#ifndef BFWIDGET_H
#define BFWIDGET_H

#include <QWidget>
#include <QMouseEvent>
#include <QResizeEvent>

/**
 * 窗口可以拖动
 * 窗口增加阴影效果
 * @brief The BFWidget class
 */
class BFWidget : public QWidget
{
    Q_OBJECT
public:
    explicit BFWidget(QWidget *parent = 0);

    /**
     * 重写空间排版设置
     * 把空间排版到central_widget上面
     * @brief setLayout
     * @param layout
     */
    void setLayout(QLayout * layout);

signals:

public slots:

protected:
    void mousePressEvent(QMouseEvent *event);
    void mouseReleaseEvent(QMouseEvent *event);
    void mouseMoveEvent(QMouseEvent *event);
    //void resizeEvent(QResizeEvent *event);

private:
    //显示内容的区域
    QWidget     *central_widget;

    QPoint move_point; //移动的距离
    bool mouse_press; //按下鼠标左键

};

#endif // BFWIDGET_H

<pre name="code" class="cpp">#include <QBoxLayout>
#include <QPalette>
#include <QGraphicsDropShadowEffect>
#include <QDebug>
#include <QSizePolicy>

#include "bfwidget.h"

BFWidget::BFWidget(QWidget *parent) :
    QWidget(parent)
{
    setWindowFlags(Qt::FramelessWindowHint);
    setAttribute(Qt::WA_TranslucentBackground);

    central_widget = new QWidget();
    central_widget->setSizePolicy(QSizePolicy::Expanding,QSizePolicy::Expanding); ////水平方向和垂直方向任意伸展

    QPalette palette;
    palette.setBrush(QPalette::Background,QBrush(QColor(255,255,255)));
    central_widget->setPalette(palette);
    central_widget->setAutoFillBackground(true);

    QGraphicsDropShadowEffect *shadow_effect = new QGraphicsDropShadowEffect();
    shadow_effect->setBlurRadius(10.0);
    shadow_effect->setColor(QColor(0, 0, 0, 100));
    shadow_effect->setOffset(1.0);
    central_widget->setGraphicsEffect(shadow_effect);

    QVBoxLayout * main_layout = new QVBoxLayout();
    main_layout->addWidget(central_widget, Qt::AlignCenter);
    main_layout->addSpacing(0);
    main_layout->setContentsMargins(5,5,5,5);
    QWidget::setLayout(main_layout);
}

void BFWidget::setLayout(QLayout *layout)
{
    central_widget->setLayout(layout);
}

void BFWidget::mousePressEvent( QMouseEvent * event )
{
    //只能是鼠标左键移动和改变大小
    if(event->button() == Qt::LeftButton)
    {
        mouse_press = true;
    }

    //窗口移动距离
    move_point = event->globalPos() - pos();
}

void BFWidget::mouseReleaseEvent(QMouseEvent *)
{
    mouse_press = false;
}

void BFWidget::mouseMoveEvent(QMouseEvent *event)
{
    //移动窗口
    if(mouse_press)
    {
        QPoint move_pos = event->globalPos();
        move(move_pos - move_point);
    }
}

//void BFWidget::resizeEvent(QResizeEvent *event)
//{
//    QSize size = event->size();
//    central_widget->setGeometry(5, 5, size.width() - 10, size.height() - 10);
//    qDebug() << central_widget->rect();
//}

qt实现类似qq的阴影窗体