同一个类下对函数有不同的实现方法,称为重载
重载:函数名称不变,入口参数(数量和类型)可以改变,出口参数(返回值)可以改变
QPen pen(Qt::green,3,Qt::DashDotLine,Qt::RoundCap,Qt::RoundJoin);
//画笔参数:画笔颜色,线宽,画笔形状
painter.drawLine(0,0,100,100);//画直线
c
//画线
QPainter painter(this);
painter.drawLine(QPoint(0,0),QPoint(100,100));//从(0,0)点画到(100,100)
painter.drawLine(QPoint(100,100),QPoint(0,200));
painter.drawLine(0,200,200,200);
painter.drawLine(200,200,100,100);