Changing row order by dragging them

[shadowfax]

I want to change row order in my custom model by dragging them. I've table view and custom model using QAbstractTableModel. I need the same behaviour as in listWidget , when I can reorder items by dragging them. What I need to do to achieve the same effect in model/view ?

[wysota]

You need to teach your model to do that by implementing QAbstractItemModel::mimeData() and QAbstractItemModel::dropMimeData().

[shadowfax]

I'm having problem with mimeData and dropMimeData implementation. If I implement both of them only mimeData method is working. When I implement only one of them they're correctly invoked. What should I do to have both methods working correctly ?

[wysota]

How did you reimplement them?

[shadowfax]

I reimplemented them in the most basic form in order to check if they're working:

def dropMimeData(self, data, action, row, column, parentIndex):
    print 'drop'
    return True
 
def mimeData(self, indexes):
    print 'drag'
    mime = QtCore.QMimeData()
    return mime

def dropMimeData(self, data, action, row, column, parentIndex):
    print 'drop'
    return True

def mimeData(self, indexes):
    print 'drag'
    mime = QtCore.QMimeData()
    return mime

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[wysota]

Essentially your mimeData implementations says "I do not accept any drops" so dropMimeData will never be called.

[shadowfax]

How should I enable drop in mimeData method ? According to Qt reference mimeData contains data corresponding to indexes, so what I need to do to enable drop in this method ? I was thinking that mimeData method only returns mimeData object based on indexes. If there is any example that shows how to do this ?

[wysota]

Did you reimplement mimeTypes() as well? I confused the two methods a bit. Your mimeData() actually says "I don't have anything interesting to drag" and not "I don't accept drops". That's what mimeTypes() returns. Read the docs for all three methods, you'll need them all.