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采用Qt快速绘制多条曲线（折线），跟随鼠标动态显示线上点的值（基于Qt的开源绘图控件QCustomPlot进行二次开发）
来源：cnblogs　　作者：先之　　时间：2018/12/12 9:54:32　　对本文有异议
QCustomPlot是一个开源的基于Qt的第三方绘图库，能够绘制漂亮的2D图形。
QCustomPlot的官方网址：https://www.qcustomplot.com/
从官网下载QCustomPlot的源文件，包括qcustomplot.h和qcustomplot.cpp。
 
本程序的源码下载地址： https://github.com/xiongxw/XCustomPlot.git
 
 
1 自定义鼠标显示跟随类XxwTracer和XxwTraceLine：
XxwTracer用于在图表中显示鼠标所在位置的x,y值
XxwTraceLine用于在图中显示水平或垂直的虚线
头文件XxwTracer.h
  1. #ifndef MYTRACER_H
  2. #define MYTRACER_H
  4. #include <QObject>
  5. #include "qcustomplot.h"
  7. ///
  8. /// \brief The XxwTracer class:在图表中显示鼠标所在位置的x,y值的追踪显示器
  9. ///
  10. class XxwTracer : public QObject
  11. {
  12. Q_OBJECT
  14. public:
  15. enum TracerType
  16. {
  17.         XAxisTracer,//依附在x轴上显示x值
  18.         YAxisTracer,//依附在y轴上显示y值
  19.         DataTracer//在图中显示x,y值
  20. };
  21.     explicit XxwTracer(QCustomPlot *_plot, TracerType _type, QObject *parent = Q_NULLPTR);
  22.     ~XxwTracer();
  23. void setPen(const QPen &pen);
  24. void setBrush(const QBrush &brush);
  25. void setText(const QString &text);
  26. void setLabelPen(const QPen &pen);
  27. void updatePosition(double xValue, double yValue);
  28.     void setVisible(bool m_visible);
  30. protected:
  31.     bool m_visible;//是否可见
  32.     TracerType m_type;//类型
  33.     QCustomPlot *m_plot;//图表
  34.     QCPItemTracer *m_tracer;//跟踪的点
  35.     QCPItemText *m_label;//显示的数值
  36.     QCPItemLine *m_arrow;//箭头
  37. };
  40. ///
  41. /// \brief The XxwCrossLine class:用于显示鼠标移动过程中的鼠标位置的直线
  42. ///
  43. class XxwTraceLine : public QObject
  44. {
  45. public:
  46.     enum LineType
  47.     {
  48.         VerticalLine,//垂直线
  49.         HorizonLine, //水平线
  50.         Both//同时显示水平和垂直线
  51.     };
  52.     explicit XxwTraceLine(QCustomPlot *_plot, LineType _type = VerticalLine, QObject *parent = Q_NULLPTR);
  53.     ~XxwTraceLine();
  54.     void initLine();
  55.     void updatePosition(double xValue, double yValue);
  57.     void setVisible(bool vis)
  58.     {
  59.         if(m_lineV)
  60.             m_lineV->setVisible(vis);
  61.         if(m_lineH)
  62.             m_lineH->setVisible(vis);
  63.     }
  65. protected:
  66.     bool m_visible;//是否可见
  67.     LineType m_type;//类型
  68.     QCustomPlot *m_plot;//图表
  69.     QCPItemStraightLine *m_lineV; //垂直线
  70.     QCPItemStraightLine *m_lineH; //水平线
  71. };
  73. #endif // MYTRACER_H

