How to drag rows in Treeview

[chuanzhen]

Hi,
I have read many posts about the dragging behavior of treeview, all of which are examples of dragging from the outside into treeview. What I want is to drag the rows of treeview to rearrange them, just like an object manager dragging objects.

This post also mentioned some explanations about the drag and drop process, but I am still confused about how to start.

I found an example of code in this post. Can we implement the drag behavior of treeview rows on this basis

import c4d
import weakref

# Be sure to use a unique ID obtained from [URL-REMOVED]
PLUGIN_ID = 1000010  # TEST ID ONLY

# TreeView Column IDs.
ID_CHECKBOX = 1
ID_NAME = 2
ID_OTHER = 3


def TextureObjectIterator(lst):
    for parentTex in lst:
        yield parentTex
        for childTex in TextureObjectIterator(parentTex.GetChildren()):
            yield childTex


class TextureObject(object):
    """
    Class which represent a texture, aka an Item in our list
    """
    texturePath = "TexPath"
    otherData = "OtherData"
    _selected = False
    _open = True

    def __init__(self, texturePath):
        self.texturePath = texturePath
        self.otherData += texturePath
        self.children = []
        self._parent = None

    @property
    def IsSelected(self):
        return self._selected

    def Select(self):
        self._selected = True

    def Deselect(self):
        self._selected = False

    @property
    def IsOpened(self):
        return self._open

    def Open(self):
        self._open = True

    def Close(self):
        self._open = False

    def AddChild(self, obj):
        obj._parent = weakref.ref(self)
        self.children.append(obj)

    def GetChildren(self):
        return self.children

    def GetParent(self):
        if self._parent:
            return self._parent()

        return None

    def __repr__(self):
        return str(self)

    def __str__(self):
        return self.texturePath


class ListView(c4d.gui.TreeViewFunctions):

    def __init__(self):
        self.listOfTexture = list()  # Store all objects we need to display in this list

        # Add some defaults values 
        t1 = TextureObject("T1")
        t2 = TextureObject("T2")
        t3 = TextureObject("T3")
        t4 = TextureObject("T4")

        self.listOfTexture.extend([t1, t2, t3, t4])

    def IsResizeColAllowed(self, root, userdata, lColID):
        return True

    def IsTristate(self, root, userdata):
        return False

    def GetColumnWidth(self, root, userdata, obj, col, area):
        return 80  # All have the same initial width

    def IsMoveColAllowed(self, root, userdata, lColID):
        # The user is allowed to move all columns.
        # TREEVIEW_MOVE_COLUMN must be set in the container of AddCustomGui.
        return True

    def GetFirst(self, root, userdata):
        """
        Return the first element in the hierarchy, or None if there is no element.
        """
        rValue = None if not self.listOfTexture else self.listOfTexture[0]
        return rValue

    def GetDown(self, root, userdata, obj):
        """
        Return a child of a node, since we only want a list, we return None everytime
        """
        children = obj.GetChildren()
        if children:
            return children[0]

        return None

    def GetNext(self, root, userdata, obj):
        """
        Returns the next Object to display after arg:'obj'
        """
        rValue = None

        # If does have a child it means it's a child.
        objParent = obj.GetParent()
        listToSearch = objParent.GetChildren() if objParent is not None else self.listOfTexture

        currentObjIndex = listToSearch.index(obj)
        nextIndex = currentObjIndex + 1
        if nextIndex < len(listToSearch):
            rValue = listToSearch[nextIndex]

        return rValue

    def GetPred(self, root, userdata, obj):
        """
        Returns the previous Object to display before arg:'obj'
        """
        rValue = None

        # If does have a child it means it's a child.
        objParent = obj.GetParent()
        listToSearch = objParent.GetChildren() if objParent is not None else self.listOfTexture

        currentObjIndex = listToSearch.index(obj)
        predIndex = currentObjIndex - 1
        if 0 <= predIndex < len(listToSearch):
            rValue = listToSearch[predIndex]

        return rValue

    def GetId(self, root, userdata, obj):
        """
        Return a unique ID for the element in the TreeView.
        """
        return hash(obj)

    def Select(self, root, userdata, obj, mode):
        """
        Called when the user selects an element.
        """
        if mode == c4d.SELECTION_NEW:
            for tex in self.listOfTexture:
                tex.Deselect()
            obj.Select()
        elif mode == c4d.SELECTION_ADD:
            obj.Select()
        elif mode == c4d.SELECTION_SUB:
            obj.Deselect()

    def IsSelected(self, root, userdata, obj):
        """
        Returns: True if *obj* is selected, False if not.
        """
        return obj.IsSelected

    def SetCheck(self, root, userdata, obj, column, checked, msg):
        """
        Called when the user clicks on a checkbox for an object in a
        `c4d.LV_CHECKBOX` column.
        """
        if checked:
            obj.Select()
        else:
            obj.Deselect()

    def IsChecked(self, root, userdata, obj, column):
        """
        Returns: (int): Status of the checkbox in the specified *column* for *obj*.
        """
        if obj.IsSelected:
            return c4d.LV_CHECKBOX_CHECKED | c4d.LV_CHECKBOX_ENABLED
        else:
            return c4d.LV_CHECKBOX_ENABLED

    def IsOpened(self, root, userdata, obj):
        """
        Returns: (bool): Status If it's opened = True (folded) or closed = False.
        """
        # If there is some children
        return obj.IsOpened

    def Open(self, root, userdata, obj, onoff):
        """
        Called when the user clicks on a folding state of an object to display/hide its children
        """
        if onoff:
            obj.Open()

        else:
            obj.Close()

