Question about QGraphicsScene and QGraphicsPixmapItem

[CAP 33]

I want to do the following: when I click on the scene, an object Server is added to it at the coordinates of the mouse click and that object I can move.
In an object inherited from QGraphicsPixmapItem, defined mouseMoveEvent methods to move it. Everything is working. When I click on an object and move it with the mouse, the object also moves.
Next, I created a new class inherited from QGraphicsScene and defined the mousePressEvent method in it, which emits a click signal that takes the coordinates of the scene. In the main program, I implemented a slot that adds an object to the scene at the coordinates of the event. Connected signal and slot.
As a result of testing, it turned out that the object is added to the scene when you click on the scene. But it moves only when you double-click.
How do I make it move on one click?

class Server : public QGraphicsPixmapItem{
public:
    Server(QPoint);
    void mouseMoveEvent(QGraphicsSceneMouseEvent *event);
};
void Server::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{

    this->QGraphicsPixmapItem::setPos(QGraphicsPixmapItem::mapToScene(event->pos()));

class Field : public QGraphicsScene
{
    Q_OBJECT
public:
    Field();
    void mousePressEvent(QGraphicsSceneMouseEvent *event);

signals:
    void Press(QPoint);
};
void Field::mousePressEvent(QGraphicsSceneMouseEvent *event){
    emit Press((event->scenePos().toPoint()));
}

scene = new Field;
ui->graphicsView->setScene(scene);
connect(scene, SIGNAL(Press(QPoint)), this, SLOT(press_on_scene(QPoint)));

void MainWindow::press_on_scene(QPoint coordinate){
    if(ui->pushButton_2->isChecked()){
        Server *serv = new Server(coordinate);
        scene->addItem(serv);
    }
}

[JonB]

@CAP-33
I don't quite follow what you are saying with "But it moves only when you double-click." (I never seem to, unlike some responders here who are clairvoyant!). Are you saying it worked as you wanted to before you created a derived class? [Also your Server::mouseMoveEvent() method above is "chopped off".]

Anyway, in your mouseMoveEvent() overrides you do not call the base implementation. I always do that. Is that your problem?

[CAP 33]

@JonB
At first the scene was an object of the QGraphicsScene class, the QGraphicsScene::mousePressEvent method was not implemented and the Server moved around the scene with a single mouse click.
After I replaced the scene with an object of the Field class, in which I implemented the Field::mousePressEvent method, the Server can still move around the scene, but for some reason not with one mouse click, but with a double click.

[JonB]

@JonB said in Question about QGraphicsScene and QGraphicsPixmapItem:

Anyway, in your mouseMoveEvent() overrides you do not call the base implementation. I always do that. Is that your problem?

[CAP 33]

@JonB
No

[SGaist]

Hi,

Why not make your item movable ? That way you don't have to do any special handling.

[Pl45m4]

@CAP-33 said in Question about QGraphicsScene and QGraphicsPixmapItem:

But it moves only when you double-click.

Could be a focus issue. First click sets focus from scene to item, second activates the click and mouseMovement of your item.
But I would do what @SGaist suggested. If you make your item movable, you shouldn't face any problems

[CAP 33]

@Pl45m4
I have set the flag QGraphicsPixmapItem::setFlag(QGraphicsPixmapItem::ItemIsMovable, true), but it didn’t solve the problem.

[SGaist]

@CAP-33 did you remove your custom mouse handling ?

[CAP 33]

I solved my problem via event filter of scene.

ui->graphicsView->scene()->installEventFilter(this);

bool MainWindow::eventFilter(QObject* obj, QEvent* event){
    if(event->type() == QEvent::GraphicsSceneMousePress){
        if(ui->addServerBtn->isChecked()){
            QGraphicsSceneMouseEvent* mouseSceneEvent;
            mouseSceneEvent = static_cast<QGraphicsSceneMouseEvent *>(event);
            Server *serv = new Server(mouseSceneEvent->scenePos().toPoint());
            scene->addItem((QGraphicsPixmapItem*)serv);
        }
    }
return false;
}