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QCustomPlot利用QCPItemStraightLine实现鼠标跟踪线

news 2026/5/12 18:39:40

实现原理:在QCustomPlot添加两个QCPItemStraightLine对象分别用于鼠标X\Y轴跟踪线绘制，重写QCustomPlot的鼠标移动事件并捕获鼠标实时坐标传递至QCPItemStraightLine更新位置，QCustomPlot重绘进行效果呈现。具体实现需要重写QCustomPlot方法及封装QCPItemStraightLine的功能类。

1、封装QCPItemStraightLine的功能类

  1 #ifndef MOUSETRACELINE_H
  2 #define MOUSETRACELINE_H
  3 #include "qcustomplot.h"
  4 #include <QObject>
  5 
  6 enum LineType
  7 {
  8     VerticalLine,   //垂直线
  9     HorizonLine,    //水平线
 10     Both            //同时显示水平和垂直线
 11 };
 12 
 13 class MouseTraceLine : public QObject
 14 {
 15     Q_OBJECT
 16 public:
 17     explicit MouseTraceLine(QCustomPlot *_plot, LineType _type = VerticalLine,QObject *parent = nullptr);
 18     ~MouseTraceLine();
 19 
 20     void init_line();
 21     void updatePosition(double xValue, double yValue);
 22 protected:
 23     bool m_visible;//是否可见
 24     LineType m_type;//类型
 25     QCustomPlot *m_plot;//图表
 26     QCPItemStraightLine *m_lineV; //垂直线
 27     QCPItemStraightLine *m_lineH; //水平线
 28 
 29 signals:
 30 
 31 public slots:
 32 };
 33 
 34 #endif // MOUSETRACELINE_H
 35 
 36 #include "mousetraceline.h"
 37 
 38 MouseTraceLine::MouseTraceLine(QCustomPlot *_plot, LineType _type,QObject *parent) : QObject(parent),
 39     m_type(_type),
 40     m_plot(_plot)
 41 {
 42     m_lineH = Q_NULLPTR;
 43     m_lineV = Q_NULLPTR;
 44     init_line();
 45 }
 46 
 47 MouseTraceLine::~MouseTraceLine()
 48 {
 49     if(m_plot)
 50     {
 51         if(m_lineH)
 52             m_plot->removeItem(m_lineH);
 53         if(m_lineV)
 54             m_plot->removeItem(m_lineV);
 55     }
 56 }
 57 
 58 void MouseTraceLine::init_line()
 59 {
 60     if(m_plot)
 61     {
 62         QPen linesPen(Qt::red, 1, Qt::DashLine);
 63         if(VerticalLine == m_type || Both == m_type)
 64         {
 65             m_lineV = new QCPItemStraightLine(m_plot);//垂直线
 66             m_lineV->setPen(linesPen);
 67             m_lineV->point1->setCoords(0, 0);
 68             m_lineV->point2->setCoords(0, 0);
 69         }
 70 
 71         if(HorizonLine == m_type || Both == m_type)
 72         {
 73             m_lineH = new QCPItemStraightLine(m_plot);//水平线
 74             m_lineH->setPen(linesPen);
 75             m_lineH->point1->setCoords(0, 0);
 76             m_lineH->point2->setCoords(0, 0);
 77         }
 78     }
 79 }
 80 
 81 void MouseTraceLine::updatePosition(double xValue, double yValue)
 82 {
 83     if(VerticalLine == m_type || Both == m_type)
 84     {
 85         if(m_lineV)
 86         {
 87             m_lineV->point1->setCoords(xValue, m_plot->yAxis->range().lower);
 88             m_lineV->point2->setCoords(xValue, m_plot->yAxis->range().upper);
 89         }
 90     }
 91 
 92     if(HorizonLine == m_type || Both == m_type)
 93     {
 94         if(m_lineH)
 95         {
 96             m_lineH->point1->setCoords(m_plot->xAxis->range().lower, yValue);
 97             m_lineH->point2->setCoords(m_plot->xAxis->range().upper, yValue);
 98         }
 99     }
100 }

2、QCustomPlot重写

 1 #ifndef QCUSTOMPLOTEX_H
 2 #define QCUSTOMPLOTEX_H
 3 
 4 #include "qcustomplot.h"
 5 #include "mousetraceline.h"
 6 class QCustomPlotEx : public QCustomPlot
 7 {
 8     Q_OBJECT
 9 public:
10     QCustomPlotEx();
11 
12 protected:
13     virtual void mouseMoveEvent(QMouseEvent *event);
14 
15 private:
16     MouseTraceLine  *m_lineTracer;//直线
17 };
18 
19 #endif // QCUSTOMPLOTEX_H
20 
21 
22 #include "qcustomplotex.h"
23 
24 QCustomPlotEx::QCustomPlotEx()
25 {
26     m_lineTracer = new MouseTraceLine(this,LineType::Both);
27 }
28 
29 void QCustomPlotEx::mouseMoveEvent(QMouseEvent *event)
30 {
31     QCustomPlot::mouseMoveEvent(event);
32     //当前鼠标位置（像素坐标）
33     int x_pos = event->pos().x();
34     int y_pos = event->pos().y();
35 
36     //像素坐标转成实际的x,y轴的坐标
37     double x_val = this->xAxis->pixelToCoord(x_pos);
38     double y_val = this->yAxis->pixelToCoord(y_pos);
39 
40     m_lineTracer->updatePosition(x_val, y_val);
41     this->replot();
42 }