效果图

讯享网
QWHArrowItem类头文件

#ifndef QWHARROWITEM_H #define QWHARROWITEM_H #include <QGraphicsLineItem> #include "qwhcircleitem.h" class QWHArrowItem : public QGraphicsLineItem { public: enum {Type = UserType}; explicit QWHArrowItem(QWHCircleItem *startItem, QWHCircleItem *endItem, QGraphicsItem *parent = nullptr); ~QWHArrowItem(); int type() const override; QRectF boundingRect() const override; QPainterPath shape() const override; protected: void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = nullptr) override; public: //位置更新 void updatePosition(); //获取起始Item QWHCircleItem *getStartItem(); //获取结束Item QWHCircleItem *getEndItem(); private: QWHCircleItem *m_startItem; //起始Item QWHCircleItem *m_endItem; //结束Item qreal m_arrowSize; //箭头大小 QColor m_lineColor; //线条颜色 QColor m_arrowColor; //箭头颜色 }; #endif // QWHARROWITEM_H 

QWHArrowItem类的核心代码

讯享网void QWHArrowItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) { Q_UNUSED(option) Q_UNUSED(widget) //碰撞时不绘制箭头 if (m_startItem->collidesWithItem(m_endItem)) return; //半径 int startItemRadius = m_startItem->radius(); int endItemRadius = m_endItem->radius(); //绘制箭头 double radians = qAcos(line().dx() / line().length()); if (line().dy() > 0) {//得到真正的弧度，qAcos函数返回的弧度在0-M_PI之间 radians = 2 * M_PI - radians; } radians += M_PI; //获取圆和直线的交点，箭头绘制在交点处，不绘制在圆心（直线末端） QPointF startPoint = line().p1() + QPointF(startItemRadius * qCos(radians + M_PI), -startItemRadius * qSin(radians + M_PI)); QPointF endPoint = line().p2() + QPointF(endItemRadius * qCos(radians), -endItemRadius * qSin(radians)); double radiusL = radians - qDegreesToRadians(30.0); //箭头左边线段，角度可变 double radiusR = radians + qDegreesToRadians(30.0); //箭头右边线段，角度可变 QPointF pointL = QPointF(endPoint.x() + m_arrowSize * qCos(radiusL), endPoint.y() - m_arrowSize * qSin(radiusL)); QPointF pointR = QPointF(endPoint.x() + m_arrowSize * qCos(radiusR), endPoint.y() - m_arrowSize * qSin(radiusR)); QLineF lineL = QLineF(endPoint, pointL); QLineF lineR = QLineF(endPoint, pointR); painter->setPen(QPen(m_lineColor, 2, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin)); painter->drawLine(startPoint, endPoint); QPainterPath path; path.moveTo(endPoint); path.lineTo(pointL); path.lineTo(pointR); painter->fillPath(path, m_arrowColor); } 

QWHCircleItem头文件

#ifndef QWHCIRCLEITEM_H #define QWHCIRCLEITEM_H #include <QGraphicsEllipseItem> class QWHArrowItem; class QWHCircleItem : public QGraphicsEllipseItem { public: enum {Type = UserType + 2}; explicit QWHCircleItem(QPointF pos, qreal radius, QGraphicsItem *parent = nullptr); ~QWHCircleItem(); int type() const override; public: //添加箭头 void addArrow(QWHArrowItem *arrow); //移除箭头 void removeArrow(QWHArrowItem *arrow); //移出所有箭头 void removeArrows(); //获取半径 qreal radius(); protected: //位置改变 QVariant itemChange(QGraphicsItem::GraphicsItemChange change, const QVariant &value) override; private: QList<QWHArrowItem *> m_arrows; //箭头集合 qreal m_radius; //半径 }; #endif // QWHCIRCLEITEM_H 

QWHCircleItem类的核心代码

讯享网void QWHCircleItem::removeArrows() { foreach (QWHArrowItem *arrow, m_arrows) { arrow->getStartItem()->removeArrow(arrow); arrow->getEndItem()->removeArrow(arrow); scene()->removeItem(arrow); delete arrow; } } QVariant QWHCircleItem::itemChange(QGraphicsItem::GraphicsItemChange change, const QVariant &value) { if (change == ItemPositionChange && scene()) { foreach (QWHArrowItem *arrow, m_arrows) arrow->updatePosition(); } return value; }