源文件MyTracer.cpp

  1. #include "MyTracer.h"
  3. XxwTracer::XxwTracer(QCustomPlot *_plot, TracerType _type, QObject *parent)
  4.     : QObject(parent),
  5.       m_plot(_plot),
  6.       m_type(_type)
  7. {
  8.     m_visible = true;
  9.     m_tracer = Q_NULLPTR;// 跟踪的点
  10.     m_label = Q_NULLPTR;// 显示的数值
  11.     m_arrow = Q_NULLPTR;// 箭头
  12.     if (m_plot)
  13.     {
  14.         QColor clrDefault(Qt::red);
  15.         QBrush brushDefault(Qt::NoBrush);
  16.         QPen penDefault(clrDefault);
  17.         //        penDefault.setBrush(brushDefault);
  18.         penDefault.setWidthF(0.5);
  20.         m_tracer = new QCPItemTracer(m_plot);
  21.         m_tracer->setStyle(QCPItemTracer::tsCircle);
  22.         m_tracer->setPen(penDefault);
  23.         m_tracer->setBrush(brushDefault);
  25.         m_label = new QCPItemText(m_plot);
  26.         m_label->setLayer("overlay");
  27.         m_label->setClipToAxisRect(false);
  28.         m_label->setPadding(QMargins(5, 5, 5, 5));
  29.         m_label->setBrush(brushDefault);
  30.         m_label->setPen(penDefault);
  31.         m_label->position->setParentAnchor(m_tracer->position);
  32. //        m_label->setFont(QFont("宋体", 8));
  33.         m_label->setFont(QFont("Arial", 8));
  34.         m_label->setColor(clrDefault);
  35.         m_label->setText("");
  37.         m_arrow = new QCPItemLine(m_plot);
  38.         QPen  arrowPen(clrDefault, 1);
  39.         m_arrow->setPen(penDefault);
  40.         m_arrow->setLayer("overlay");
  41.         m_arrow->setClipToAxisRect(false);
  42.         m_arrow->setHead(QCPLineEnding::esSpikeArrow);//设置头部为箭头形状
  44.         switch (m_type)
  45.         {
  46.         case XAxisTracer:
  47.         {
  48.             m_tracer->position->setTypeX(QCPItemPosition::ptPlotCoords);
  49.             m_tracer->position->setTypeY(QCPItemPosition::ptAxisRectRatio);
  50.             m_tracer->setSize(7);
  51.             m_label->setPositionAlignment(Qt::AlignTop | Qt::AlignHCenter);
  53.             m_arrow->end->setParentAnchor(m_tracer->position);
  54.             m_arrow->start->setParentAnchor(m_arrow->end);
  55.             m_arrow->start->setCoords(0, 20);//偏移量
  56.             break;
  57.         }
  58.         case YAxisTracer:
  59.         {
  60.             m_tracer->position->setTypeX(QCPItemPosition::ptAxisRectRatio);
  61.             m_tracer->position->setTypeY(QCPItemPosition::ptPlotCoords);
  62.             m_tracer->setSize(7);
  63.             m_label->setPositionAlignment(Qt::AlignRight | Qt::AlignHCenter);
  65.             m_arrow->end->setParentAnchor(m_tracer->position);
  66.             m_arrow->start->setParentAnchor(m_label->position);
  67.             m_arrow->start->setCoords(-20, 0);//偏移量
  68.             break;
  69.         }
  70.         case DataTracer:
  71.         {
  72.             m_tracer->position->setTypeX(QCPItemPosition::ptPlotCoords);
  73.             m_tracer->position->setTypeY(QCPItemPosition::ptPlotCoords);
  74.             m_tracer->setSize(5);
  76.             m_label->setPositionAlignment(Qt::AlignLeft | Qt::AlignVCenter);
  78.             m_arrow->end->setParentAnchor(m_tracer->position);
  79.             m_arrow->start->setParentAnchor(m_arrow->end);
  80.             m_arrow->start->setCoords(20, 0);
  81.             break;
  82.         }
  83.         default:
  84.             break;
  85.         }
  86.         setVisible(false);
  87.     }
  88. }
  90. XxwTracer::~XxwTracer()
  91. {
  92.     if(m_plot)
  93.     {
  94.         if (m_tracer)
  95.             m_plot->removeItem(m_tracer);
  96.         if (m_label)
  97.             m_plot->removeItem(m_label);
  98.         if (m_arrow)
  99.             m_plot->removeItem(m_arrow);
  100.     }
  101. }
  103. void XxwTracer::setPen(const QPen &pen)
  104. {
  105.     if(m_tracer)
  106.         m_tracer->setPen(pen);
  107.     if(m_arrow)
  108.         m_arrow->setPen(pen);
  109. }
  111. void XxwTracer::setBrush(const QBrush &brush)
  112. {
  113.     if(m_tracer)
  114.         m_tracer->setBrush(brush);
  115. }
  117. void XxwTracer::setLabelPen(const QPen &pen)
