QTreeWidget实现元素拖拽移动，并绘制插入点

#include "ctreewidget.h"
#include 
#include 

#define BM_ICON_WIDTH 22

CTreeWidget::CTreeWidget(QWidget *parent) :
    QTreeWidget(parent),m_child(true),m_newLine(QLine()), m_oldLine(QLine())
{
    this->setSelectionMode(QAbstractItemView::SingleSelection);
    //启用拖放
    this->setDragEnabled(true);
    //设置拖放
    setAcceptDrops(true);
//    this->viewport()->setAcceptDrops(true);
    //设置显示将要被放置的位置
    this->setDropIndicatorShown(true);
//    //设置拖放模式为移动项目，否则为复制项目
    this->setDragDropMode(QAbstractItemView::InternalMove);
    this->setAttribute(Qt::WA_PaintOutsidePaintEvent);
}

void CTreeWidget::dragEnterEvent(QDragEnterEvent *event)
{
    if (event->mimeData()->hasFormat("application/x-qabstractitemmodeldatalist"))
        event->accept();
    else
        event->ignore();
}

void CTreeWidget::dragMoveEvent(QDragMoveEvent *event)
{
    if (event->mimeData()->hasFormat("application/x-qabstractitemmodeldatalist")) {
        QTreeWidgetItem *hHitTest = itemAt(event->pos());
        event->setDropAction(Qt::MoveAction);
        if(hHitTest)
        {
            QPoint pos = event->pos();
            QRect rect = visualItemRect(hHitTest);
            m_oldLine = m_newLine;
            m_newLine = QLine(rect.bottomLeft(), rect.bottomRight());
            int left = rect.left() + BM_ICON_WIDTH + 3;
            if(pos.x() > left )
            {
                m_newLine.setP1(QPoint(left, m_newLine.y1()));
                m_child = true;
            }
            else
                m_child = false;

            QByteArray itemData = event->mimeData()->data("application/x-qabstractitemmodeldatalist");
            QTreeWidgetItem *dragItem = (QTreeWidgetItem*)((void*)QVariant(itemData).toInt());

            //绘线
            paintInsertPos(dragItem, hHitTest);
        }
        event->accept();
    } else
        event->ignore();
}

void CTreeWidget::dropEvent(QDropEvent *event)
{
    if (event->mimeData()->hasFormat("application/x-qabstractitemmodeldatalist"))
    {
        QByteArray itemData = event->mimeData()->data("application/x-qabstractitemmodeldatalist");
        QTreeWidgetItem *item = (QTreeWidgetItem*)((void*)QVariant(itemData).toInt());
        QTreeWidgetItem *pItem = itemAt(event->pos());
        if(pItem == item || pItem == NULL)
        {
            event->ignore();
            return;
        }

        //移除
        if(item->parent())
        {
            item->parent()->removeChild(item);
        }
        else
        {
            takeTopLevelItem(indexOfTopLevelItem(item));
        }
        //插入
        if(pItem &&m_child)
        {
            pItem->insertChild(0, item);
        }
        else if(pItem)
        {
            QTreeWidgetItem *parentItem = pItem->parent();
            if(parentItem)
                parentItem->insertChild(parentItem->indexOfChild(pItem)+1, item);
            else
                insertTopLevelItem(indexOfTopLevelItem(pItem)+1, item);
        }
        ////////////////////////////////////////////

        event->setDropAction(Qt::MoveAction);
        event->accept();
    } else
        event->ignore();
    QTreeWidget::dropEvent(event);
}

void CTreeWidget::startDrag(Qt::DropActions supportedActions)
{
    Q_UNUSED(supportedActions);
    QTreeWidgetItem *item = currentItem();
    if(item == NULL)
        return;

    QString pValue = QString::number(int((void*)item));
    QByteArray itemData;
    itemData = QVariant(pValue).toByteArray();

    QMimeData *mimeData = new QMimeData;
    mimeData->setData("application/x-qabstractitemmodeldatalist", itemData);

    QDrag *drag = new QDrag(this);
    drag->setMimeData(mimeData);

    //设置鼠标移动时，拖动的图片数据
    //QPixmap pPixmap(":/Drag.png");
    //pPixmap = pPixmap.scaledToWidth(2);
    //drag->setPixmap(pPixmap);
    //drag->setHotSpot(QPoint(drag->pixmap().width()/2, drag->pixmap().height()/2));

    if (drag->exec(Qt::MoveAction) == Qt::MoveAction)
    {
    }
}

void CTreeWidget::paintInsertPos(QTreeWidgetItem *dragItem, QTreeWidgetItem *hitItem)
{
    QPainter painter(this);
    painter.save();
    /***********擦除旧线***********/
    //直线
    QPen pen(palette().base().color());
    painter.setPen(pen);
    painter.drawLine(m_oldLine);
    //三角
    paintTriangle(m_oldLine.p1(), &painter);

    //在原item则不绘制线
    if(dragItem == hitItem)
    {
        m_newLine = QLine();
        return;
    }
    /***********绘制新线***********/
    //直线
    pen.setColor(Qt::green);
    pen.setWidth(1);
    painter.setPen(pen);
    painter.drawLine(m_newLine);
    painter.restore();
    //三角
    paintTriangle(m_newLine.p1(), &painter);
}

void CTreeWidget::paintTriangle(const QPoint &right, QPainter *painter)
{
    QPoint top = QPoint(right.x()-4, right.y()-3);
    QPoint bottom = QPoint(right.x()-4, right.y()+3);
    painter->drawLine(right, top);
    painter->drawLine(top, bottom);
    painter->drawLine(bottom, right);
}