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）

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

#ifndef MYTRACER_H

#define MYTRACER_H

#include <QObject>

#include "qcustomplot.h"

///

/// \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

///

class XxwTracer : public QObject

{

Q_OBJECT

public:

enum TracerType

{

        XAxisTracer,//依附在x轴上显示x值

        YAxisTracer,//依附在y轴上显示y值

        DataTracer//在图中显示x,y值

};

    explicit XxwTracer(QCustomPlot *_plot, TracerType _type, QObject *parent = Q_NULLPTR);

    ~XxwTracer();

void setPen(const QPen &pen);

void setBrush(const QBrush &brush);

void setText(const QString &text);

void setLabelPen(const QPen &pen);

void updatePosition(double xValue, double yValue);

    void setVisible(bool m_visible);

protected:

    bool m_visible;//是否可见

    TracerType m_type;//类型

    QCustomPlot *m_plot;//图表

    QCPItemTracer *m_tracer;//跟踪的点

    QCPItemText *m_label;//显示的数值

    QCPItemLine *m_arrow;//箭头

};

///

/// \brief The XxwCrossLine class:用于显示鼠标移动过程中的鼠标位置的直线

///

class XxwTraceLine : public QObject

{

public:

    enum LineType

    {

        VerticalLine,//垂直线

        HorizonLine, //水平线

        Both//同时显示水平和垂直线

    };

    explicit XxwTraceLine(QCustomPlot *_plot, LineType _type = VerticalLine, QObject *parent = Q_NULLPTR);

    ~XxwTraceLine();

    void initLine();

    void updatePosition(double xValue, double yValue);

    void setVisible(bool vis)

    {

        if(m_lineV)

            m_lineV->setVisible(vis);

        if(m_lineH)

            m_lineH->setVisible(vis);

    }

protected:

    bool m_visible;//是否可见

    LineType m_type;//类型

    QCustomPlot *m_plot;//图表

    QCPItemStraightLine *m_lineV; //垂直线

    QCPItemStraightLine *m_lineH; //水平线

};

#endif // MYTRACER_H

源文件MyTracer.cpp

#include "MyTracer.h"

XxwTracer::XxwTracer(QCustomPlot *_plot, TracerType _type, QObject *parent)

    : QObject(parent),

      m_plot(_plot),

      m_type(_type)

{

    m_visible = true;

    m_tracer = Q_NULLPTR;// 跟踪的点

    m_label = Q_NULLPTR;// 显示的数值

    m_arrow = Q_NULLPTR;// 箭头

    if (m_plot)

    {

        QColor clrDefault(Qt::red);

        QBrush brushDefault(Qt::NoBrush);

        QPen penDefault(clrDefault);

        //        penDefault.setBrush(brushDefault);

        penDefault.setWidthF(0.5);

        m_tracer = new QCPItemTracer(m_plot);

        m_tracer->setStyle(QCPItemTracer::tsCircle);

        m_tracer->setPen(penDefault);

        m_tracer->setBrush(brushDefault);

        m_label = new QCPItemText(m_plot);

        m_label->setLayer("overlay");

        m_label->setClipToAxisRect(false);

        m_label->setPadding(QMargins(, , , ));

        m_label->setBrush(brushDefault);

        m_label->setPen(penDefault);

        m_label->position->setParentAnchor(m_tracer->position);

//        m_label->setFont(QFont("宋体", 8));

        m_label->setFont(QFont("Arial", ));

        m_label->setColor(clrDefault);

        m_label->setText("");

        m_arrow = new QCPItemLine(m_plot);

        QPen  arrowPen(clrDefault, );

        m_arrow->setPen(penDefault);

        m_arrow->setLayer("overlay");

        m_arrow->setClipToAxisRect(false);

        m_arrow->setHead(QCPLineEnding::esSpikeArrow);//设置头部为箭头形状

        switch (m_type)

        {

        case XAxisTracer:

        {

            m_tracer->position->setTypeX(QCPItemPosition::ptPlotCoords);

            m_tracer->position->setTypeY(QCPItemPosition::ptAxisRectRatio);

            m_tracer->setSize();

            m_label->setPositionAlignment(Qt::AlignTop | Qt::AlignHCenter);

            m_arrow->end->setParentAnchor(m_tracer->position);

            m_arrow->start->setParentAnchor(m_arrow->end);

            m_arrow->start->setCoords(, );//偏移量

            break;