  118. {
  119.     if(m_label)
  120.     {
  121.         m_label->setPen(pen);
  122.         m_label->setBrush(Qt::NoBrush);
  123.         m_label->setColor(pen.color());
  124.     }
  125. }
  127. void XxwTracer::setText(const QString &text)
  128. {
  129.     if(m_label)
  130.         m_label->setText(text);
  131. }
  133. void XxwTracer::setVisible(bool vis)
  134. {
  135.     m_visible = vis;
  136.     if(m_tracer)
  137.         m_tracer->setVisible(m_visible);
  138.     if(m_label)
  139.         m_label->setVisible(m_visible);
  140.     if(m_arrow)
  141.         m_arrow->setVisible(m_visible);
  142. }
  144. void XxwTracer::updatePosition(double xValue, double yValue)
  145. {
  146.     if (!m_visible)
  147.     {
  148.         setVisible(true);
  149.         m_visible = true;
  150.     }
  152.     if (yValue > m_plot->yAxis->range().upper)
  153.         yValue = m_plot->yAxis->range().upper;
  155.     switch (m_type)
  156.     {
  157.     case XAxisTracer:
  158.     {
  159.         m_tracer->position->setCoords(xValue, 1);
  160.         m_label->position->setCoords(0, 15);
  161.         m_arrow->start->setCoords(0, 15);
  162.         m_arrow->end->setCoords(0, 0);
  163.         setText(QString::number(xValue));
  164.         break;
  165.     }
  166.     case YAxisTracer:
  167.     {
  168.         m_tracer->position->setCoords(0, yValue);
  169.         m_label->position->setCoords(-20, 0);
  170. //        m_arrow->start->setCoords(20, 0);
  171. //        m_arrow->end->setCoords(0, 0);
  172.         setText(QString::number(yValue));
  173.         break;
  174.     }
  175.     case DataTracer:
  176.     {
  177.         m_tracer->position->setCoords(xValue, yValue);
  178.         m_label->position->setCoords(20, 0);
  179.         setText(QString("x:%1,y:%2").arg(xValue).arg(yValue));
  180.         break;
  181.     }
  182.     default:
  183.         break;
  184.     }
  185. }
  187. XxwTraceLine::XxwTraceLine(QCustomPlot *_plot, LineType _type, QObject *parent)
  188.     : QObject(parent),
  189.       m_type(_type),
  190.       m_plot(_plot)
  191. {
  192.     m_lineV = Q_NULLPTR;
  193.     m_lineH = Q_NULLPTR;
  194.     initLine();
  195. }
  197. XxwTraceLine::~XxwTraceLine()
  198. {
  199.     if(m_plot)
  200.     {
  201.         if (m_lineV)
  202.             m_plot->removeItem(m_lineV);
  203.         if (m_lineH)
  204.             m_plot->removeItem(m_lineH);
  205.     }
  206. }
  208. void XxwTraceLine::initLine()
  209. {
  210.     if(m_plot)
  211.     {
  212.         QPen linesPen(Qt::red, 1, Qt::DashLine);
  214.         if(VerticalLine == m_type || Both == m_type)
  215.         {
  216.             m_lineV = new QCPItemStraightLine(m_plot);//垂直线
  217.             m_lineV->setLayer("overlay");
  218.             m_lineV->setPen(linesPen);
  219.             m_lineV->setClipToAxisRect(true);
  220.             m_lineV->point1->setCoords(0, 0);
  221.             m_lineV->point2->setCoords(0, 0);
  222.         }
  224.         if(HorizonLine == m_type || Both == m_type)
  225.         {
  226.             m_lineH = new QCPItemStraightLine(m_plot);//水平线
  227.             m_lineH->setLayer("overlay");
  228.             m_lineH->setPen(linesPen);
  229.             m_lineH->setClipToAxisRect(true);
  230.             m_lineH->point1->setCoords(0, 0);
  231.             m_lineH->point2->setCoords(0, 0);
  232.         }
  233.     }
  234. }
  236. void XxwTraceLine::updatePosition(double xValue, double yValue)
  237. {
  238.     if(VerticalLine == m_type || Both == m_type)
  239.     {
  240.         if(m_lineV)
  241.         {
  242.             m_lineV->point1->setCoords(xValue, m_plot->yAxis->range().lower);
  243.             m_lineV->point2->setCoords(xValue, m_plot->yAxis->range().upper);
  244.         }
  245.     }
  247.     if(HorizonLine == m_type || Both == m_type)
  248.     {
  249.         if(m_lineH)
  250.         {
  251.             m_lineH->point1->setCoords(m_plot->xAxis->range().lower, yValue);
  252.             m_lineH->point2->setCoords(m_plot->xAxis->range().upper, yValue);
  253.         }
  254.     }
  255. }

