QCustomPlot绘制动态曲线，鼠标悬停显示数据

要实现动态曲线的绘制和鼠标悬停显示数据，可以使用QCustomPlot库。

首先，创建一个QCustomPlot对象，并设置x轴和y轴的范围：

QCustomPlot *plot = new QCustomPlot(this);
plot->xAxis->setRange(0, 10);
plot->yAxis->setRange(-1, 1);

然后，添加一条曲线并设置其属性：

QCPGraph *graph = plot->addGraph();
graph->setPen(QPen(Qt::blue));
graph->setAntialiasedFill(false);

接下来，在定时器中不断更新曲线的数据，并调用replot()函数刷新图表：

QTimer *timer = new QTimer(this);
connect(timer, &QTimer::timeout, this, [plot, graph]() {
    static double phase = 0;
    QVector<double> x(101), y(101);
    for (int i = 0; i < 101; ++i) {
        x[i] = i / 10.0;
        y[i] = qSin(x[i]*2*M_PI + phase);
    }
    graph->setData(x, y);
    plot->replot();
    phase += 0.1;
});
timer->start(50);

最后，实现鼠标悬停显示数据的功能，可以使用QCPItemTracer类，它可以跟踪曲线上某个点的坐标，并在鼠标悬停时显示该点的数据：

QCPItemTracer *tracer = new QCPItemTracer(plot);
tracer->setGraph(graph);
tracer->setStyle(QCPItemTracer::tsCircle);
tracer->setPen(QPen(Qt::red));
tracer->setBrush(Qt::white);
tracer->setSize(10);
tracer->setVisible(false);

connect(plot, &QCustomPlot::mouseMove, this, [plot, tracer](QMouseEvent *event) {
    QPointF pos = plot->mapToValue(event->pos());
    double x = pos.x();
    double y = graph->data()->value(x);
    if (!qIsNaN(y)) {
        tracer->setVisible(true);
        tracer->setGraphKey(x);
        tracer->updatePosition();
        QString text = QString("x=%1, y=%2").arg(x).arg(y);
        QToolTip::showText(event->globalPos(), text, plot);
    } else {
        tracer->setVisible(false);
        QToolTip::hideText();
    }
});

完整的示例代码如下：

#include <QApplication>
#include <QMainWindow>
#include <QCustomPlot>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QMainWindow window;
    QCustomPlot *plot = new QCustomPlot(&window);
    plot->xAxis->setRange(0, 10);
    plot->yAxis->setRange(-1, 1);

    QCPGraph *graph = plot->addGraph();
    graph->setPen(QPen(Qt::blue));
    graph->setAntialiasedFill(false);

    QCPItemTracer *tracer = new QCPItemTracer(plot);
    tracer->setGraph(graph);
    tracer->setStyle(QCPItemTracer::tsCircle);
    tracer->setPen(QPen(Qt::red));
    tracer->setBrush(Qt::white);
    tracer->setSize(10);
    tracer->setVisible(false);

    connect(plot, &QCustomPlot::mouseMove, &window, [plot, tracer](QMouseEvent *event) {
        QPointF pos = plot->mapToValue(event->pos());
        double x = pos.x();
        double y = graph->data()->value(x);
        if (!qIsNaN(y)) {
            tracer->setVisible(true);
            tracer->setGraphKey(x);
            tracer->updatePosition();
            QString text = QString("x=%1, y=%2").arg(x).arg(y);
            QToolTip::showText(event->globalPos(), text, plot);
        } else {
            tracer->setVisible(false);
            QToolTip::hideText();
        }
    });

    QTimer *timer = new QTimer(&window);
    connect(timer, &QTimer::timeout, &window, [plot, graph]() {
        static double phase = 0;
        QVector<double> x(101), y(101);
        for (int i = 0; i < 101; ++i) {
            x[i] = i / 10.0;
            y[i] = qSin(x[i]*2*M_PI + phase);
        }
        graph->setData(x, y);
        plot->replot();
        phase += 0.1;
    });
    timer->start(50);

    window.setCentralWidget(plot);
    window.resize(800, 600);
    window.show();

    return a.exec();
}