QCustomplot 选择折线上的点并显示当前折线点的数值大小

本帖子原创作者：清澈的眼神@xiaoniede。转载注明原创作者地址。欢迎大家一起讨论技术问题。学习交流QQ群：498278174

     不多说直接上效果图：
图1：[attachment=15215]

图2：

图片:程序效果图2.png

实现思路参考qt Charts下例子：scatterinteractions。
void Dialog::initCustomplot(){    
     ///鼠标点击的有效距离，越小越准确。    
    ui->customplot->setSelectionTolerance(5);  
     ///设置用户交互
     ui->customplot->setInteractions(QCP::iRangeDrag     
                                                      | QCP::iRangeZoom                                     
                                                      | QCP::iMultiSelect                                     
                                                      | QCP::iSelectOther                                     
                                                      | QCP::iSelectItems                                     
                                                    /*| QCP::iSelectPlottables*/                                    
                                                      );
    ///set X Axis    
    ui->customplot->xAxis->setRange(0, 100);
    ///set Y Axis    
    ui->customplot->yAxis->setRange(-50, 50);    
    ui->customplot->yAxis->setAutoTickCount(2); ///设定自动显示的标签个数
    ///设置自动步长，方便区间控制    
    ui->customplot->yAxis->setAutoTickStep(false);    
    ui->customplot->yAxis->setTickStep(50.0);


    ///释放鼠标处理    
    connect(ui->customplot, SIGNAL(mouseRelease(QMouseEvent*)),
               this, SLOT(slot_mouseRelese(QMouseEvent*)));
    ///添加文本标签
    m_pMousValue = new QCPItemText(ui->customplot);    
    ui->customplot->addItem(m_pMousValue);    
    m_pMousValue->setPositionAlignment(Qt::AlignTop|Qt::AlignHCenter);    
    m_pMousValue->position->setType(QCPItemPosition::ptAxisRectRatio);    
    m_pMousValue->position->setCoords(0.5, 0); // place position at center/top of axis rect    
    m_pMousValue->setText("Text Item Value");    m_pMousValue->setFont(QFont(font().family(), 16)); // make font a bit larger    
    m_pMousValue->setPen(QPen(Qt::red)); // show black border around text
        ///具体思路如下：两条折线图，一条实线的折线图，一条散点的折线图    
        ui->customplot->addGraph();  
         ui->customplot->graph(0)->setPen(QPen(Qt::red, 2));    
         ui->customplot->graph(0)->setSelectedPen(QPen(Qt::blue, 2));    
          ui->customplot->graph(0)->setLineStyle(QCPGraph::lsLine);    ///步骤2 新建一条散点图    
          
          QCPScatterStyle myScatter;    
          myScatter.setShape(QCPScatterStyle::ssDisc);    
          myScatter.setPen(QPen(Qt::blue));    
          myScatter.setBrush(QBrush(Qt::white));    
          myScatter.setSize(5);    
          ui->customplot->addGraph();    
          ui->customplot->graph(1)->setLineStyle(QCPGraph::lsNone);    
          ui->customplot->graph(1)->setScatterStyle(myScatter);

    QVector<double> dVctValue;    
     QVector<double> dVctKeys;    
     int dequlNum = qrand()%10*50;    
     if(dequlNum == 0){        dequlNum = 50;    }  
     int n = 50;    
     for(int i = 0; i < n; i++)    {
        dVctValue.append(qrand()%dequlNum);        
        dVctKeys.append(i*2);  
     }    
     ui->customplot->graph(0)->clearData();    
     ui->customplot->graph(0)->addData(dVctKeys, dVctValue);    
     ui->customplot->graph(0)->rescaleValueAxis();
}

void Dialog::slot_mouseRelese(QMouseEvent *event){    
    ///排除非左鼠标键    
    if (event->button() != Qt::LeftButton){        return;    }
    
    QPointF ChickedPoint = event->posF();    
     ///排除区间外鼠标点    
    if(!ui->customplot->viewport().contains(event->pos())){        return;    }


    QPointF closest(INT_MAX, INT_MAX);    
     qreal distance(INT_MAX);
     QCPDataMap* m_graphDataMap1 = ui->customplot->graph(0)->data();    
     QCPDataMapIterator itr(*m_graphDataMap1);    
     while(itr.hasNext()){        
           itr.next();
          qreal dPosX = ui->customplot->xAxis->coordToPixel(itr.key());    
          qreal dPosY = ui->customplot->yAxis->coordToPixel(itr.value().value);


           QPointF currentPoint(dPosX, dPosY);
           qreal currentDistance = qSqrt((currentPoint.x()-ChickedPoint.x()) * (currentPoint.x()-ChickedPoint.x()) +  
                             (currentPoint.y()-ChickedPoint.y()) * (currentPoint.y()-ChickedPoint.y()));


        if(currentDistance < distance){
           distance = currentDistance;
           closest  = currentPoint;
        }
   }   
     ///可放开调试信息，观察鼠标点击到折线的距离。
    ///qDebug()<<"------pos-------"<<distance;    
    if(distance > ui->customplot->selectionTolerance()){        return;    }


     double dKey = ui->customplot->xAxis->pixelToCoord(closest.x());
     double dValue = ui->customplot->yAxis->pixelToCoord(closest.y());


    ///添加到散点折线图中
    ui->customplot->graph(1)->removeData(dKey);
    ui->customplot->graph(1)->addData(dKey, dValue);
    m_pMousValue->setText(QString("X: %1, Y: %2").arg(dKey).arg(dValue));
}

本帖子原创作者：清澈的眼神@xiaoniede。转载注明原创作者地址。欢迎大家一起讨论技术问题。学习交流QQ群：498278174