Drag and Drop Data among multiple QTreeWidget

Question

I have a number of QTreeWidget. Here, there are two trees. the left one has "a" , "b". I want to drag this item into the right tree. I have no error but the item become empty. How should I do for dragging the left data to the right tree? and why?

data is this.

b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\n\x00\x00\x00\x00\x02\x00a\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\n\x00\x00\x00\x00\x02\x00b'

---

from PySide import QtCore
from PySide import QtGui

import sys

class MainWindow(QtGui.QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent=None)

        self.sequoia = Sequoia()
        self.baobab = Baobab()
        self.c_widget = QtGui.QWidget()
        h_boxlayout = QtGui.QHBoxLayout()
        h_boxlayout.addWidget(self.sequoia, 30)
        h_boxlayout.addWidget(self.baobab, 70)
        self.c_widget.setLayout(h_boxlayout)
        self.setCentralWidget(self.c_widget)
class Sequoia(QtGui.QTreeWidget):
    def __init__(self, parent=None):
        super(Sequoia, self).__init__(parent=None)
        self.setColumnCount(2)
        self.setAcceptDrops(True)
        self.setDragDropMode(QtGui.QAbstractItemView.InternalMove)
        self.sampleitem = QtGui.QTreeWidgetItem()

        self.sampleitem.setText(0, "a")
        self.sampleitem.setText(1, "b")
        self.addTopLevelItem(self.sampleitem)

class Baobab(QtGui.QTreeWidget):
    def __init__(self, parent=None):
        super(Baobab, self).__init__(parent=None)
        self.setDragDropMode(QtGui.QAbstractItemView.InternalMove)
        self.setColumnCount(2)
    def dragEnterEvent(self, event):
        if event.mimeData().hasFormat('application/x-qabstractitemmodeldatalist'):
            event.accept()
        return QtGui.QTreeWidget.dragEnterEvent(self, event)
    def dragMoveEvent(self, event):

        if event.mimeData().hasFormat('application/x-qabstractitemmodeldatalist') and not isinstance(event, QtGui.QDropEvent):
            event.accept()
        return QtGui.QTreeWidget.dragMoveEvent(self, event)
    def dropEvent(self, event):
        if event.mimeData().hasFormat('application/x-qabstractitemmodeldatalist'):    
            bytearray = event.mimeData().data('application/x-qabstractitemmodeldatalist')      
            datastream = QtCore.QDataStream(bytearray, QtCore.QIODevice.ReadOnly)
            print(3306, bytearray.data())       
            item = QtGui.QTreeWidgetItem()
            item.setFlags(QtCore.Qt.ItemFlag.ItemIsEditable|QtCore.Qt.ItemFlag.ItemIsEnabled|QtCore.Qt.ItemFlag.ItemIsSelectable|QtCore.Qt.ItemIsDragEnabled|QtCore.Qt.ItemIsDropEnabled)

            item.read(datastream)
            self.addTopLevelItem(item)
def main():
    try:
        QtGui.QApplication([])
    except Exception as e:
        print(e)

    mw = MainWindow()
    mw.show()
    sys.exit(QtGui.QApplication.exec_())
if __name__ == "__main__":
    main()

Answer 1

It is not necessary to implement your own drag-and-drop method between in QTreeWidget, you just have to configure it correctly:

from PySide import QtCore, QtGui

import sys


class MainWindow(QtGui.QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent=None)

        self.sequoia = Sequoia()
        self.baobab = Baobab()
        self.c_widget = QtGui.QWidget()
        h_boxlayout = QtGui.QHBoxLayout(self.c_widget)
        self.setCentralWidget(self.c_widget)
        h_boxlayout.addWidget(self.sequoia, 30)
        h_boxlayout.addWidget(self.baobab, 70)


class Sequoia(QtGui.QTreeWidget):
    def __init__(self, parent=None):
        super(Sequoia, self).__init__(parent=None)
        self.setColumnCount(2)
        self.setDefaultDropAction(QtCore.Qt.CopyAction)
        self.setDragDropMode(QtGui.QAbstractItemView.InternalMove)
        self.setAcceptDrops(True)

        self.sampleitem = QtGui.QTreeWidgetItem()
        self.sampleitem.setText(0, "a")
        self.sampleitem.setText(1, "b")
        self.addTopLevelItem(self.sampleitem)


class Baobab(QtGui.QTreeWidget):
    def __init__(self, parent=None):
        super(Baobab, self).__init__(parent=None)
        self.setColumnCount(2)
        self.setAcceptDrops(True)


def main():
    app = QtGui.QApplication(sys.argv)
    mw = MainWindow()
    mw.show()
    sys.exit(app.exec_())


if __name__ == "__main__":
    main()

If you still want to implement it manually then if we use your perspective a possible solution is:

def dropEvent(self, event):
    if event.mimeData().hasFormat(
        "application/x-qabstractitemmodeldatalist"
    ):

        ba = event.mimeData().data(
            "application/x-qabstractitemmodeldatalist"
        )
        ds = QtCore.QDataStream(
            ba, QtCore.QIODevice.ReadOnly
        )
        i = 0

        item = QtGui.QTreeWidgetItem()
        while not ds.atEnd():
            row = ds.readInt32()
            column = ds.readInt32()
            map_items = ds.readInt32()
            self.addTopLevelItem(item)
            for _ in range(map_items):
                role = ds.readInt32()
                value = ds.readQVariant()
                item.setData(i, role, value)
            i = (i + 1) % self.columnCount()

But the above is forced, a better solution is to use the dropMimeData method of the model:

def dropEvent(self, event):
    if event.mimeData().hasFormat(
        "application/x-qabstractitemmodeldatalist"
    ):

        parent = self.indexAt(event.pos())
        self.model().dropMimeData(
            event.mimeData(), event.dropAction(), 0, 0, parent
        )