【QT Graphics/View】自定义动态同心圆DyConcentricCircle

一、功能

1、任意平移、改变内圆、外圆大小

2、鼠标中键切换箭头方向

3、获取圆心坐标，获取大小半径

4、鼠标移动到圆的边缘上改变鼠标形状

二、效果图

三、实现原理

1、图元组成及对应接口

2个圆圈

    painter->drawEllipse(rect1);painter->drawEllipse(rect2);

2条直线

    painter->drawLine(m_center.x() - m_radius, m_center.y(), m_center.x() - m_another_radius, m_center.y());painter->drawLine(m_center.x() + m_radius, m_center.y(), m_center.x() + m_another_radius, m_center.y());

2个箭头（一个箭头由2条直线组成）

2、判断鼠标在圆上

diff = 鼠标点与圆心的距离 - 圆的半径 

如果diff接近于0则认为鼠标在圆上

bool DyConcentricCircle::judgeInCircle(QPointF pos)
{QLineF line(m_center, pos);if(abs(line.length() - m_radius) < this->pen().widthF()){return true;}return false;
}

3、获取半径

并没有规定哪个半径为外半径，哪个半径为内半径，而是通过最大值、最小值确认的

外圆半径 = max(r1, r2)

内圆半径 = min(r1,r2)

double DyConcentricCircle::radiusInner() const
{return qMin(m_radius, m_another_radius);
}double DyConcentricCircle::radiusOuter() const
{return qMax(m_radius, m_another_radius);
}

四、关键代码

.h

#ifndef DYCONCENTRICCIRCLE_H
#define DYCONCENTRICCIRCLE_H#include "BaseGraphicsItem.h"class DyConcentricCircle : public BaseGraphicsItem
{Q_OBJECT
public:DyConcentricCircle(QPointF center, qreal radius1, qreal radius2,E_ItemType type = BaseGraphicsItem::E_ItemType::Dy_ConcentricCircle);double radiusInner() const;double radiusOuter() const;public:enum E_STATE_FLAG{DEFAULT_FLAG = 0,MOV_RADIUS,            /**< 第一个圆半径 */MOV_ANOTHER_RADIUS,    /**< 第二个圆半径 */};protected:virtual QRectF boundingRect() const override;virtual void paint(QPainter *painter,const QStyleOptionGraphicsItem *option,QWidget *widget) override;virtual void hoverEnterEvent(QGraphicsSceneHoverEvent *event) override;virtual void hoverMoveEvent(QGraphicsSceneHoverEvent *event) override;virtual void hoverLeaveEvent(QGraphicsSceneHoverEvent *event) override;virtual void mousePressEvent(QGraphicsSceneMouseEvent *event) override;virtual void mouseMoveEvent(QGraphicsSceneMouseEvent *event) override;virtual void mouseReleaseEvent(QGraphicsSceneMouseEvent *event) override;virtual void mouseDoubleClickEvent(QGraphicsSceneMouseEvent *event) override;private:/*** @brief judgeInCircle 是否在第一个圆上* @param pos* @return*/bool judgeInCircle(QPointF pos);/*** @brief judgeInAnotherArc 是否在第二个圆上* @param pos* @return*/bool judgeInAnotherCircle(QPointF pos);protected:qreal m_radius = 0;            /**< 第一个半径 */qreal m_another_radius = 0;    /**< 第二个半径 */E_STATE_FLAG m_stateFlag = DEFAULT_FLAG;
};#endif // DYCONCENTRICCIRCLE_H

