stackUnder是什么意思？根据官方的解析，简而言之一句话：把窗口的小部件放置于父窗口的堆栈窗口中。本文将通过一则简单的示例，来具体解析stackUnder该如何使用。

官方解析

void QWidget::stackUnder(QWidget *w)
Places the widget under w in the parent widget's stack.
To make this work, the widget itself and w must be siblings.
See also raise() and lower().

示例代码

#include "widget.h"
#include "ui_widget.h"
#include <QMouseEvent>

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);

    for (int i=0; i<10; i++)
    {
        QLabel *label = new QLabel(this);
        label->setText("label_" + QString::number(i));
        //
        QRect rc = QRect(30+i*30, 30+i*20, 150, 80);
        label->setGeometry(rc);
        //
        QString qss = QString("background-color:rgb(100,%1,200); "
                              "border-radius:10px; "
                              "color:rgb(250,%2,250);").arg(i*10).arg(200+i*2);
        label->setStyleSheet(qss);
        //
        label->stackUnder(this);
        label->raise();

        m_labels << label;
        m_rects << rc;
    }

}

Widget::~Widget()
{
    delete ui;
}

void Widget::mouseReleaseEvent(QMouseEvent *event)
{
    if(event->button() == Qt::LeftButton){
        QPoint pt = event->pos();
        int index = 0;
        for (int i=0; i<m_rects.size(); i++) {
            QRect rc = m_rects.at(i);
            if(rc.contains(pt.x(), pt.y())){
                index = i;
            }
        }
        m_labels.at(index)->raise();

        this->update();
        event->accept();
    }
}

运行效果