QCustomPlot长时间画实时曲线时总是曲线消失问题

galaxy_strive

于 2025-03-22 11:24:35 发布

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文章标签：命令模式 qt c++

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解决QCustomPlot长时间画实时曲线时总是曲线消失问题

盯了一天后，发现只要跨夜，曲线就会消失，经过查询资料可知，代码中使用 QTime::currentTime().msecsSinceStartOfDay() 来获取时间作为 x 轴的值，该方法返回的是从当天零点开始到当前时刻的毫秒数。当跨夜时，msecsSinceStartOfDay() 会重新从 0 开始计时，这就导致 x 轴的值会突然变小，进而使得之前绘制的曲线因为超出当前 x 轴显示范围而消失。

原部分代码

 qint64 currentTime = QTime::currentTime().msecsSinceStartOfDay()  / 1000.0;
double key = currentTime;
static double lastPointKey = 0;
double xMin = ui->customPlot->xAxis->range().lower;
double xMax = ui->customPlot->xAxis->range().upper;
upperLine->point1->setCoords(xMin, global::canshu[4].toDouble());
upperLine->point2->setCoords(xMax, global::canshu[4].toDouble());
downLine->point1->setCoords(xMin, global::canshu[3].toDouble());
downLine->point2->setCoords(xMax, global::canshu[3].toDouble());

更改后的代码：

void mainUI::initForm()
{
     ui->customPlot->addGraph();
     originalColor = QColor(qSin(2 * 1 + 1.2) * 80 + 80, qSin(2 * 0.3 + 0) * 80 + 80, qSin(2 * 0.3 + 1.5) * 80 + 80);
     ui->customPlot->graph(0)->setPen(QPen(originalColor));
     ui->customPlot->graph(0)->setLineStyle((QCPGraph::LineStyle)1);
     ui->customPlot->graph(0)->setScatterStyle(QCPScatterStyle(QCPScatterStyle::ssCircle, 5));
     // 添加上下限报警线
     upperLine = new QCPItemStraightLine(ui->customPlot);
     upperLine->setPen(QPen(Qt::red, 1, Qt::DashLine));
     downLine = new QCPItemStraightLine(ui->customPlot);
     downLine->setPen(QPen(Qt::red, 1, Qt::DashLine));

// 关键更改
     QSharedPointer<QCPAxisTickerDateTime> timeTicker(new QCPAxisTickerDateTime);
     // 关键更改
     timeTicker->setDateTimeFormat("HH:mm:ss");
     ui->customPlot->xAxis->setTicker(timeTicker);
     ui->customPlot->axisRect()->setupFullAxesBox();
     ui->customPlot->xAxis->setLabel("时间");
     ui->customPlot->yAxis->setLabel("流量m³/s");
     // 整个折线图标题
     QCPTextElement* PlotTitle = new QCPTextElement(ui->customPlot, "日期-流量实时曲线图");
     PlotTitle->setFont(QFont("宋体", 12, QFont::Bold)); // 设置标题的字体
     ui->customPlot->plotLayout()->insertRow(0);
     ui->customPlot->plotLayout()->addElement(0, 0, PlotTitle);
     connect(ui->customPlot->xAxis, SIGNAL(rangeChanged(QCPRange)), ui->customPlot->xAxis2, SLOT(setRange(QCPRange)));

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

     connect(&plotTimer, SIGNAL(timeout()), this, SLOT(realtimeDataSlot()));
}

void mainUI::realtimeDataSlot()
{
// 关键更改
    long long currentTime = QDateTime::currentMSecsSinceEpoch() / 1000.0;
    double key = currentTime;
    static double lastPointKey = 0;
    double xMin = ui->customPlot->xAxis->range().lower;
    double xMax = ui->customPlot->xAxis->range().upper;
    upperLine->point1->setCoords(xMin, global::canshu[4].toDouble());
    upperLine->point2->setCoords(xMax, global::canshu[4].toDouble());
    downLine->point1->setCoords(xMin, global::canshu[3].toDouble());
    downLine->point2->setCoords(xMax, global::canshu[3].toDouble());
    if (global::canshu[2]=="枯水期" && global::liuliang00 < global::canshu[3].toDouble())
    {
        ui->customPlot->graph(0)->setPen(QPen(Qt::red));
    }

    else if (global::canshu[2]=="丰水期" && global::liuliang00 < global::canshu[4].toDouble())
    {
        ui->customPlot->graph(0)->setPen(QPen(Qt::red));
    }
    else
    {
         ui->customPlot->graph(0)->setPen(QPen(originalColor));
    }

    // 两秒绘制一次数据
    if (key - lastPointKey >= 2)
    {
        ui->customPlot->graph(0)->addData(currentTime, global::liuliang00);
        recentData.append(global::liuliang00);
        if (recentData.size() > dataCount)
        {
            recentData.removeFirst();
        }
        lastPointKey = key;
    }

    // 动态调整纵坐标
    if (!recentData.isEmpty())
    {
        double minY = *std::min_element(recentData.begin(), recentData.end());
        double maxY = *std::max_element(recentData.begin(), recentData.end());
        double margin = qMax((maxY - minY) * 0.1, 0.1);
        static double lastMinY = 0.0, lastMaxY = 0.0;
        if (qAbs(minY - lastMinY) > 0.01 || qAbs(maxY-lastMaxY) > 0.01)
        {
            ui->customPlot->yAxis->setRange(minY - margin, maxY + margin);
            lastMinY = minY;
            lastMaxY = maxY;
        }
    }
    ui->customPlot->xAxis->setRange(key, 8, Qt::AlignRight);
    ui->customPlot->replot(QCustomPlot::rpQueuedReplot);
}