try this:
Qt Code: 
  1. void drag::mousePressEvent(QMouseEvent *event)
  2. {
  3.  if (event->button() == Qt::LeftButton)
  4.  {
  5.   QMimeData *mimeData = new QMimeData;
  6.   mimeData->setText("myDrageLabel");
  7.   QDrag *drag = new QDrag(this);
  8.   drag->setMimeData(mimeData);
  9.   Qt::DropAction dropAction = drag->start(Qt::CopyAction | Qt::MoveAction);
  10.   if (dropAction == Qt::MoveAction) 
  11.   {
  12.    close();
  13.    update();
  14.   }
  15.  }
  16. }
  17. in your base class, in which you are using drag object (say myWidget)
  18. myWidget::myWidget(QWidget *parent) : 
  19.                                  QWidget(parent)
  20. {
  21.  setAcceptDrops(true);
  22.  ...
  23. }
  24. void myWidget::dragEnterEvent(QDragEnterEvent *event)
  25. {
  26.  if (event->mimeData()->hasText())
  27.  {
  28.   event->acceptProposedAction();
  29.  }
  30.  else
  31.  {
  32.   event->ignore();
  33.  }
  34. }
  35. void myWidget::dropEvent(QDropEvent *event)
  36. {
  37.  if (event->mimeData()->hasText()) 
  38.  {
  39.   //QString plainText = event->mimeData()->text();
  40.   QPoint dropPos  = event->pos();
  41.   QDragObject *drobj;    
  42.   if ( pixmap() )    
  43.    drobj = new QImageDrag( pixmap()->convertToImage(), this );    
  44.   drobj->move(dropPos);
  45.  
  46.   drobj->show();
  47.  
  48.   if (children().contains(event->source())) 
  49.   {
  50.    event->setDropAction(Qt::MoveAction);
  51.    event->accept();
  52.   } 
  53.   else 
  54.   {
  55.    event->acceptProposedAction();
  56.   }
  57.  }
  58.  else 
  59.  {
  60.   event->ignore();
  61.  }
  62. }
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