1.思路：标签QLabel 改变形状，根据情况显示背景色

2.代码实现

setLED(QLabel *label, int color, int size)
{
    label->setText("");
    QString min_width = QString("min-width: %1px;").arg(size);
    QString min_height = QString("min-height: %1px;").arg(size);
    QString max_width = QString("max-width: %1px;").arg(size);
    QString max_height = QString("max-height: %1px;").arg(size);

    QString border_radius = QString("border-radius: %1px;").arg(size/2);
    QString border = QString("border:1px solid black;");

    QString background = "background-color:";
    switch (color) {
    case 0:
        //灰色
        background += "rgb(190, 190, 190)";
        break;
    case 1:
        //红色
        background += "rgb(255, 0, 0)";
        break;
    case 2:
        //绿色
        background += "rgb(0, 255, 0)";
        break;
    default:
        break;
    }
    const QString Sheetstyle1 = min_width+min_height+max_width+max_height +border_radius+border+background;
    label->setStyleSheet(Sheetstyle1);
}

3.结果显示

QT代码实现圆形指示灯_LED