    def GetName(self, root, userdata, obj):
        """
        Returns the name to display for arg:'obj', only called for column of type LV_TREE
        """
        return str(obj)  # Or obj.texturePath

    def DrawCell(self, root, userdata, obj, col, drawinfo, bgColor):
        """
        Draw into a Cell, only called for column of type LV_USER
        """
        if col == ID_OTHER:
            name = obj.otherData
            geUserArea = drawinfo["frame"]
            w = geUserArea.DrawGetTextWidth(name)
            h = geUserArea.DrawGetFontHeight()
            xpos = drawinfo["xpos"]
            ypos = drawinfo["ypos"] + drawinfo["height"]
            drawinfo["frame"].DrawText(name, xpos, int(ypos - h * 1.1))

    def DoubleClick(self, root, userdata, obj, col, mouseinfo):
        """
        Called when the user double-clicks on an entry in the TreeView.

        Returns:
          (bool): True if the double-click was handled, False if the
            default action should kick in. The default action will invoke
            the rename procedure for the object, causing `SetName()` to be
            called.
        """
        c4d.gui.MessageDialog("You clicked on " + str(obj))
        return True

    def DeletePressed(self, root, userdata):
        "Called when a delete event is received."
        for tex in reversed(list(TextureObjectIterator(self.listOfTexture))):
            if tex.IsSelected:
                listToRemove = objParent.GetChildren() if objParent is not None else self.listOfTexture
                listToRemove.remove(tex)

    def DragStart(self, root: object, userdata: object, obj: object) -> int:
        print("drag")
        c4d.gui.SetMousePointer(c4d.MOUSE_INSERTMOVE)
        return c4d.TREEVIEW_DRAGSTART_ALLOW | c4d.TREEVIEW_DRAGSTART_SELECT

    def SetDragObject(self, root: object, userdata: object, obj: object) -> None:
        pass

class TestDialog(c4d.gui.GeDialog):
    _treegui = None  # Our CustomGui TreeView
    _listView = ListView()  # Our Instance of c4d.gui.TreeViewFunctions

    def CreateLayout(self):
        # Create the TreeView GUI.
        customgui = c4d.BaseContainer()
        customgui.SetBool(c4d.TREEVIEW_BORDER, c4d.BORDER_THIN_IN)
        customgui.SetBool(c4d.TREEVIEW_HAS_HEADER, True)  # True if the tree view may have a header line.
        customgui.SetBool(c4d.TREEVIEW_HIDE_LINES, False)  # True if no lines should be drawn.
        customgui.SetBool(c4d.TREEVIEW_MOVE_COLUMN, True)  # True if the user can move the columns.
        customgui.SetBool(c4d.TREEVIEW_RESIZE_HEADER, True)  # True if the column width can be changed by the user.
        customgui.SetBool(c4d.TREEVIEW_FIXED_LAYOUT, True)  # True if all lines have the same height.
        customgui.SetBool(c4d.TREEVIEW_ALTERNATE_BG, True)  # Alternate background per line.
        customgui.SetBool(c4d.TREEVIEW_CURSORKEYS, True)  # True if cursor keys should be processed.
        customgui.SetBool(c4d.TREEVIEW_NOENTERRENAME, False)  # Suppresses the rename popup when the user presses enter.
        customgui.SetBool(c4d.TREEVIEW_NO_MULTISELECT, True)

        self._treegui = self.AddCustomGui(1000, c4d.CUSTOMGUI_TREEVIEW, "", c4d.BFH_SCALEFIT | c4d.BFV_SCALEFIT, 300,
                                          300, customgui)
        if not self._treegui:
            print("[ERROR]: Could not create TreeView")
            return False

        self.AddButton(1001, c4d.BFH_CENTER, name="Add")
        self.AddButton(1002, c4d.BFH_CENTER, name="Add Child to selected")
        return True

    def InitValues(self):
        # Initialize the column layout for the TreeView.
        layout = c4d.BaseContainer()
        layout.SetLong(ID_CHECKBOX, c4d.LV_CHECKBOX)
        layout.SetLong(ID_NAME, c4d.LV_TREE)
        layout.SetLong(ID_OTHER, c4d.LV_USER)
        self._treegui.SetLayout(3, layout)

        # Set the header titles.
        self._treegui.SetHeaderText(ID_CHECKBOX, "Check")
        self._treegui.SetHeaderText(ID_NAME, "Name")
        self._treegui.SetHeaderText(ID_OTHER, "Other")
        self._treegui.Refresh()

        # Set TreeViewFunctions instance used by our CUSTOMGUI_TREEVIEW
        self._treegui.SetRoot(self._treegui, self._listView, None)
        return True

    def Command(self, id, msg):
        # Click on button
        if id == 1001:
            # Add data to our DataStructure (ListView)
            newID = len(self._listView.listOfTexture) + 1
            tex = TextureObject("T{}".format(newID))
            self._listView.listOfTexture.append(tex)

            # Refresh the TreeView
            self._treegui.Refresh()

        elif id == 1002:
            for parentTex in TextureObjectIterator(self._listView.listOfTexture):
                if not parentTex.IsSelected:
                    continue

                newID = len(parentTex.GetChildren()) + 1
                tex = TextureObject("T{0}.{1}".format(str(parentTex), newID))
                parentTex.AddChild(tex)

            # Refresh the TreeView
            self._treegui.Refresh()

        return True


def main():
    global dialog
    dialog = TestDialog()
    dialog.Open(c4d.DLG_TYPE_ASYNC, defaulth=600, defaultw=600)


if __name__ == "__main__":
    main()

Thanks for your help