.cpp

#include "DyConcentricCircle.h"
#include <QMenu>
#include <QSpinBox>
#include <QWidgetAction>
#include <QDebug>
#include <QComboBox>
#include <QCheckBox>
#include <QtMath>DyConcentricCircle::DyConcentricCircle(QPointF center, qreal radius1, qreal radius2, E_ItemType type): BaseGraphicsItem(center, type), m_radius(radius1),  m_another_radius(radius2)
{m_pointList.append(new DyPointItem(this, m_center, DyPointItem::Center));m_pointList.setRandColor();setAcceptHoverEvents(true);this->setFlags(QGraphicsItem::ItemIsSelectable | QGraphicsItem::ItemIsMovable | QGraphicsItem::ItemIsFocusable);
}double DyConcentricCircle::radiusInner() const
{return qMin(m_radius, m_another_radius);
}double DyConcentricCircle::radiusOuter() const
{return qMax(m_radius, m_another_radius);
}QRectF DyConcentricCircle::boundingRect() const
{qreal maxRadius = qMax(m_radius, m_another_radius);return QRectF(m_center.x() - maxRadius, m_center.y() - maxRadius, maxRadius * 2, maxRadius * 2);
}void DyConcentricCircle::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{Q_UNUSED(option);Q_UNUSED(widget);QPen pen = this->pen();double scaleFactor = painter->matrix().m11();pen.setWidthF(pen.widthF() / scaleFactor + 1);  /* 线段保持原来的线宽 */painter->setPen(pen);
//    QBrush brush(pen.color(), Qt::Dense1Pattern);
//    painter->setBrush(brush);painter->setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);/* 画圆 */QRectF rect1(m_center.x() - m_radius, m_center.y() - m_radius,m_radius * 2, m_radius * 2);QRectF rect2(m_center.x() - m_another_radius, m_center.y() - m_another_radius,m_another_radius * 2, m_another_radius * 2);painter->drawEllipse(rect1);painter->drawEllipse(rect2);/* 直线 */pen.setStyle(Qt::SolidLine);painter->setPen(pen);painter->drawLine(m_center.x() - m_radius, m_center.y(), m_center.x() - m_another_radius, m_center.y());painter->drawLine(m_center.x() + m_radius, m_center.y(), m_center.x() + m_another_radius, m_center.y());/* 箭头 */double arrowSize = 10;double arrowAngle = M_PI / 6;if(0 == m_direction){qreal radiusIn = radiusInner();/* 左箭头 */QPointF leftP(m_center.x() - radiusIn,  m_center.y());QPointF leftArrowP1;leftArrowP1.setX(m_center.x() - radiusIn - arrowSize * cos(arrowAngle));leftArrowP1.setY(m_center.y() - arrowSize * sin(arrowAngle));QPointF leftArrowP2;leftArrowP2.setX(m_center.x() - radiusIn - arrowSize * cos(arrowAngle));leftArrowP2.setY(m_center.y() + arrowSize * sin(arrowAngle));painter->drawLine(leftArrowP1, leftP);painter->drawLine(leftArrowP2, leftP);/* 右箭头 */QPointF rightP(m_center.x() + radiusIn,  m_center.y());QPointF rightArrowP1;rightArrowP1.setX(m_center.x() + radiusIn + arrowSize * cos(arrowAngle));rightArrowP1.setY(m_center.y() - arrowSize * sin(arrowAngle));QPointF rightArrowP2;rightArrowP2.setX(m_center.x() + radiusIn + arrowSize * cos(arrowAngle));rightArrowP2.setY(m_center.y() + arrowSize * sin(arrowAngle));painter->drawLine(rightArrowP1, rightP);painter->drawLine(rightArrowP2, rightP);}else{qreal radiusOut = radiusOuter();/* 左箭头 */QPointF leftP(m_center.x() - radiusOut,  m_center.y());QPointF leftArrowP1;leftArrowP1.setX(m_center.x() - radiusOut + arrowSize * cos(arrowAngle));leftArrowP1.setY(m_center.y() - arrowSize * sin(arrowAngle));QPointF leftArrowP2;leftArrowP2.setX(m_center.x() - radiusOut + arrowSize * cos(arrowAngle));leftArrowP2.setY(m_center.y() + arrowSize * sin(arrowAngle));painter->drawLine(leftArrowP1, leftP);painter->drawLine(leftArrowP2, leftP);/* 右箭头 */QPointF rightP(m_center.x() + radiusOut,  m_center.y());QPointF rightArrowP1;rightArrowP1.setX(m_center.x() + radiusOut - arrowSize * cos(arrowAngle));rightArrowP1.setY(m_center.y() - arrowSize * sin(arrowAngle));QPointF rightArrowP2;rightArrowP2.setX(m_center.x() + radiusOut - arrowSize * cos(arrowAngle));rightArrowP2.setY(m_center.y() + arrowSize * sin(arrowAngle));painter->drawLine(rightArrowP1, rightP);painter->drawLine(rightArrowP2, rightP);}
}void DyConcentricCircle::hoverEnterEvent(QGraphicsSceneHoverEvent *event)
{if(judgeInCircle(event->pos())){setCursor(Qt::CrossCursor);}else if (judgeInAnotherCircle(event->pos())){setCursor(Qt::CrossCursor);}else{setCursor(Qt::ArrowCursor);}event->accept();
}void DyConcentricCircle::hoverMoveEvent(QGraphicsSceneHoverEvent *event)
{if(judgeInCircle(event->pos())){setCursor(Qt::CrossCursor);}else if (judgeInAnotherCircle(event->pos())){setCursor(Qt::CrossCursor);}else{setCursor(Qt::ArrowCursor);}event->accept();
}void DyConcentricCircle::hoverLeaveEvent(QGraphicsSceneHoverEvent *event)
{setCursor(Qt::ArrowCursor);event->accept();
}void DyConcentricCircle::mousePressEvent(QGraphicsSceneMouseEvent *event)
{if(event->button() == Qt::LeftButton){if(judgeInCircle(event->pos())){m_stateFlag = MOV_RADIUS;}else if(judgeInAnotherCircle(event->pos())){m_stateFlag = MOV_ANOTHER_RADIUS;}}else if(event->button() == Qt::RightButton){}else if(event->button() == Qt::MiddleButton){/* 中键切换方向 */if(0 == m_direction){m_direction = 1;}else{m_direction = 0;}emit stateChanged(this);}QGraphicsItem::mousePressEvent(event);
}void DyConcentricCircle::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{switch (static_cast<int>(m_stateFlag)){case MOV_RADIUS:{/* 必须为pos，非scenePos*/QLineF line(m_center, event->pos());m_radius = line.length();break;}case MOV_ANOTHER_RADIUS:{QLineF line(m_center, event->pos());m_another_radius = line.length();break;}default:{QGraphicsItem::mouseMoveEvent(event);break;}}
}void DyConcentricCircle::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
{m_stateFlag = DEFAULT_FLAG;if(event->button() == Qt::LeftButton){emit stateChanged(this);}QGraphicsItem::mouseReleaseEvent(event);
}void DyConcentricCircle::mouseDoubleClickEvent(QGraphicsSceneMouseEvent *event)
{if(event->button() == Qt::LeftButton){emit selectCompleted(this);}QGraphicsItem::mouseDoubleClickEvent(event);
}bool DyConcentricCircle::judgeInCircle(QPointF pos)
{QLineF line(m_center, pos);if(abs(line.length() - m_radius) < this->pen().widthF()){return true;}return false;
}bool DyConcentricCircle::judgeInAnotherCircle(QPointF pos)
{QLineF line(m_center, pos);if(abs(line.length() - m_another_radius) < this->pen().widthF()){return true;}return false;
}