Qt After drop event - qt

Question

I need to process some data AFTER a drop event has occured on a widget.
i.e a user selects some items in list A and drops them in list B. My program needs to compare the 2 lists after B has added the items selected from A.
Any ideas?

Answer 1

Here's a PyQt script that demonstrates two ways to trap drop events:
from PyQt4 import QtGui, QtCore
class Window(QtGui.QMainWindow):
def __init__(self):
QtGui.QMainWindow.__init__(self)
widget = QtGui.QWidget(self)
self.setCentralWidget(widget)
layout = QtGui.QVBoxLayout(widget)
self.listA = ListWidget(self)
self.listB = QtGui.QListWidget(self)
self.listB.viewport().installEventFilter(self)
for widget in (self.listA, self.listB):
widget.setAcceptDrops(True)
widget.setDragEnabled(True)
for item in 'One Two Three Four Five Six'.split():
widget.addItem(item)
layout.addWidget(widget)
def eventFilter(self, source, event):
if (event.type() == QtCore.QEvent.Drop and
source is self.listB.viewport()):
self.listB.dropEvent(event)
if event.isAccepted():
print 'eventFilter', self.listB.count()
return True
return QtGui.QMainWindow.eventFilter(self, source, event)
class ListWidget(QtGui.QListWidget):
def __init__(self, parent):
QtGui.QListWidget.__init__(self, parent)
def dropEvent(self, event):
QtGui.QListWidget.dropEvent(self, event)
if event.isAccepted():
print 'dropEvent', self.count()
if __name__ == '__main__':
import sys
app = QtGui.QApplication(sys.argv)
window = Window()
window.show()
sys.exit(app.exec_())

Answer 2

The event you're listening for is QDropEvent. To do some work on receipt of the event you'll need to either:
Reimplement QWidget::dropEvent on the target widget or
Use a separate controller widget as an event filter for the drop target (reimplement QObject::eventFilter on the controller and then install it on the target [installEventFilter]).
EDIT: Going into more depth:
Reimplementing dropEvent
Header:
cDropTarget : public QWidget
{
Q_OBJECT
public:
cDropTarget(QWidget *Parent = 0);
protected:
virtual void dropEvent(QDropEvent *event);
}
Implementation:
cDropTarget::cDropTarget(QWidget *Parent)
: QWidget(Parent)
{
setAcceptDrops(true);
}
void cDropTarget::dropEvent(QDropEvent *event)
{
//check that you want to process the drop event
//i.e. its mimeData()->hasFormat(that you can interpret)
//extract mimeData() from the drop event
//do something with it
}
Using a separate event filter
header:
cDropEventFilter : public QObject
{
...
protected:
virtual bool eventFilter(QObject *watched, QEvent *event);
...
}
Implementation:
bool cDropEventFilter::eventFilter(QObject *watched, QEvent *event)
{
if(event->type() == QEvent::DropEnter)
{
QDropEvent *DropEvent = static_cast<QDropEvent*>(event);
if (DropEvent->mimeData()->hasFormat(MIME_TYPE))
{
DropEvent->acceptProposedAction();
return true;
}
}
else
{
return QObject::eventFilter(watched, event);
}
//Handle all events not matching mimeData format MIME_TYPE
event->ignore();
return true;
}

Answer 3

Got it working!
My code for anyone interested:
class MyList(QListWidget):
def __init__(self , parent = None):
super(MyList, self).__init__(parent)
self.setAlternatingRowColors(True)
self.setDragDropMode( QAbstractItemView.InternalMove )
def dropEvent( self , event ):
# get index to insert at
insertPos = event.pos()
fromList = event.source()
insertRow = fromList.row( fromList.itemAt( insertPos ) )
lowestRow = insertRow
for item in fromList.selectedItems():
name = item.text()
sip.delete( item )
listItem = QListWidgetItem( name )
listItem.setTextAlignment( Qt.AlignHCenter )
self.insertItem( insertRow , listItem )
insertRow += 1
self.emit( SIGNAL("stuffDropped") , lowestRow )
event.accept()