        }

        case YAxisTracer:

        {

            m_tracer->position->setTypeX(QCPItemPosition::ptAxisRectRatio);

            m_tracer->position->setTypeY(QCPItemPosition::ptPlotCoords);

            m_tracer->setSize();

            m_label->setPositionAlignment(Qt::AlignRight | Qt::AlignHCenter);

            m_arrow->end->setParentAnchor(m_tracer->position);

            m_arrow->start->setParentAnchor(m_label->position);

            m_arrow->start->setCoords(-, );//偏移量

            break;

        }

        case DataTracer:

        {

            m_tracer->position->setTypeX(QCPItemPosition::ptPlotCoords);

            m_tracer->position->setTypeY(QCPItemPosition::ptPlotCoords);

            m_tracer->setSize();

            m_label->setPositionAlignment(Qt::AlignLeft | Qt::AlignVCenter);

            m_arrow->end->setParentAnchor(m_tracer->position);

            m_arrow->start->setParentAnchor(m_arrow->end);

            m_arrow->start->setCoords(, );

            break;

        }

        default:

            break;

        }

        setVisible(false);

    }

}

XxwTracer::~XxwTracer()

{

    if(m_plot)

    {

        if (m_tracer)

            m_plot->removeItem(m_tracer);

        if (m_label)

            m_plot->removeItem(m_label);

        if (m_arrow)

            m_plot->removeItem(m_arrow);

    }

}

void XxwTracer::setPen(const QPen &pen)

{

    if(m_tracer)

        m_tracer->setPen(pen);

    if(m_arrow)

        m_arrow->setPen(pen);

}

void XxwTracer::setBrush(const QBrush &brush)

{

    if(m_tracer)

        m_tracer->setBrush(brush);

}

void XxwTracer::setLabelPen(const QPen &pen)

{

    if(m_label)

    {

        m_label->setPen(pen);

        m_label->setBrush(Qt::NoBrush);

        m_label->setColor(pen.color());

    }

}

void XxwTracer::setText(const QString &text)

{

    if(m_label)

        m_label->setText(text);

}

void XxwTracer::setVisible(bool vis)

{

    m_visible = vis;

    if(m_tracer)

        m_tracer->setVisible(m_visible);

    if(m_label)

        m_label->setVisible(m_visible);

    if(m_arrow)

        m_arrow->setVisible(m_visible);

}

void XxwTracer::updatePosition(double xValue, double yValue)

{

    if (!m_visible)

    {

        setVisible(true);

        m_visible = true;

    }

    if (yValue > m_plot->yAxis->range().upper)

        yValue = m_plot->yAxis->range().upper;

    switch (m_type)

    {

    case XAxisTracer:

    {

        m_tracer->position->setCoords(xValue, );

        m_label->position->setCoords(, );

        m_arrow->start->setCoords(, );

        m_arrow->end->setCoords(, );

        setText(QString::number(xValue));

        break;

    }

    case YAxisTracer:

    {

        m_tracer->position->setCoords(, yValue);

        m_label->position->setCoords(-, );

//        m_arrow->start->setCoords(20, 0);

//        m_arrow->end->setCoords(0, 0);

        setText(QString::number(yValue));

        break;

    }

    case DataTracer:

    {

        m_tracer->position->setCoords(xValue, yValue);

        m_label->position->setCoords(, );

        setText(QString("x:%1,y:%2").arg(xValue).arg(yValue));

        break;

    }

    default:

        break;

    }

}

XxwTraceLine::XxwTraceLine(QCustomPlot *_plot, LineType _type, QObject *parent)

    : QObject(parent),

      m_type(_type),

      m_plot(_plot)

{

    m_lineV = Q_NULLPTR;

    m_lineH = Q_NULLPTR;

    initLine();

}

XxwTraceLine::~XxwTraceLine()

{

    if(m_plot)

    {

        if (m_lineV)

            m_plot->removeItem(m_lineV);

        if (m_lineH)

            m_plot->removeItem(m_lineH);

    }

}

void XxwTraceLine::initLine()

{

    if(m_plot)

    {

        QPen linesPen(Qt::red, , Qt::DashLine);

        if(VerticalLine == m_type || Both == m_type)

