItem Problem :(

Hello Guys :)

Im very new in Qt and have a little Problem, maybe its not a Qt Problem or a thinking error.

Okay lets start ;)
I want to build a GUI that have a modular window architecture. I thought i create a QMainWindow and set a QGraphicsView as the centralWidget.
Now i create a MainScene and set it up to the View and in this Scene i have some buttons (QObejct and QGraphicsItem inherited).
When i click e.g. "ServiceButton" then i emit a Signal from the button to the scene and from the scene to the View.
Now i want to set a new Scene to the View, but first delete the old scene.

At this point my program crashes :/

i hope somebody understands me ;)

But my Problem is, that i don't know if this idear 100% would be work.

Here is my Hole Code:

Main.cpp:

Code:

---

#include <QtGui/QApplication>
#include "mainview.h"
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
 
    QMainWindow* wMain = new QMainWindow();
    MainView* mainView = new MainView();
    wMain->setWindowFlags(Qt::FramelessWindowHint);
    wMain->setCentralWidget(mainView);
    wMain->show();
 
    return a.exec();
}

---

MainView.cpp + .h:

Code:

---

#ifndef MAINVIEW_H
#define MAINVIEW_H
 
#include <QGraphicsView>
#include "mainscene.h"
#include "basicscene.h"
 
class MainView : public QGraphicsView
{
    Q_OBJECT
public:
 
    MainView(QWidget* parent = 0);
    ~MainView();
 
protected:
    void resizeEvent(QResizeEvent *event);
 
public slots:
    void createBasicScene();
    void createMainScene();
 
private:
    MainScene* m_mainScene;
    BasicScene* m_basicScene;
 
};
 
#endif // MAINVIEW_H
 
 
#include "mainview.h"
#include <QDebug>
#include <QMouseEvent>
#include <QtOpenGL/QtOpenGL>
 
 
MainView::MainView(QWidget* parent) : QGraphicsView(parent)
{
 
    qDebug() << "Start GraphicsView";
    setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    setGeometry(QRect(0,0,800,480));
 
    m_mainScene = new MainScene();
    m_mainScene->setSceneRect(QRectF(rect()));
 
    setScene(m_mainScene);
    setRenderHint(QPainter::Antialiasing);
    setViewport(new QGLWidget());
 
    connect(m_mainScene, SIGNAL(setBasicScene()), this, SLOT(createBasicScene()));
 
}
 
MainView::~MainView()
{
    delete m_mainScene;
    delete m_basicScene;
}
 
void MainView::resizeEvent(QResizeEvent *event)
{
    QGraphicsView::resizeEvent(event);
}
 
 
void MainView::createBasicScene()
{
    if(scene() != NULL)
        delete scene();
    m_basicScene = new BasicScene();
    setScene(m_basicScene);
    connect(m_basicScene, SIGNAL(setMainScene()), this, SLOT(createMainScene()));
}
 
void MainView::createMainScene()
{
    if(scene() != NULL)
        delete scene();
    m_mainScene = new MainScene();
    setScene(m_mainScene);
    connect(m_mainScene, SIGNAL(setBasicScene()), this, SLOT(createBasicScene()));
}

---

MainScene.cpp + .h:

Code:

---

#ifndef MAINSCENE_H
#define MAINSCENE_H
 
#include <QGraphicsScene>
#include <QDebug>
#include "roundrectitem.h"
#include <QGraphicsSceneMouseEvent>
 
class MainScene : public QGraphicsScene
{
    Q_OBJECT
public:
    MainScene(QObject* parent = 0);
    ~MainScene();
 
protected:
    void mousePressEvent(QGraphicsSceneMouseEvent *event);
 
 
public slots:
    void buttonService();
 
signals:
    void setBasicScene();
 
private:
    RoundRectItem* rect;
//    RoundRectItem* rect2;
//    RoundRectItem* rect3;
 
};
 
#endif // MAINSCENE_H
 
#include "mainscene.h"
 
 
MainScene::MainScene(QObject* parent) : QGraphicsScene(parent)
{
    setSceneRect(0,0,800,480);
    qDebug() << "Start MainScene";
    QRectF iconRect(-100, -100, 200, 200);
    QColor iconColor(214,240,110,128);
    rect = new RoundRectItem(iconRect, iconColor);
 
    rect->setObjectName("button");
 
    addItem(rect);
 
    rect->setPos(100,100);
 
    connect(rect, SIGNAL(clicked()), this, SLOT(buttonService()));
}
 
MainScene::~MainScene()
{
    //removeItem(rect);
    clear();
}
 
void MainScene::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
 
    QGraphicsScene::mousePressEvent(event);
    qDebug() << "MainScene: Pressed";
//    RoundRectItem* child = qgraphicsitem_cast<RoundRectItem*>( itemAt(event->scenePos()));
    //    if(!child)
    //        return;
 
}
 
 
void MainScene::buttonService()
{
    emit setBasicScene();
}

---

RoundRectItem.cpp + .h:

Code:

---

#ifndef ROUNDRECTITEM_H
#define ROUNDRECTITEM_H
 
#include <QGraphicsObject>
#include <QLinearGradient>
#include <QGraphicsDropShadowEffect>
#include <QPropertyAnimation>
#include <QGraphicsRotation>
#include <QGraphicsItem>
#include <QObject>
 
class RoundRectItem :  public QObject, public QGraphicsItem
{
    Q_OBJECT
    Q_PROPERTY(bool fill READ fill WRITE setFill)
public:
    RoundRectItem(const QRectF bounds, const QColor &color);
    ~RoundRectItem();
    QPixmap pixmap()const;
    void setPixmap(const QPixmap &pixmap);
 
