利用QPainter作图

void MyPainter::paintEvent(QPaintEvent */*event*/)
{
    QPainter painter(this);
    //设定钢笔工具
    QPen pen;
    pen.setStyle(Qt::SolidLine);
    pen.setWidth(1);
    pen.setBrush(Qt::blue);
    pen.setCapStyle(Qt::RoundCap);
    pen.setJoinStyle(Qt::RoundJoin);
    painter.setPen(pen);
    //设定线性渐变工具，可加入到刷子工具中使用
    QLinearGradient gradient(10,10,100,100);
    gradient.setColorAt(0.0,Qt::white);
    gradient.setColorAt(0.2,Qt::red);
    gradient.setColorAt(0.8,Qt::black);
    //设定刷子工具
    QBrush brush(gradient);
    //brush.setColor(Qt::red);
    //brush.setStyle(Qt::SolidPattern);
    painter.setBrush(brush);
    //作路径
    QPainterPath path;
    path.moveTo(20,20);
    path.cubicTo(20,45,56,39,56,45);
    //设定反锯齿作图，可使得曲线平滑
    painter.setRenderHint(QPainter::Antialiasing,true);    
    //画图
    painter.save();//保存状态
    //painter.drawLine(10,10,200,200);
    painter.drawRect(10,10,50,50);
    //painter
    //painter.drawPath(path);
    painter.restore();//恢复状态
}