QTabWidget 实现类似QQ聊天窗口（拖动分离出新的窗口）

        新版本的QQ聊天窗口可以实现拖动，分离出新的窗口。浏览器等软件也可以实现类似操作。所以心血来潮想用Qt实现类似的功能。想用QTabWidget直接实现是很难的，仔细阅读源码，发现QTabWidget内部是由QStackedWidget和QTabBar组合实现的。所以很自然的想到，只要继承QTabBar的子类重新实现QTabBar的

void mousePressEvent (QMouseEvent *e);
void mouseMoveEvent (QMouseEvent *e);
void mouseReleaseEvent (QMouseEvent *e);

这三个方法，再把子定义的TabBar设置给QTabWidget就差不多了。但是还有个问题，QTabWidget的 setTabBar方法是protected的，所以只好再自定义一个QTabWidget的子类，在子类里调用setTabBar了。以下是我的简单实现：

class myTabBar:public QTabBar
{
    Q_OBJECT
public:
    myTabBar(QWidget *parent = NULL);
    ~myTabBar();
protected:
    void mousePressEvent (QMouseEvent *e);
    void mouseMoveEvent (QMouseEvent *e);
    void mouseReleaseEvent (QMouseEvent *e);

 signals:
    void starDragTab(int index);
    void endDragTab();
private:
    void drag();

    bool      m_isDrag;
    QPoint    m_mousePressPoint;
    QPoint    m_mouseReleasePoint;

};

void myTabBar::mouseMoveEvent(QMouseEvent *e)
{
    int index = this->currentIndex();

    if (m_isDrag)
    {
        QPoint Point = e->pos();

                //拖动的垂直距离大于Bar的高度的话就新建一个窗口，这个应该比较好理解啊
        if (qAbs(m_mousePressPoint.y() - Point.y()) > this->height())
        {
            emit starDragTab(index);
        }
    }
    QTabBar::mouseMoveEvent(e);
}

void myTabBar::mousePressEvent(QMouseEvent *e)
{
    if (e->button() == Qt::LeftButton)
    {
        m_isDrag = true;
        m_mousePressPoint = e->pos();
    }
    QTabBar::mousePressEvent(e);
}

void myTabBar::mouseReleaseEvent(QMouseEvent *e)
{
    if (e->button() == Qt::LeftButton)
    {
        m_mouseReleasePoint = e->pos();
        if (qAbs(m_mousePressPoint.y() - m_mouseReleasePoint.y()) > this->height())
        {
            emit endDragTab();
        }
    }
    QTabBar::mouseReleaseEvent(e);
}

class myTabWidget:public QTabWidget
{
    Q_OBJECT

public:
    myTabWidget(QWidget *parent = NULL);

    ~myTabWidget();


private slots:
    void starDrag(int index);
    void endDrag();

private:
    myTabBar      *m_pTabBar;
    QString        m_dragTabLabel;
    QWidget       *m_pDragWidget;
    int            m_dragIndex;


};

myTabWidget::myTabWidget(QWidget *parent/* = NULL*/):QTabWidget(parent)
{
    this->setAcceptDrops(true);
    setMouseTracking(true);
    m_pTabBar = new myTabBar(this);
    m_pTabBar->setMovable(true);
    setTabBar(m_pTabBar);               //设置自定义的Bar给TabWidget
    m_pDragWidget = NULL;
    connect(m_pTabBar,SIGNAL(starDragTab(int)),this,SLOT(starDrag(int)));
    connect(m_pTabBar,SIGNAL(endDragTab()),this,SLOT(endDrag()));
}

void myTabWidget::starDrag(int index)
{
    m_dragTabLabel = this->tabText(index);
    m_pDragWidget  = this->widget(index);
    m_dragIndex    = index;
    QPixmap pix;
    //pix = QPixmap::grabWidget(m_pDragWidget);
    pix = QPixmap::grabWindow(this->winId());
    if (pix.isNull())
    {
        int i;
    }
    QMimeData *mimeData = new QMimeData;
    //mimeData->setText("drag tab");
    QDrag *drag = new QDrag(this);
    drag->setMimeData(mimeData);
    drag->setPixmap(pix.scaled(QSize(200,200)));    //这里主要是想想QQ一样，可以拖动的过程显示被拖动窗口的图片。但是效果还不是很好
    drag->exec();
}

void myTabWidget::endDrag()
{
    myTabWidget *pWidget = new myTabWidget(NULL);
    if (m_pDragWidget)
    {

                //新建一个独立的窗口
    removeTab(m_dragIndex);
    pWidget->addTab(m_pDragWidget,m_dragTabLabel);
    pWidget->show();
}

http://blog.csdn.net/hai200501019/article/details/8987379