C++Qt不用UI界面的方式实现类似multisim中复制拖拽器件并且器件之间连接起来的功能的完整代码

在不使用UI界面的情况下实现类似Multisim中复制拖拽器件并且器件之间连接起来的功能，需要用到以下技术：

1. 继承QWidget类来实现自定义控件；
2. 用QGraphicsScene和QGraphicsView来实现绘图；
3. 用QGraphicsItem实现器件的拖拽和连接。

下面是一个简单的示例代码，实现了两个器件之间的连接和拖拽复制的功能：

#include <QApplication>
#include <QWidget>
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QGraphicsItem>
#include <QGraphicsEllipseItem>
#include <QGraphicsLineItem>
#include <QKeyEvent>
#include <QDebug>

class CircuitItem : public QGraphicsItem
{
public:
    CircuitItem(QGraphicsItem *parent = nullptr)
        : QGraphicsItem(parent)
    {
        setFlag(QGraphicsItem::ItemIsMovable, true);
        setFlag(QGraphicsItem::ItemIsSelectable, true);
    }

    QRectF boundingRect() const override
    {
        return QRectF(-25, -25, 50, 50);
    }

    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override
    {
        painter->setBrush(Qt::red);
        painter->drawEllipse(-25, -25, 50, 50);
    }

    void addWire(CircuitItem *other)
    {
        m_wires.append(other);
        other->m_wires.append(this);
        update();
        other->update();
    }

    void removeWire(CircuitItem *other)
    {
        m_wires.removeOne(other);
        other->m_wires.removeOne(this);
        update();
        other->update();
    }

    void removeAllWires()
    {
        for (CircuitItem *item : m_wires)
        {
            item->m_wires.removeOne(this);
            item->update();
        }
        m_wires.clear();
        update();
    }

    QVector<CircuitItem *> wires() const
    {
        return m_wires;
    }

protected:
    void mousePressEvent(QGraphicsSceneMouseEvent *event) override
    {
        if (event->button() == Qt::LeftButton)
        {
            m_dragStartPos = pos();
            m_isDragging = true;
            for (CircuitItem *item : m_wires)
            {
                item->removeWire(this);
            }
        }
        else if (event->button() == Qt::RightButton)
        {
            removeAllWires();
            scene()->removeItem(this);
            delete this;
        }
    }

    void mouseMoveEvent(QGraphicsSceneMouseEvent *event) override
    {
        if (m_isDragging)
        {
            setPos(m_dragStartPos + event->pos() - event->buttonDownPos(Qt::LeftButton));
            for (CircuitItem *item : m_wires)
            {
                item->update();
            }
        }
    }

    void mouseReleaseEvent(QGraphicsSceneMouseEvent *event) override
    {
        if (m_isDragging)
        {
            m_isDragging = false;
            for (QGraphicsItem *item : collidingItems())
            {
                CircuitItem *circuitItem = qgraphicsitem_cast<CircuitItem *>(item);
                if (circuitItem && circuitItem != this)
                {
                    addWire(circuitItem);
                }
            }
        }
    }

    void paintEvent(QPaintEvent *)
    {
        QPainter painter(this);
        paint(&painter, nullptr, nullptr);
    }

private:
    QPointF m_dragStartPos;
    bool m_isDragging = false;
    QVector<CircuitItem *> m_wires;
};

class CircuitScene : public QGraphicsScene
{
public:
    CircuitScene(QObject *parent = nullptr)
        : QGraphicsScene(parent)
    {
    }

protected:
    void keyPressEvent(QKeyEvent *event) override
    {
        if (event->key() == Qt::Key_C)
        {
            CircuitItem *item = new CircuitItem;
            addItem(item);
            item->setPos(0, 0);
        }
        else if (event->key() == Qt::Key_V)
        {
            QList<QGraphicsItem *> items = selectedItems();
            for (QGraphicsItem *item : items)
            {
                CircuitItem *circuitItem = qgraphicsitem_cast<CircuitItem *>(item);
                if (circuitItem)
                {
                    CircuitItem *copy = new CircuitItem;
                    addItem(copy);
                    copy->setPos(circuitItem->pos() + QPointF(50, 50));
                }
            }
        }
        else if (event->key() == Qt::Key_Delete)
        {
            QList<QGraphicsItem *> items = selectedItems();
            for (QGraphicsItem *item : items)
            {
                CircuitItem *circuitItem = qgraphicsitem_cast<CircuitItem *>(item);
                if (circuitItem)
                {
                    circuitItem->removeAllWires();
                    removeItem(circuitItem);
                    delete circuitItem;
                }
            }
        }
    }
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    CircuitScene scene;
    QGraphicsView view(&scene);
    view.setRenderHint(QPainter::Antialiasing);
    view.setBackgroundBrush(Qt::white);
    view.setDragMode(QGraphicsView::RubberBandDrag);
    view.show();

    return a.exec();
}

这个示例代码中，CircuitItem类继承自QGraphicsItem，实现了器件的拖拽和连接功能。CircuitScene类继承自QGraphicsScene，处理了键盘事件，实现了复制和删除器件的功能。在main函数中，创建了一个CircuitScene对象和一个QGraphicsView对象，将其显示出来。