QT QChartView 鼠标随动 十字线

QChart添加跟随鼠标的十字线_x县豆瓣酱的博客-CSDN博客_qchart鼠标跟踪线

最近在做这么一个东西，需要十字线。我参考自上面的博主的内容，但是他没写全。很多人不知道这个QGraphicsLineItem 是怎么创建的，然后x_line 和y_line 是如何弄到chartview 的Scene中的。

下面试我的效果，实现了：十字线随动，和放大缩小，平移拖动（鼠标中键-滚轮）。

缩放，平移拖动，参考了别的博主的代码。

这是我的效果。下面跟着代码。

qmychartview.h

#ifndef QMYCHARTVIEW_H
#define QMYCHARTVIEW_H
 
#include 
#include 
 
QT_CHARTS_USE_NAMESPACE
//using namespace QtCharts; // 这句和上面这句等价否则不认识 QChartView
class QMyChartView : public QChartView
{
    Q_OBJECT
public:
    QMyChartView(QWidget* pParent = nullptr);
    virtual ~QMyChartView();
protected:
     virtual void mouseMoveEvent(QMouseEvent *pEvent) override;
     virtual void mousePressEvent(QMouseEvent *pEvent) override;
     virtual void mouseReleaseEvent(QMouseEvent *pEvent) override;
     virtual void wheelEvent(QWheelEvent *pEvent) override;
     virtual void enterEvent(QEvent *pEvent)override;
     virtual void leaveEvent(QEvent *pEvent)override;
private:
     bool m_bMiddleButtonPressed;
     QPoint m_oPrePos;
     QGraphicsLineItem* x_line;
     QGraphicsLineItem* y_line;
     int m_oldPosOfX = 0;
signals:
     void sendXpos(int nPos);
 
};
 
#endif // QMYCHARTVIEW_H

 qmychartview.cpp

#include "qmychartview.h"
#include 
QMyChartView::QMyChartView(QWidget* pParent /*= nullptr*/):
    QChartView(pParent),
    m_bMiddleButtonPressed(false) ,
    m_oPrePos(0, 0)
{
    // 创建线
    x_line = new QGraphicsLineItem();
    // 设置颜色
    x_line->setPen(QPen(QColor( 100, 100, 100 )));
    x_line->setZValue(2);
    y_line = new QGraphicsLineItem();
    y_line->setPen(QPen(QColor( 100, 100, 100 )));
    y_line->setZValue(2);
    // 添加到scene中。
    this->scene()->addItem(x_line);
    this->scene()->addItem(y_line);
 
}
QMyChartView::~QMyChartView()
{
 
}
// 鼠标移动
void QMyChartView::mouseMoveEvent(QMouseEvent *pEvent)
{
    if (m_bMiddleButtonPressed)
    {
     QPoint oDeltaPos = pEvent->pos() - m_oPrePos;
     this->chart()->scroll(-oDeltaPos.x(), oDeltaPos.y());
     m_oPrePos = pEvent->pos();
 
    }
    //qDebug()<< this->chart()->mapToValue(pEvent->pos()).x();//把鼠标坐标值转化为画出的图中的坐标
    //qDebug() << "the x is :" << pEvent->pos().x() << " inchart :" << this->chart()->mapToValue(pEvent->pos());
    __super::mouseMoveEvent(pEvent);
 
    // 绘制线
    x_line->setLine(pEvent->x(),0,pEvent->x(),this->height());
    y_line->setLine(0,pEvent->y(),this->width(),pEvent->y());
 
    // 把x坐标发出去
    int nX = this->chart()->mapToValue(pEvent->pos()).x();
    if(nX != m_oldPosOfX){
        m_oldPosOfX = nX;
        emit sendXpos(m_oldPosOfX);
    }
}
 
// 鼠标按键
void QMyChartView::mousePressEvent(QMouseEvent *pEvent)
{
     if (pEvent->button() == Qt::MiddleButton)
     {
         m_bMiddleButtonPressed = true;
         m_oPrePos = pEvent->pos();
         this->setCursor(Qt::OpenHandCursor);
     }
     __super::mousePressEvent(pEvent);
}
// 鼠标抬起
void QMyChartView::mouseReleaseEvent(QMouseEvent *pEvent)
{
     if (pEvent->button() == Qt::MiddleButton)
     {
         m_bMiddleButtonPressed = false;
         this->setCursor(Qt::ArrowCursor);
     }
     __super::mouseReleaseEvent(pEvent);
}
 
void QMyChartView::wheelEvent(QWheelEvent *pEvent)
{
     qreal rVal = std::pow(0.999, pEvent->delta()); // 设置比例
     // 1. 读取视图基本信息
     QRectF oPlotAreaRect = this->chart()->plotArea();
     QPointF oCenterPoint = oPlotAreaRect.center();
     // 2. 水平调整
     oPlotAreaRect.setWidth(oPlotAreaRect.width() * rVal);
     // 3. 竖直调整
     oPlotAreaRect.setHeight(oPlotAreaRect.height() * rVal);
     // 4.1 计算视点，视点不变，围绕中心缩放
     //QPointF oNewCenterPoint(oCenterPoint);
     // 4.2 计算视点，让鼠标点击的位置移动到窗口中心
     //QPointF oNewCenterPoint(pEvent->pos());
     // 4.3 计算视点，让鼠标点击的位置尽量保持不动(等比换算，存在一点误差)
     QPointF oNewCenterPoint(2 * oCenterPoint - pEvent->pos() - (oCenterPoint - pEvent->pos()) / rVal);
     // 5. 设置视点
     oPlotAreaRect.moveCenter(oNewCenterPoint);
     // 6. 提交缩放调整
     this->chart()->zoomIn(oPlotAreaRect);
     __super::wheelEvent(pEvent);
}
 
void QMyChartView::enterEvent(QEvent *pEvent)
{
    x_line->setVisible(true);
    y_line->setVisible(true);
    __super::enterEvent(pEvent);
}
 
void QMyChartView::leaveEvent(QEvent *pEvent)
{
    x_line->setVisible(false);
    y_line->setVisible(false);
    __super::leaveEvent(pEvent);
}