1、设置当前界面背景颜色

设置软件当前界面背景颜色

    QColor color(0, 11, 38);
    painter.setBrush(color);
    //painter.drawRect(this->rect());
    painter.drawRect(0,0,this->width(),this->height());

2、设置渐变填充矩形

   //线性渐变 示例
    QLinearGradient linearGradient(QPointF(40, 190), QPointF(70, 190));
    //插入颜色
    linearGradient.setColorAt(0, Qt::yellow);
    linearGradient.setColorAt(0.5, Qt::red);
    linearGradient.setColorAt(1, Qt::green);
    //指定渐变区域以外的区域的扩散方式
    linearGradient.setSpread(QGradient::RepeatSpread);
    //使用渐变作为画刷
    painter.setBrush(linearGradient);
    painter.drawRect(10, 20, 90, 40);//矩形渐变填充

3、效果