        {

            m_lineV = new QCPItemStraightLine(m_plot);//垂直线

            m_lineV->setLayer("overlay");

            m_lineV->setPen(linesPen);

            m_lineV->setClipToAxisRect(true);

            m_lineV->point1->setCoords(, );

            m_lineV->point2->setCoords(, );

        }

        if(HorizonLine == m_type || Both == m_type)

        {

            m_lineH = new QCPItemStraightLine(m_plot);//水平线

            m_lineH->setLayer("overlay");

            m_lineH->setPen(linesPen);

            m_lineH->setClipToAxisRect(true);

            m_lineH->point1->setCoords(, );

            m_lineH->point2->setCoords(, );

        }

    }

}

void XxwTraceLine::updatePosition(double xValue, double yValue)

{

    if(VerticalLine == m_type || Both == m_type)

    {

        if(m_lineV)

        {

            m_lineV->point1->setCoords(xValue, m_plot->yAxis->range().lower);

            m_lineV->point2->setCoords(xValue, m_plot->yAxis->range().upper);

        }

    }

    if(HorizonLine == m_type || Both == m_type)

    {

        if(m_lineH)

        {

            m_lineH->point1->setCoords(m_plot->xAxis->range().lower, yValue);

            m_lineH->point2->setCoords(m_plot->xAxis->range().upper, yValue);

        }

    }

}

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

#ifndef XCUSTOMPLOT_H

#define XCUSTOMPLOT_H

#include "XxwTracer.h"

#include "qcustomplot.h"

#include <QObject>

#include <QList>

class XxwCustomPlot:public QCustomPlot

{

    Q_OBJECT

public:

    XxwCustomPlot(QWidget *parent = );

protected:

    virtual void mouseMoveEvent(QMouseEvent *event);

public:

    ///

    /// \brief 设置是否显示鼠标追踪器

    /// \param show:是否显示

    ///

    void showTracer(bool show)

    {

        m_isShowTracer = show;

        if(m_xTracer)

            m_xTracer->setVisible(m_isShowTracer);

        foreach (XxwTracer *tracer, m_dataTracers)

        {

            if(tracer)

                tracer->setVisible(m_isShowTracer);

        }

        if(m_lineTracer)

            m_lineTracer->setVisible(m_isShowTracer);

    }

    ///

    /// \brief 是否显示鼠标追踪器

    /// \return

    ///

    bool isShowTracer(){return m_isShowTracer;};

private:

    bool m_isShowTracer;//是否显示追踪器（鼠标在图中移动，显示对应的值）

    XxwTracer *m_xTracer;//x轴

    XxwTracer *m_yTracer;//y轴

    QList<XxwTracer *> m_dataTracers;//

    XxwTraceLine  *m_lineTracer;//直线

};

#endif // XCUSTOMPLOT_H

源文件XCustomPlot.h

#include "XxwCustomPlot.h"

XxwCustomPlot::XxwCustomPlot(QWidget *parent)

    :QCustomPlot(parent)

    ,m_isShowTracer(false)

    ,m_xTracer(Q_NULLPTR)

    ,m_yTracer(Q_NULLPTR)

    ,m_dataTracers(QList<XxwTracer *>())

    ,m_lineTracer(Q_NULLPTR)

{

}

void XxwCustomPlot::mouseMoveEvent(QMouseEvent *event)

{

    QCustomPlot::mouseMoveEvent(event);

    if(m_isShowTracer)

    {

        //当前鼠标位置（像素坐标）

        int x_pos = event->pos().x();

        int y_pos = event->pos().y();

        //像素坐标转成实际的x,y轴的坐标

        float x_val = this->xAxis->pixelToCoord(x_pos);

        float y_val = this->yAxis->pixelToCoord(y_pos);

        if(Q_NULLPTR == m_xTracer)

            m_xTracer = new XxwTracer(this, XxwTracer::XAxisTracer);//x轴

        m_xTracer->updatePosition(x_val, y_val);

        if(Q_NULLPTR == m_yTracer)

            m_yTracer = new XxwTracer(this, XxwTracer::YAxisTracer);//y轴

        m_yTracer->updatePosition(x_val, y_val);

        int nTracerCount = m_dataTracers.count();

        int nGraphCount = graphCount();

        if(nTracerCount < nGraphCount)

        {

            for(int i = nTracerCount; i < nGraphCount; ++i)

