qt4怎么用不同颜色 绘制路径

    QPainterPath path;    path.moveTo(50,50);    path.lineTo(100,100);    path.lineTo(150,50);    path.lineTo(200,100);    QPainter painter(this);    QPen pen,pen1;    pen.setColor(QColor(255,0,0));//红色    painter.setPen(pen);    painter.drawPath(path);    //下面的代码不加的话,画出来的线就是红色的    pen.setColor(QColor(255,0,255));//紫色    path.moveTo(100,50);    path.lineTo(200,200);    path.lineTo(300,50);    painter.setPen(pen);    painter.drawPath(path);//结果画来的的线都是紫色的,为什么呢?