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File myitem.h

#ifndef MYITEM_H
#define MYITEM_H
 
#include <QString>
 
class MyItem
{
public:
    virtual QString info ();
};
 
#endif // MYITEM_H

File myitem.cpp

#include "myitem.h"
 
QString MyItem::info ()
{
    return "my item";
}

File myrectangle.h

   #include "myitem.h"
   ... , public MyItem

#ifndef MYRECTANGLE_H
#define MYRECTANGLE_H
 
#include <QGraphicsRectItem>
#include "myitem.h"
 
class MyRectangle : public QGraphicsRectItem, public MyItem
{
public:
    virtual QString info ();
};
 
#endif // MYRECTANGLE_H

File myrectangle.cpp

#include "myrectangle.h"
 
QString MyRectangle::info ()
{
    return "my rectangle " +
            QString::number ( rect().x() ) + "," +
            QString::number ( rect().y() ) + " " +
            QString::number ( rect().width() ) + " x " +
            QString::number ( rect().height() );
}

File myellipse.h

   #include "myitem.h"
   ... , public MyItem

#ifndef MYELLIPSE_H
#define MYELLIPSE_H
 
#include <QGraphicsRectItem>
#include "myitem.h"
 
class MyEllipse : public QGraphicsRectItem, public MyItem
{
public:
    virtual QString info ();
};
 
#endif // MYELLIPSE_H

File myellipse.cpp

#include "myellipse.h"
 
QString MyEllipse::info ()
{
    return "my ellipse " +
            QString::number ( rect().x() ) + "," +
            QString::number ( rect().y() ) + " " +
            QString::number ( rect().width() ) + " x " +
            QString::number ( rect().height() );
}

File mywindow.cpp

#include "myrectangle.h"
#include "myellipse.h"

upravit ve funkci setup

    MyRectangle * r = new MyRectangle;
    MyEllipse * e = new MyEllipse;

pridat do funkce showBranch

    MyItem * m = dynamic_cast < MyItem * > (item);
    if (m != NULL)
        s = m->info ();

a cely soubor

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
#include <QGraphicsRectItem>
#include <QGraphicsEllipseItem>
 
#include "myrectangle.h"
 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    setup ();
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::setup ()
{
    QGraphicsScene * scene = new QGraphicsScene ();
    ui->graphicsView->setScene (scene);
 
    scene->addLine(10, 10, 100, 100);
    scene->addRect(100, 10, 20, 20);
    scene->addEllipse(140, 20, 40, 70);
 
    MyRectangle * r = new MyRectangle;
    r->setPen(QColor ("red"));
    r->setBrush(QColor ("yellow"));
    r->setRect (100, 100, 100, 100);
    r->setFlags(QGraphicsItem::ItemIsMovable);
    scene->addItem (r);
 
 
    for (int i = 1; i <= 2; i++)
    {
    QGraphicsEllipseItem * e = new QGraphicsEllipseItem;
    e->setPen(QColor ("orange"));
    e->setBrush(QColor ("green"));
    e->setParentItem (r);
    e->setRect (70 + 40*i, 120, 20, 20);
    }
 
    showScene (scene);
}
 
void MainWindow::showScene (QGraphicsScene * scene)
{
    QList < QGraphicsItem * > list = scene->items ();
    int cnt = list.count ();
    for (int i = 0 ; i < cnt; i++)
    {
        QGraphicsItem * p = list.value (i);
        if (p->parentItem() == NULL)
            showBranch (NULL, p);
    }
}
 
void MainWindow::showBranch (QTreeWidgetItem * above, QGraphicsItem * item)
{
    QTreeWidgetItem * t = new QTreeWidgetItem;
 
    QString s = "something";
 
    QGraphicsRectItem * r = dynamic_cast < QGraphicsRectItem * > (item);
    if (r != NULL)
        s = "rectangle " + QString::number ( r->rect().x() ) +
             ", " + QString::number ( r->rect().y() );
 
    MyRectangle * m = dynamic_cast < MyRectangle * > (item);
    if (m != NULL)
        s = m->info ();
 
    t->setText (0, s);
 
    if (above == NULL)
        ui->treeWidget->addTopLevelItem(t);
    else
        above->addChild (t);
 
 
    QList < QGraphicsItem * > list = item->childItems();
    int cnt = list.count ();
    for (int i = 0 ; i < cnt; i++)
        showBranch (t, list[i]);
}