    QRectF boundingRect() const;
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
 
    bool fill()const;
    void setFill(bool fill);
 
    QString objectName() const;
    void setObjectName(const QString &name);
 
protected:
    void mousePressEvent(QGraphicsSceneMouseEvent *event);
 
signals:
    void clicked();
 
 
 
private:
    QPixmap pix;
    bool fillRect;
    QRectF bounds;
    QLinearGradient gradient;
    QGraphicsDropShadowEffect* shadow;
    QString m_objectName;
 
 
};
 
#endif // ROUNDRECTITEM_H
 
#include "roundrectitem.h"
#include <QtGui>
#include <QDebug>
#include <QPainterPath>
 
RoundRectItem::RoundRectItem(const QRectF bounds, const QColor &color)
    :  QObject(0), QGraphicsItem(), fillRect(false), bounds(bounds)
{
    gradient.setStart(bounds.topLeft());
    gradient.setFinalStop(bounds.bottomRight());
    gradient.setColorAt(0, color);
    gradient.setColorAt(1, color.dark(200));
    setCacheMode(ItemCoordinateCache);
 
    shadow = new QGraphicsDropShadowEffect();
    shadow->setBlurRadius(50);
    shadow->setColor(QColor(0x40,0x40,0x40,255));
    setGraphicsEffect(shadow);
 
    m_objectName = "x";
 
}
 
RoundRectItem::~RoundRectItem()
{
    delete shadow;
}
 
 
QPixmap RoundRectItem::pixmap()const
{
    return pix;
}
 
void RoundRectItem::setPixmap(const QPixmap &pixmap)
{
    pix = pixmap;
 
    setFlags(flags() | QGraphicsItem::ItemIsSelectable);
    update();
}
 
void RoundRectItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    Q_UNUSED(option);
    Q_UNUSED(widget);
    painter->setPen(Qt::NoPen);
    painter->setBrush(QColor(0,0,0,64));
    painter->drawRoundRect(bounds.translated(2,2));
   // painter->drawRoundRect(bounds);
 
    if(fillRect)
        painter->setBrush(QApplication::palette().brush(QPalette::Window));
    else
        painter->setBrush(gradient);
    painter->setPen(QPen(Qt::black,1));
    painter->drawRoundRect(bounds);
 
    if(!pix.isNull())
    {
        painter->scale(1.95,1.95);
        painter->drawPixmap(-pix.width() /2, -pix.height()/2, pix);
    }
    else{
 
        QPainterPath* path = new QPainterPath();
        QFont serifFont("Times", 20, QFont::Bold);
        path->addText(bounds.center().x(),bounds.center().y(), serifFont, m_objectName);
        painter->drawPath(*path);
    }
}
 
bool RoundRectItem::fill() const
{
    return fillRect;
}
 
 
void RoundRectItem::setFill(bool fill)
{
    fillRect = fill;
    update();
}
 
QString RoundRectItem::objectName() const
{
    return m_objectName;
}
 
void RoundRectItem::setObjectName(const QString &name)
{
    m_objectName = name;
}
 
QRectF RoundRectItem::boundingRect()const
{
    return bounds.adjusted(0,0,2,2);
}
 
void RoundRectItem::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
 
   // QGraphicsItem::mousePressEvent(event);
    qDebug() << "RoundRectItem: Pressed";
    emit clicked();
 
}

---

The BasicScene is just Similar to MainScene.

Or can i made my idear in another way to change the scene's or Views?

Thank for Help :)

Best regards

nudels

so vielleicht?

Code:

---

connect(m_mainScene, SIGNAL(setBasicScene()), this, SLOT(createBasicScene()), Qt:QueedConnection);
 
 
 
if(scene() != NULL)
m_basicScene->deleteLater();
m_basicScene = new BasicScene();
setScene(m_basicScene);
connect(m_basicScene, SIGNAL(setMainScene()), this, SLOT(createMainScene()));

---

Hey dennis81,

thanks for ur reply :)

now i have solced my problem and get a new one :D
when i click on my scene then i get a debug output: "MainScene: Pressed". thats all right, but when i click now on a roundrectitem in the scene, then i get this output:
"RoundRectItem: Pressed
MainScene: Pressed"

but i dont want that the scene gets an MousePressEvent, because i just want to "press" the RoundRectItem.
How can i made this? do i need an eventFilter in the Scene?

And another question i have:
Is it better, when i make my own SceneItems like RoundRectitem, to inherit from QGraphicsItem or QGraphicsObject?

I ask, because when i inherit from QGraphicsItem and QObject and want to Animate like move in x-direction, then i need to create a new Q_PROPERTY. But when i inherit from QGraphicsObejct, then i have more defined Propertys, which i can animate.

Thanks for helping ;)

with best regards :)

nudels

Quote:

---

How can i made this? do i need an eventFilter in the Scene?

---

You can call event->accept() in rect item, and test if event->isAccepted() in scene mousePressEvent.
About your second question, I think you answered it yourself - if inheriting from QGraphicsItem requires you to do more work, isn't it better to use QGraphicsObject ?