Qt画笔实现折线图

参考：https://www.cnblogs.com/lsgxeva/p/7821550.html
效果图：

void BrokenLine::paintEvent(QPaintEvent *event)

{

    // 折线上的点

    static QList<QPointF> points = QList<QPointF>() << QPointF(10, 40) << QPointF(100, 100) << QPointF(200, 100)

                                                    << QPointF(300, 100) << QPointF(330, 80) << QPointF(350, 70);

    QPainter painter(this);

    painter.setRenderHint(QPainter::Antialiasing, true);

    painter.setPen(QPen(Qt::black, 2));

    QPainterPath path(points[0]);

    for (int i = 1; i < points.size(); ++i)

    {

        path.lineTo(points[i]);

    }

    // 绘制 path

    painter.drawPath(path);

    // 绘制折线上的标记点

    painter.setBrush(Qt::gray);

    int ellipse_size = 4;

    for (int i = 0; i < points.size(); ++i) {

        painter.drawEllipse(points[i], ellipse_size, ellipse_size);

        QString text = QString::number(points[i].y());

        QFontMetrics fm = painter.fontMetrics();

        int height_font = fm.height();

        int width_text = fm.width(text);

        QPointF textPos(points[i].x()-(width_text/2), points[i].y()-(ellipse_size/2)-(height_font/2));

        painter.drawText(textPos, text);

    }

    return QWidget::paintEvent(event);

}