qt c++重写继承QGraphicsView QGraphicsItem选中并改变颜色

可以通过重写QGraphicsItem的paint()函数来改变选中时的颜色，具体实现可以参考以下代码：

class MyGraphicsItem : public QGraphicsItem
{
public:
    MyGraphicsItem(QGraphicsItem *parent = nullptr) : QGraphicsItem(parent) {}

    QRectF boundingRect() const override
    {
        return QRectF(0, 0, 100, 100);
    }

    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override
    {
        if (option->state & QStyle::State_Selected)
        {
            painter->setPen(Qt::red);
            painter->setBrush(Qt::red);
        }
        else
        {
            painter->setPen(Qt::black);
            painter->setBrush(Qt::white);
        }

        painter->drawRect(boundingRect());
    }
};

class MyGraphicsView : public QGraphicsView
{
public:
    MyGraphicsView(QWidget *parent = nullptr) : QGraphicsView(parent)
    {
        setScene(new QGraphicsScene(this));
        MyGraphicsItem *item = new MyGraphicsItem;
        scene()->addItem(item);
    }

protected:
    void mousePressEvent(QMouseEvent *event) override
    {
        QGraphicsView::mousePressEvent(event);
        QGraphicsItem *item = scene()->itemAt(mapToScene(event->pos()), transform());
        if (item)
        {
            item->setSelected(true);
        }
    }
};

这里重写了MyGraphicsItem的paint()函数，在选中时将颜色设置为红色，未选中时设置为白色。在MyGraphicsView中重写了mousePressEvent()函数，当鼠标点击时获取当前位置的item并设置为选中状态。