Qt 控件添加阴影效果

在做项目的时候，为了美化界面，我们通常需要设置控件具有阴影效果，具体怎么做呢？ 

方法一：使用QGraphicsDropShadowEffect

    QGraphicsDropShadowEffect *shadow_effect = new QGraphicsDropShadowEffect(this);
    shadow_effect->setOffset(5, 5);              //阴影的偏移量
    shadow_effect->setColor(QColor(43, 43, 43)); //阴影的颜色
    shadow_effect->setBlurRadius(8);             // 阴影圆角的大小
    
    QLabel* pLabel = new QLabel(this);
    pLabel->setGraphicsEffect(shadow_effect); //给那个控件设置阴影，这里需要注意的是所有此控件的子控件，也都继承这个阴影。

阴影效果如图：

方法二:重写paintEvent 函数 

void MainWindow::paintEvent(QPaintEvent *event)
{
    QPainterPath path;
    path.setFillRule(Qt::WindingFill);
    path.addRect(10, 10, this->width()-20, this->height()-20);
 
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing, true);
    painter.fillPath(path, QBrush(Qt::white));
 
    QColor color(0, 0, 0, 50);
    for(int i = 0; i < 10; i++)
    {
        QPainterPath path;
        path.setFillRule(Qt::WindingFill);
        path.addRect(10-i, 10-i, this->width()-(10-i)*2, this->height()-(10-i)*2);
        color.setAlpha(150 - qSqrt(i)*50);
        painter.setPen(color);
        painter.drawPath(path);
    }
}
 
 
bool TDMSummaryForm::eventFilter(QObject *watched, QEvent *event)
{
    if (event->type() == QEvent::Paint && (watched == ui->titleFrame ||
                                           watched == ui->groupDataFrame ||
                                           watched == ui->trendFrame ||
                                           watched == ui->tableFrame))
    {
        QWidget *wgt = static_cast<QWidget*> (watched);
 
        QPainter painter(wgt);
        QColor color(217, 229, 246, 55);
        for (int i = 0; i<10; i++)
        {
            QPainterPath path;
            path.setFillRule(Qt::WindingFill);
            path.addRoundRect(10 - i, 10 - i,
                              wgt->width() - (10 - i) * 2,
                              wgt->height() - (10 - i) * 2,
                              4);
            color.setAlpha(255 - qSqrt(i) * 70);
            painter.setPen(color);
            painter.drawPath(path);
        }
    }
 
    return QObject::eventFilter(watched, event);
}

使用此方法，需要添加下面代码，保证不被绘制上的部分透明。

setAttribute(Qt::WA_TranslucentBackground)

方法三：使用带有阴影效果的图片。