使用QPainter进行简单的画图

void Widget::paintEvent(QPaintEvent *){//重写paintEvent()事件
    int i = 0;
    QPainter painter(this);
    QPen pen(QColor(0,0,255),2,Qt::SolidLine,Qt::RoundCap,Qt::RoundJoin);
    painter.setPen(pen);
    painter.setRenderHint(QPainter::Antialiasing, true);//抗锯齿
    int startAngle = 20*16;//起始角度
    int spanAngle = 320*16;//跨度
    while(i<100){
        i = i+1;
        QRectF rectangle(i,i,200-2*i,200-2*i);//画弧，注意后两个参数也是相对坐标
        painter.drawArc(rectangle,startAngle,spanAngle);
    }
}