How to override a function QGraphicsScene::items()

Mikeeeeee

Hi!
How to override a function QGraphicsScene::items()
I made a blank, but I do not understand what to do next

#include "QGraphicsScene"
#include "QObject"
#include "moveitem.h"
#include "QVector"


class MyQGraphicsScene : public QObject, public QGraphicsScene
{
    Q_OBJECT

public:
    MyQGraphicsScene();
    ~MyQGraphicsScene(){;}
    
public slots:
    QVector <MoveItem> myItems();

};

#include "myqgraphicsscene.h"

MyQGraphicsScene::MyQGraphicsScene()
{
    
}

QVector<MoveItem> MyQGraphicsScene::myItems()
{
    QVector<MoveItem> myVector;
    
    return  myVector;
}

mrjj

Hi
Its not virtual so you cant override it.

And why would you?

What is the reason you cant use the normal items() ?

I think you are trying to solve a problem the wrong way so, please
give details about the requirement that made you feel you needed your own
item() function.

Mikeeeeee

I created such a class and would like to refer to its ellements:

class MoveItem : public QObject, public QGraphicsItem
{
    Q_OBJECT
public:
    explicit MoveItem(QObject *parent = 0);
    ~MoveItem();
    int id;
    int width, height;
    QImage image;

    int getId() const;
    void setImageDark(int id);

signals:

private:
    QRectF boundingRect() const;
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
    void mouseMoveEvent(QGraphicsSceneMouseEvent *event);     //движение с нажатой кнопкой
    void mousePressEvent(QGraphicsSceneMouseEvent *event);    //нажатие кнопки
    void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);  //отпускание кнопки


public slots:
};

Christian Ehrlicher

And why can't you simply call QGraphicsScene::items() in there?

Mikeeeeee

I can, but I can't access my objects and use the function setImageDark(int id)

Mikeeeeee

Maybe you know how to get the text of the original function QGraphicsScene::items() ?

SGaist

Hi,

Might be silly question but since you are not using any feature of QObject in your MoveItem why make it a QObject ?

If you really need that, there's already an existing class called QGraphicsObject.

Next, if your scene is only composed of your MoveItem, then you can go through the list and cast each pointer to the correct class and do whatever you need with it.

mrjj

@mikeeeeee
Hi
When using items(),
you just have to cast to your own type to use any function you defined.
(if cast dont fail, it IS your type)

https://doc.qt.io/qt-5/qgraphicsitem.html#qgraphicsitem_cast

and please note it says

Reimplement the type() function

Mikeeeeee

As items() to cause my type?
I write such objects of the MoveItem class :
```
for (int i = 0; i< id1.size(); i++)
{
MoveItem *item = new MoveItem();
item->setPos(x1[i], y1[i]);
item->id = id1[i]; // set id
item->width = width1[i];
item->height = height1[i];
scene->addItem(item);
}

Class MoveItem :

class MoveItem : public QObject, public QGraphicsItem
{
Q_OBJECT
public:
explicit MoveItem(QObject *parent = 0);
~MoveItem();
int id;
int width, height;
QImage image;

int getId() const;
void setImageDark(int id);

signals:

private:
QRectF boundingRect() const;
void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
void mouseMoveEvent(QGraphicsSceneMouseEvent *event);
void mousePressEvent(QGraphicsSceneMouseEvent *event);
void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);

public slots:
};

Mikeeeeee

Maybe you know how to get the text of the original function QGraphicsScene::items() ?

SGaist

What text ?

Mikeeeeee

The function code itself. Apparently it can take a few alterations.

SGaist

You really are not clear.

wrosecrans

@mikeeeeee You don't need to modify items() or QGraphicsScene to do what you want. If you add your custom items to the scene, they will be in the list of items returned. Just have some other function where you iterate through the pointers to items to do what you want with the ones that are the type you are looking for. It's a very normal use case, and modifying QGraphicsScene to have an unusual behavior for items() is only going to make your life difficult.

Mikeeeeee

Added elements in vector and so was able to to them turn.