qcustomplot饼状图

QCustomPlot是一个基于Qt框架的开源图表库，支持绘制多种类型的图表，包括饼状图。下介绍如何使用QCustomPlot绘制饼图：

1. 首先，在Qt项目中添加QCustomPlot库，并在代码中包含头文件。

2. 创建一个QCustomPlot对象，并设置其大小和标题。

QCustomPlot *customPlot = new QCustomPlot(this);
customPlot->setFixedSize(400, 400);
customPlot->plotLayout()->insertRow(0);
customPlot->plotLayout()->addElement(0, 0, new QCPTextElement(customPlot, "Pie Chart", QFont("sans", 12, QFont::Bold)));

3. 创建一个QPieChart对象，并设置其数据和颜色。

QPieChart *pieChart = new QPieChart();
pieChart->setData(data); // data为QVector<QPair<QString, double>>类型的饼状图数据
pieChart->setColors(colors); // colors为QVector<QColor>类型的颜色数据

4. 将QPieChart对象添加到QCustomPlot中，并设置其位置和大小。

QCPLayoutGrid *subLayout = new QCPLayoutGrid;
customPlot->plotLayout()->addElement(1, 0, subLayout);
subLayout->addElement(0, 0, pieChart);
subLayout->setMargins(QMargins(5, 5, 5, 5));
subLayout->setRowStretchFactor(0, 1);
subLayout->setColumnStretchFactor(0, 1);
pieChart->setMinimumSize(QSize(200, 200));
pieChart->setMaximumSize(QSize(200, 200));
pieChart->moveCenter(QPointF(0.5, 0.5));

5. 最后，调用QCustomPlot对象的replot()函数进行绘制。

customPlot->replot();

完整的代码示例：

QCustomPlot *customPlot = new QCustomPlot(this);
customPlot->setFixedSize(400, 400);
customPlot->plotLayout()->insertRow(0);
customPlot->plotLayout()->addElement(0, 0, new QCPTextElement(customPlot, "Pie Chart", QFont("sans", 12, QFont::Bold)));

QPieChart *pieChart = new QPieChart();
pieChart->setData(data);
pieChart->setColors(colors);

QCPLayoutGrid *subLayout = new QCPLayoutGrid;
customPlot->plotLayout()->addElement(1, 0, subLayout);
subLayout->addElement(0, 0, pieChart);
subLayout->setMargins(QMargins(5, 5, 5, 5));
subLayout->setRowStretchFactor(0, 1);
subLayout->setColumnStretchFactor(0, 1);
pieChart->setMinimumSize(QSize(200, 200));
pieChart->setMaximumSize(QSize(200, 200));
pieChart->moveCenter(QPointF(0.5, 0.5));

customPlot->replot();