            {

                XxwTracer *tracer = new XxwTracer(this, XxwTracer::DataTracer);

                m_dataTracers.append(tracer);

            }

        }

        else if(nTracerCount > nGraphCount)

        {

            for(int i = nGraphCount; i < nTracerCount; ++i)

            {

                XxwTracer *tracer = m_dataTracers[i];

                if(tracer)

                {

                    tracer->setVisible(false);

                }

            }

        }

        for (int i = ; i < nGraphCount; ++i)

        {

            XxwTracer *tracer = m_dataTracers[i];

            if(!tracer)

                tracer = new XxwTracer(this, XxwTracer::DataTracer);

            tracer->setVisible(true);

            tracer->setPen(this->graph(i)->pen());

            tracer->setBrush(Qt::NoBrush);

            tracer->setLabelPen(this->graph(i)->pen());

            auto iter = this->graph(i)->data()->findBegin(x_val);

            double value = iter->mainValue();

//            double value = this->graph(i)->data()->findBegin(x_val)->value;

            tracer->updatePosition(x_val, value);

        }

        if(Q_NULLPTR == m_lineTracer)

            m_lineTracer = new XxwTraceLine(this,XxwTraceLine::Both);//直线

        m_lineTracer->updatePosition(x_val, y_val);

        this->replot();//曲线重绘

    }

}

3 使用自定义图表类XCustomPlot

在需要绘图的地方使用，代码如下：

  m_customPlot = new XxwCustomPlot();

    m_customPlot->showTracer(true);

    // add title layout element:

    m_customPlot->plotLayout()->insertRow();

    m_customPlot->plotLayout()->addElement(, , new QCPTextElement(m_customPlot, "标题", QFont("黑体", , QFont::Bold)));

    m_customPlot->legend->setVisible(true);

    QFont legendFont = font();  // start out with MainWindow's font..

    legendFont.setPointSize(); // and make a bit smaller for legend

    m_customPlot->legend->setFont(legendFont);

    m_customPlot->legend->setBrush(QBrush(QColor(,,,)));

    // 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:

    m_customPlot->axisRect()->insetLayout()->setInsetAlignment(, Qt::AlignTop|Qt::AlignCenter);

    // make left and bottom axes always transfer their ranges to right and top axes:

    connect(m_customPlot->xAxis, SIGNAL(rangeChanged(QCPRange)), m_customPlot->xAxis2, SLOT(setRange(QCPRange)));

    connect(m_customPlot->yAxis, SIGNAL(rangeChanged(QCPRange)), m_customPlot->yAxis2, SLOT(setRange(QCPRange)));

    // Allow user to drag axis ranges with mouse, zoom with mouse wheel and select graphs by clicking:

    m_customPlot->setInteractions(QCP::iRangeDrag | QCP::iRangeZoom | QCP::iSelectPlottables);

    // generate some data:

    int nCount = ;

    QVector<double> x(nCount), y0(nCount), y1(nCount); // initialize with entries 0..100

    for (int i = ; i < nCount; ++i)

    {

        x[i] = i; // x goes from -1 to 1

        y0[i] = qSin(i * 10.0f / nCount); //sin

        y1[i] = qCos(i * 10.0f / nCount); //cos

    }

    // create graph and assign data to it:

    QPen pen;

    int i = ;

    QCPGraph *pGraph = m_customPlot->addGraph();

    //        m_customPlot->graph(0)->setData(x, y0);

    pGraph->setName("sin曲线");

    pGraph->setData(x,y0);

    pGraph->setPen(QPen(Qt::blue));

    pGraph = m_customPlot->addGraph();

    //        m_customPlot->graph(0)->setData(x, y0);

    pGraph->setName("cos曲线");

    pGraph->setData(x,y1);

    pGraph->setPen(QPen(Qt::darkYellow));

    // give the axes some labels:

    m_customPlot->xAxis->setLabel("x");

    m_customPlot->yAxis->setLabel("y");

    // set axes ranges, so we see all data:

//    m_customPlot->xAxis->setRange(-1, 1);

//    m_customPlot->yAxis->setRange(0, 1);

    m_customPlot->rescaleAxes(true);

    m_customPlot->replot();

4 效果图

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

参考：https://blog.csdn.net/sunnyloves/article/details/82344815

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）

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）的相关教程结束。

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