Qt实现不同Treewidget之间拖拽

class TreeItemMimeData:public QMimeData{Q_OBJECTpublic: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_OBJECTpublic: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;}}}