2019独角兽企业重金招聘Python工程师标准>>> 
#include <QPainter>
void MyView::paintEvent(QPaintEvent * event)
{
qDebug("************MyView::paintEvent*****************");
// QPainter painter; //QWidget::paintEngine: Should no longer be called
QPainter painter(this->viewport()); //关键这一句
QLinearGradient ling(QPointF(70, 70), QPoint( 140, 140 ) ); //从起点到终点的渐变
ling.setColorAt(0, Qt::blue); //起点到中心要显示的颜色
ling.setColorAt(1, Qt::green);
ling.setSpread( QGradient::PadSpread ); //默认显示模式
QBrush brush(ling);
painter.setBrush(brush);
painter.drawRect(0, 0, 200, 200);
painter.end();
QGraphicsView::paintEvent(event);
}