C/C++ QChart如何自定义显示柱状图每根柱子的数值，请给出详细代码

在QCharts中，要自定义显示柱状图（Bar Chart）的每根柱子的数值，你可以通过创建一个`QChartItemDelegate`来实现。这个委托会在绘制每个条形时处理额外的内容，如文本标签。以下是一个简单的例子：

#include <QApplication>
#include <QChart>
#include <QChartView>
#include <QColumnDataSource>
#include <QDate>
#include <QDateTime>
#include <QFontMetricsF>
#include <QPen>
#include <QTextItem>
#include <QValueAxis>

class CustomBarDelegate : public QAbstractItemDelegate
{
public:
    CustomBarDelegate(QObject *parent = nullptr)
        : QAbstractItemDelegate(parent) {}

protected:
    void paint(QPainter *painter,
               const QStyleOptionViewItem &option,
               const QModelIndex &index) const override {
        QChartItem *item = static_cast<QChartItem *>(index.internalPointer());
        if (item->type() == QChart::BarSeries) {
            auto bar = qobject_cast<const QBarSeries *>(item)->bar(index.row());

            // 绘制柱子
            painter->save();
            painter->setRenderHint(QPainter::Antialiasing);
            item->draw(painter, option);

            // 获取字体大小和坐标
            QFontMetricsF metrics(option.font);
            QRectF textRect = painter->viewport()->rect().translated(option.rect.topLeft());
            textRect.setWidth(bar.width());
            textRect.setHeight(metrics.height() + 5); // 可调整文字上下间距

            // 文本内容
            QString text = qvalueToKey(bar.value()); // 假设qvalueToKey函数将值转换成字符串
            QTextItem *textItem = new QTextItem(text, painter, textRect);

            // 设置颜色和对齐
            textItem->setFont(option.font);
            textItem->setPen(Qt::black);
            textItem->setAlignment(Qt::AlignCenter);

            painter->restore();
        }
        QAbstractItemDelegate::paint(painter, option, index);
    }

private:
    QPen m_pen;
};

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

    // 创建数据源
    QDate startDate(2023, 1, 1);
    QDate endDate(2023, 12, 31);
    QVector<int> data = {10, 20, 30, 40, 50, 60, 70, 80, 90, 100}; // 柱状图的数据
    QVector<QDateTime> dates = QDateTime::from日期(startDate.addDays(i), Qt::UTC).toLocalTime()
                                 for (int i = 0; i < data.size(); ++i);

    QColumnDataSource dataSource(dates, 0, data, 0, "Date", "Value");

    // 创建图表
    QChart chart("Custom Bar Chart");
    chart.setAnimationOptions(QChart::NoAnimation);
    chart.setTitle(QStringLiteral("Custom Bar Chart with Values"));

    // 添加轴
    QValueAxis *axisX = new QValueAxis();
    axisX->setTitle(QStringLiteral("Date"));
    chart.addAxis(axisX, Qt::AlignBottom);
    chart.createDefaultAxes();

    // 添加系列
    QBarSeries *series = new QBarSeries();
    series->append(dates, data);
    chart.addSeries(series);

    // 自定义代理
    CustomBarDelegate delegate;
    chart.setItemDelegate(&delegate);

    // 视图
    QChartView view(&chart);
    view.setRenderHint(QPainter::Antialiasing);

    // 显示图表
    QWidget window;
    QVBoxLayout *layout = new QVBoxLayout(&window);
    layout->addWidget(&view);
    window.show();

    return app.exec();
}

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