 

2 自定义的图表类XCustomPlot
XCustomPlot是基于QCustomPlot二次开发的图表类，在鼠标移动过程中动态显示曲线上点的值。
头文件XCustomPlot.h
  1. #ifndef XCUSTOMPLOT_H
  2. #define XCUSTOMPLOT_H
  4. #include "XxwTracer.h"
  5. #include "qcustomplot.h"
  6. #include <QObject>
  7. #include <QList>
  8.  
  9. class XxwCustomPlot:public QCustomPlot
  10. {
  11.     Q_OBJECT
  13. public:
  14.     XxwCustomPlot(QWidget *parent = 0);
  16. protected:
  17.     virtual void mouseMoveEvent(QMouseEvent *event);
  19. public:
  20.     ///
  21.     /// \brief 设置是否显示鼠标追踪器
  22.     /// \param show:是否显示
  23.     ///
  24.     void showTracer(bool show)
  25.     {
  26.         m_isShowTracer = show;
  27.         if(m_xTracer)
  28.             m_xTracer->setVisible(m_isShowTracer);
  29.         foreach (XxwTracer *tracer, m_dataTracers)
  30.         {
  31.             if(tracer)
  32.                 tracer->setVisible(m_isShowTracer);
  33.         }
  34.         if(m_lineTracer)
  35.             m_lineTracer->setVisible(m_isShowTracer);
  36.     }
  38.     ///
  39.     /// \brief 是否显示鼠标追踪器
  40.     /// \return
  41.     ///
  42.     bool isShowTracer(){return m_isShowTracer;};
  44. private:
  45.     bool m_isShowTracer;//是否显示追踪器（鼠标在图中移动，显示对应的值）
  46.     XxwTracer *m_xTracer;//x轴
  47.     XxwTracer *m_yTracer;//y轴
  48.     QList<XxwTracer *> m_dataTracers;//
  49.     XxwTraceLine  *m_lineTracer;//直线
  50. };
  52. #endif // XCUSTOMPLOT_H

源文件XCustomPlot.h

  1. #include "XxwCustomPlot.h"
  3. XxwCustomPlot::XxwCustomPlot(QWidget *parent)
  4.     :QCustomPlot(parent)
  5.     ,m_isShowTracer(false)
  6.     ,m_xTracer(Q_NULLPTR)
  7.     ,m_yTracer(Q_NULLPTR)
  8.     ,m_dataTracers(QList<XxwTracer *>())
  9.     ,m_lineTracer(Q_NULLPTR)
  10. {
  11. }
  13. void XxwCustomPlot::mouseMoveEvent(QMouseEvent *event)
  14. {
  15.     QCustomPlot::mouseMoveEvent(event);
  17.     if(m_isShowTracer)
  18.     {
  19.         //当前鼠标位置（像素坐标）
  20.         int x_pos = event->pos().x();
  21.         int y_pos = event->pos().y();
  23.         //像素坐标转成实际的x,y轴的坐标
  24.         float x_val = this->xAxis->pixelToCoord(x_pos);
  25.         float y_val = this->yAxis->pixelToCoord(y_pos);
  27.         if(Q_NULLPTR == m_xTracer)
  28.             m_xTracer = new XxwTracer(this, XxwTracer::XAxisTracer);//x轴
  29.         m_xTracer->updatePosition(x_val, y_val);
  31.         if(Q_NULLPTR == m_yTracer)
  32.             m_yTracer = new XxwTracer(this, XxwTracer::YAxisTracer);//y轴
  33.         m_yTracer->updatePosition(x_val, y_val);
  35.         int nTracerCount = m_dataTracers.count();
  36.         int nGraphCount = graphCount();
  37.         if(nTracerCount < nGraphCount)
  38.         {
  39.             for(int i = nTracerCount; i < nGraphCount; ++i)
  40.             {
  41.                 XxwTracer *tracer = new XxwTracer(this, XxwTracer::DataTracer);
  42.                 m_dataTracers.append(tracer);
  43.             }
  44.         }
  45.         else if(nTracerCount > nGraphCount)
  46.         {
  47.             for(int i = nGraphCount; i < nTracerCount; ++i)
  48.             {
  49.                 XxwTracer *tracer = m_dataTracers[i];
  50.                 if(tracer)
  51.                 {
  52.                     tracer->setVisible(false);
  53.                 }
  54.             }
  55.         }
  56.         for (int i = 0; i < nGraphCount; ++i)
  57.         {
  58.             XxwTracer *tracer = m_dataTracers[i];
  59.             if(!tracer)
  60.                 tracer = new XxwTracer(this, XxwTracer::DataTracer);
  61.             tracer->setVisible(true);
  62.             tracer->setPen(this->graph(i)->pen());
  63.             tracer->setBrush(Qt::NoBrush);
  64.             tracer->setLabelPen(this->graph(i)->pen());
  65.             auto iter = this->graph(i)->data()->findBegin(x_val);
  66.             double value = iter->mainValue();
  67. //            double value = this->graph(i)->data()->findBegin(x_val)->value;
  68.             tracer->updatePosition(x_val, value);
  69.         }
  71.         if(Q_NULLPTR == m_lineTracer)
  72.             m_lineTracer = new XxwTraceLine(this,XxwTraceLine::Both);//直线
  73.         m_lineTracer->updatePosition(x_val, y_val);
  75.         this->replot();//曲线重绘
  76.     }
  77. }

