qt之QPainter绘制三种圆形的方式

void MainWindow::paintEvent(QPaintEvent *event){
    QMainWindow::paintEvent(event);

    QPainter painter(this);
    QPen pen(Qt::blue,8);
    pen.setCapStyle(Qt::RoundCap);
    pen.setJoinStyle(Qt::RoundJoin);
    painter.setPen(pen);
    painter.setBrush(Qt::NoBrush);// 关键：无填充
    painter.drawEllipse(10,10,100,100);
    painter.drawArc(120,10,100,100,0,360*16);//后面两个参数表示起始角度和终点角度
    QPainterPath path;
    path.moveTo(230+100, 60);//移动到起始位置
    path.arcTo(230, 10, 100, 100, 0, 360);
    path.closeSubpath();  // 闭合路径
    painter.drawPath(path);

}