Qt实现不同Treewidget之间拖拽

拖拽是编程中经常要用到的，我这里主要是实习了Treewidget之间直接拖拽Item，按下Ctrl键的话是copy，不按Ctrl则是Move。以下是实现代码

class TreeItemMimeData:public QMimeData
{
    Q_OBJECT
public:
    TreeItemMimeData():QMimeData()
    {
        m_pDragItem = NULL;
    }

    ~TreeItemMimeData()
    {

    }

    void SetDragData(QString mimeType , QTreeWidgetItem *pItem)
    {
        m_format<<mimeType;
        m_pDragItem = pItem;
    }



    QStringList formats() const
    {
        return m_format;
    }

    const QTreeWidgetItem* DragItemData() const
    {
        return m_pDragItem;
    }


protected:

    QVariant retrieveData(const QString &mimetype, QVariant::Type preferredType) const
    {
        if (mimetype == "ItemMimeData")
        {
            return m_pDragItem;
        }
        else
        {
             return QMimeData::retrieveData(mimetype, preferredType);
        }
    }
private:
    const QTreeWidgetItem   *m_pDragItem;
    QStringList              m_format;
};

class MyTreeWidget:public QTreeWidget
{
    Q_OBJECT
public:
    MyTreeWidget(QWidget *parent = NULL);
    ~MyTreeWidget();

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

    void dragEnterEvent(QDragEnterEvent *event);
    void dragMoveEvent(QDragMoveEvent *event);
    void dropEvent(QDropEvent *event);
    void keyPressEvent(QKeyEvent *event);
    void keyReleaseEvent(QKeyEvent *event);
private:
    QPoint     m_startDragPoint;
    void       performDrag();
    bool       m_CtrlPressed;

};

MyTreeWidget::MyTreeWidget(QWidget *parent /*= NULL*/):QTreeWidget(parent)
{
    m_CtrlPressed = false;
    this->setSelectionMode(QAbstractItemView::ExtendedSelection);
    this->setAcceptDrops(true);
    this->setDragEnabled(true);
    this->setStyleSheet("QTreeWidget::item:selected{ background-color: rgb(150, 0, 0)}");
}

MyTreeWidget::~MyTreeWidget()
{
}

void MyTreeWidget::keyPressEvent(QKeyEvent *event)
{
    if (event->key() == Qt::Key_Control)
    {
        m_CtrlPressed = true;
    }
}

void MyTreeWidget::keyReleaseEvent(QKeyEvent *event)
{
    if (event->key() == Qt::Key_Control)
    {
        m_CtrlPressed = false;
    }
}

void MyTreeWidget::mousePressEvent(QMouseEvent *event)
{
    if (event->button() == Qt::LeftButton)
    {
        m_startDragPoint = event->pos();
    }
    QTreeWidget::mousePressEvent(event);
}

void MyTreeWidget::mouseMoveEvent(QMouseEvent *event)
{
    if (event->buttons() & Qt::LeftButton)
    {
        int dragDistance = (event->pos() - m_startDragPoint).manhattanLength();
        if (dragDistance > QApplication::startDragDistance())
        {
            performDrag();
        }
    }
    QTreeWidget::mouseMoveEvent(event);

}

void MyTreeWidget::mouseReleaseEvent(QMouseEvent *event)
{
    QTreeWidget::mouseReleaseEvent(event);
}

void MyTreeWidget::dragEnterEvent(QDragEnterEvent *event)
{
    QWidget *source =  qobject_cast<MyTreeWidget *>(event->source());
    if (source /*&& source != this*/)
    {
        if (m_CtrlPressed)
        {
            event->setDropAction(Qt::CopyAction);
        }
        else
        {
            event->setDropAction(Qt::MoveAction);
        }
        /*event->setDropAction(Qt::MoveAction);  */
        event->accept();
    }
}

void MyTreeWidget::dragMoveEvent(QDragMoveEvent *event)
{

    QWidget *source =  qobject_cast<MyTreeWidget *>(event->source());
    if (source /*&& source != this*/)
    {
        const TreeItemMimeData *pMimeData = (const TreeItemMimeData *)(event->mimeData());
        const QTreeWidgetItem *item = pMimeData->DragItemData();
        QTreeWidgetItem *currentItem = this->itemAt(event->pos());
        if (currentItem == item)           //不允许拖回到原来的item
        {
            event->ignore();
        }
        else
        {
            setCurrentItem(currentItem);
            if (m_CtrlPressed)
            {
                event->setDropAction(Qt::CopyAction);
            }
            else
            {
                event->setDropAction(Qt::MoveAction);
            }
            //event->setDropAction(Qt::MoveAction);
            event->accept();
        }

    }
}

void MyTreeWidget::dropEvent(QDropEvent *event)
{
    QWidget *source =  qobject_cast<MyTreeWidget *>(event->source());
    const TreeItemMimeData *pMimeData = (const TreeItemMimeData *)(event->mimeData());
    if (source /*&& source != this*/)
    {
        const QTreeWidgetItem *item = pMimeData->DragItemData();
        QTreeWidgetItem *pItem = item->clone();
        QTreeWidgetItem *currentItem = this->itemAt(event->pos());

        if (currentItem && (currentItem != item))
        {
            currentItem->addChild(pItem);
        }
        else
        {
            this->addTopLevelItem(pItem);
        }
        if (m_CtrlPressed)
        {
            event->setDropAction(Qt::CopyAction);
        }
        else
        {
            event->setDropAction(Qt::MoveAction);
        }
        //event->setDropAction(Qt::MoveAction);
        event->accept();
    }
}

void MyTreeWidget::performDrag()
{
    QTreeWidgetItem *item = currentItem();
    if (item)
    {

        TreeItemMimeData *mimeData = new TreeItemMimeData;
        mimeData->SetDragData("ItemMimeData",item);

        QDrag *drag = new QDrag(this);
        drag->setMimeData(mimeData);
        drag->setPixmap(QPixmap(":/DragDropDemo/Resources/Mail.png"));
        if (m_CtrlPressed)
        {
            drag->exec(Qt::CopyAction);
        }
        else
        {
            drag->exec(Qt::MoveAction);
            delete item;
        }

    }
}

以下是我演示的截图

http://blog.csdn.net/hai200501019/article/details/9322329