qcustomplot添加2个坐标系

在 QCustomPlot 中，添加 2 个坐标系需要以下步骤：

1. 创建第二个坐标系对象，使用 `QCPAxisRect` 类的 `addAxis` 方法添加第二个 x 轴和 y 轴。

// 创建第二个坐标系对象
QCPAxisRect *secondAxisRect = new QCPAxisRect(customPlot);
customPlot->plotLayout()->addElement(1, 0, secondAxisRect);
// 添加第二个 x 轴和 y 轴
QCPAxis *secondXAxis = secondAxisRect->addAxis(QCPAxis::atBottom);
QCPAxis *secondYAxis = secondAxisRect->addAxis(QCPAxis::atLeft);

2. 设置第二个坐标系的范围和标签，以及第二个 x 轴和 y 轴的属性。

// 设置第二个坐标系的范围和标签
secondAxisRect->setupFullAxesBox(true);
secondAxisRect->setRangeZoom(Qt::Horizontal);
secondAxisRect->setRangeDrag(Qt::Horizontal);
secondAxisRect->axis(QCPAxis::atBottom)->setLabel("Second X Axis");
secondAxisRect->axis(QCPAxis::atLeft)->setLabel("Second Y Axis");
// 设置第二个 x 轴和 y 轴的属性
secondXAxis->setTickLabels(false);
secondYAxis->setTickLabels(false);
secondXAxis->setTicks(false);
secondYAxis->setTicks(false);
secondXAxis->setRange(customPlot->xAxis->range());
secondYAxis->setRange(customPlot->yAxis->range());

3. 在绘制数据时，使用第二个坐标系的 x 轴和 y 轴。

// 绘制数据时使用第二个坐标系的 x 轴和 y 轴
graph1->setData(xData, yData);
graph1->rescaleAxes(false);
graph1->setPen(QPen(QColor(255, 0, 0)));
graph1->setName("Graph 1");
graph1->setSelectable(QCP::stSingleData);
graph1->setScatterStyle(QCPScatterStyle(QCPScatterStyle::ssCircle, 5));
graph1->addToLegend();
graph1->setVisible(true);
graph1->setLineStyle(QCPGraph::lsNone);
graph1->setScatterStyle(QCPScatterStyle(QCPScatterStyle::ssCircle, 5));
graph1->setPen(QPen(QColor(255, 0, 0)));
customPlot->addGraph(secondXAxis, secondYAxis);
graph2->setData(xData, yData2);
graph2->rescaleAxes(true);
graph2->setPen(QPen(QColor(0, 0, 255)));
graph2->setName("Graph 2");
graph2->setSelectable(QCP::stSingleData);
graph2->setScatterStyle(QCPScatterStyle(QCPScatterStyle::ssCircle, 5));
graph2->addToLegend();
graph2->setVisible(true);
graph2->setLineStyle(QCPGraph::lsNone);
graph2->setScatterStyle(QCPScatterStyle(QCPScatterStyle::ssCircle, 5));
graph2->setPen(QPen(QColor(0, 0, 255)));
customPlot->addGraph(secondXAxis, secondYAxis);

完整代码如下：

// 创建第二个坐标系对象
QCPAxisRect *secondAxisRect = new QCPAxisRect(customPlot);
customPlot->plotLayout()->addElement(1, 0, secondAxisRect);
// 添加第二个 x 轴和 y 轴
QCPAxis *secondXAxis = secondAxisRect->addAxis(QCPAxis::atBottom);
QCPAxis *secondYAxis = secondAxisRect->addAxis(QCPAxis::atLeft);

// 设置第二个坐标系的范围和标签
secondAxisRect->setupFullAxesBox(true);
secondAxisRect->setRangeZoom(Qt::Horizontal);
secondAxisRect->setRangeDrag(Qt::Horizontal);
secondAxisRect->axis(QCPAxis::atBottom)->setLabel("Second X Axis");
secondAxisRect->axis(QCPAxis::atLeft)->setLabel("Second Y Axis");
// 设置第二个 x 轴和 y 轴的属性
secondXAxis->setTickLabels(false);
secondYAxis->setTickLabels(false);
secondXAxis->setTicks(false);
secondYAxis->setTicks(false);
secondXAxis->setRange(customPlot->xAxis->range());
secondYAxis->setRange(customPlot->yAxis->range());

// 绘制数据时使用第二个坐标系的 x 轴和 y 轴
graph1->setData(xData, yData);
graph1->rescaleAxes(false);
graph1->setPen(QPen(QColor(255, 0, 0)));
graph1->setName("Graph 1");
graph1->setSelectable(QCP::stSingleData);
graph1->setScatterStyle(QCPScatterStyle(QCPScatterStyle::ssCircle, 5));
graph1->addToLegend();
graph1->setVisible(true);
graph1->setLineStyle(QCPGraph::lsNone);
graph1->setScatterStyle(QCPScatterStyle(QCPScatterStyle::ssCircle, 5));
graph1->setPen(QPen(QColor(255, 0, 0)));
customPlot->addGraph(secondXAxis, secondYAxis);
graph2->setData(xData, yData2);
graph2->rescaleAxes(true);
graph2->setPen(QPen(QColor(0, 0, 255)));
graph2->setName("Graph 2");
graph2->setSelectable(QCP::stSingleData);
graph2->setScatterStyle(QCPScatterStyle(QCPScatterStyle::ssCircle, 5));
graph2->addToLegend();
graph2->setVisible(true);
graph2->setLineStyle(QCPGraph::lsNone);
graph2->setScatterStyle(QCPScatterStyle(QCPScatterStyle::ssCircle, 5));
graph2->setPen(QPen(QColor(0, 0, 255)));
customPlot->addGraph(secondXAxis, secondYAxis);