[英]qt: QTreeView - limit drag and drop to only happen within a particlar grandparent (ancestor)
我有一個QTreeView,其中實現了拖放功能以允許對項目進行重新排序。
給出以下樹的示例:
Food <--fixed
|--Vegetables <--fixed
| |--carrots <-- draggable/parentable
| |--lettuce <-- draggable/parentable
| | |--icebergLettuce <-- draggable but NOT parentable
|--Fruit <-- fixed
| |--apple <-- draggable/parentable
| |--orange <-- draggable/parentable
| |--bloodOrange <-- draggable/parentable
etc...
標記為可拖動的任何內容都可以被拖動。 標記為可育的任何事物都可能具有可拖動項作為子項。 標記為固定的任何東西都是固定的。
我的問題是,我將如何限制物品掉落以留在特定的父母中? 例如,我可以拖動“ bloodOrange”並將其設為“ apple”或“ orange”的子代(甚至只是更改其在“ Fruit”內部的順序位置),但我不能使其成為胡蘿卜的子代或生菜等
我設法正確編碼了所有標志的標志,除了將放置操作限制在特定父級中的那部分之外。 我只是不知道如何捕獲當前拖動的QModelIndex(我可以從中確定父母,祖父母等)
謝謝!
這是我的flags方法的代碼(如果有幫助的話):注:我將頂層子節點稱為Node(即“食物”),將下一層子節點稱為Groups(即“水果”),將最后兩層子節點(即“水果”)稱為生菜和卷心菜都屬於Params。
#---------------------------------------------------------------------------
def flags(self, index):
"""
Returns whether or not the current item is editable/selectable/etc.
"""
if not index.isValid():
return QtCore.Qt.ItemIsEnabled
#by default, you can't do anything
enabled = QtCore.Qt.NoItemFlags
selectable = QtCore.Qt.NoItemFlags
editable = QtCore.Qt.NoItemFlags
draggable = QtCore.Qt.NoItemFlags
droppable = QtCore.Qt.NoItemFlags
#get a pointer to the referenced object
item = index.internalPointer()
#only 'valid' cells may be manipulated ('valid' is defined by the obj)
if item.column_is_valid(index.column()):
#all valid cells are selectable and enabled
selectable = QtCore.Qt.ItemIsSelectable
enabled = QtCore.Qt.ItemIsEnabled
#column 0 cells may occasionally be dragged and dropped
if index.column() == 0:
#drag/drop is only possible if it is a param...
if item.get_obj_type() == 'param':
#...and then only child-less params may be dragged...
if item.get_child_count() == 0:
draggable = QtCore.Qt.ItemIsDragEnabled
#...and only params with a group as parent may be dropped on
if item.get_parent().get_obj_type() == "group":
droppable = QtCore.Qt.ItemIsDropEnabled
#all other valid columns > 0 may be edited (no drag or drop)
else:
editable = QtCore.Qt.ItemIsEditable
#return our flags.
return enabled | selectable| editable| draggable| droppable
如果您希望拖動鼠標懸停在某些行上時顯示“不允許”圖標,我相信您不能從模型中做到這一點。 您必須在View窗口小部件上攔截dragEnter / Move事件。
但是,dropMimeData()可以返回False,指示拒絕放置。
請注意(在我的Qt版本中)qdnd_win中存在一個有關模型拒絕的液滴的錯誤。 這是我根據一些原始資料開發的解決方法; 這是在我的QTreeView子類上定義的方法:
def dropEvent(self, evt):
QTreeView.dropEvent(self, evt)
if not evt.isAccepted():
# qdnd_win.cpp has weird behavior -- even if the event isn't accepted
# by target widget, it sets accept() to true, which causes the executed
# action to be reported as "move", which causes the view to remove the
# source rows even though the target widget didn't like the drop.
# Maybe it's better for the model to check drop-okay-ness during the
# drag rather than only on drop; but the check involves not-insignificant work.
evt.setDropAction(Qt.IgnoreAction)
(請注意,“無關緊要的工作”我的意思是“我不想打擾這些事件” :-)
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