 

 

 

3 使用自定义图表类XCustomPlot

在需要绘图的地方使用，代码如下：

 

  1.   m_customPlot = new XxwCustomPlot();
  2.     m_customPlot->showTracer(true);
  4.     // add title layout element:
  5.     m_customPlot->plotLayout()->insertRow(0);
  6.     m_customPlot->plotLayout()->addElement(0, 0, new QCPTextElement(m_customPlot, "标题", QFont("黑体", 12, QFont::Bold)));
  8.     m_customPlot->legend->setVisible(true);
  9.     QFont legendFont = font();  // start out with MainWindow's font..
  10.     legendFont.setPointSize(9); // and make a bit smaller for legend
  11.     m_customPlot->legend->setFont(legendFont);
  12.     m_customPlot->legend->setBrush(QBrush(QColor(255,255,255,230)));
  13.     // by default, the legend is in the inset layout of the main axis rect. So this is how we access it to change legend placement:
  14.     m_customPlot->axisRect()->insetLayout()->setInsetAlignment(0, Qt::AlignTop|Qt::AlignCenter);
  16.     // make left and bottom axes always transfer their ranges to right and top axes:
  17.     connect(m_customPlot->xAxis, SIGNAL(rangeChanged(QCPRange)), m_customPlot->xAxis2, SLOT(setRange(QCPRange)));
  18.     connect(m_customPlot->yAxis, SIGNAL(rangeChanged(QCPRange)), m_customPlot->yAxis2, SLOT(setRange(QCPRange)));
  20.     // Allow user to drag axis ranges with mouse, zoom with mouse wheel and select graphs by clicking:
  21.     m_customPlot->setInteractions(QCP::iRangeDrag | QCP::iRangeZoom | QCP::iSelectPlottables);
  23.     // generate some data:
  24.     int nCount = 100;
  25.     QVector<double> x(nCount), y0(nCount), y1(nCount); // initialize with entries 0..100
  26.     for (int i = 0; i < nCount; ++i)
  27.     {
  28.         x[i] = i; // x goes from -1 to 1
  29.         y0[i] = qSin(i * 10.0f / nCount); //sin
  30.         y1[i] = qCos(i * 10.0f / nCount); //cos
  31.     }
  32.     // create graph and assign data to it:
  33.     QPen pen;
  34.     int i = 1;
  35.     QCPGraph *pGraph = m_customPlot->addGraph();
  36.     //        m_customPlot->graph(0)->setData(x, y0);
  37.     pGraph->setName("sin曲线");
  38.     pGraph->setData(x,y0);
  39.     pGraph->setPen(QPen(Qt::blue));
  41.     pGraph = m_customPlot->addGraph();
  42.     //        m_customPlot->graph(0)->setData(x, y0);
  43.     pGraph->setName("cos曲线");
  44.     pGraph->setData(x,y1);
  45.     pGraph->setPen(QPen(Qt::darkYellow));
  47.     // give the axes some labels:
  48.     m_customPlot->xAxis->setLabel("x");
  49.     m_customPlot->yAxis->setLabel("y");
  51.     // set axes ranges, so we see all data:
  52. //    m_customPlot->xAxis->setRange(-1, 1);
  53. //    m_customPlot->yAxis->setRange(0, 1);
  54.     m_customPlot->rescaleAxes(true);
  56.     m_customPlot->replot();

 

4 效果图

 
本程序的源码下载地址： https://github.com/xiongxw/XCustomPlot.git

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