Qt QPainter类 画板的使用

//头文件

void paintEvent(QPaintEvent *paintEven);

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//Set Paint Testvoid mouseWidget::paintEvent(QPaintEvent *paintEven){QPainter  painter(this);painter.setPen(QPen(QColor(255,0,0)));painter.setBrush(QBrush(QColor(0,255,0,255),Qt::BrushStyle::Dense3Pattern));painter.drawRect(0,50,200,50);//set gradient QLinearGradient gradientLine(0,100,200,150);gradientLine.setColorAt(0,Qt::red);gradientLine.setColorAt(0.2,Qt::black);gradientLine.setColorAt(0.4,Qt::yellow);gradientLine.setColorAt(0.6,Qt::white);gradientLine.setColorAt(0.8,Qt::green);gradientLine.setColorAt(1,Qt::blue);painter.setBrush(gradientLine);painter.drawRect(0,100,200,50);        //set cycle gradient        //set cycle gradient    QRadialGradient radialGradient(300,100,100,300,100);//其中参数分别为圆形渐变的圆心（ 200， 100），半径 100，和焦点（ 200， 100）    radialGradient.setColorAt(0,Qt::black);    radialGradient.setColorAt(1,Qt::yellow); //这里让焦点和圆心重合，从而形成从圆心向外渐变的效果    painter.setBrush(radialGradient);    painter.drawEllipse(200,0,200,200);}