保存QStandardItem子类的拖放 [英] Preserve QStandardItem subclasses in drag and drop

问题描述

我有：

self.treeView = QTreeView()
self.treeView.setObjectName("testView")
self.treeView.setDragDropMode(QAbstractItemView.InternalMove)
self.treeView.setSelectionMode(QAbstractItemView.ExtendedSelection)

itemA = SubclassQStandardItemA(self)
itemB = SubcalssQStandardItemB(self)

self.model = QStandardItemModel()
self.treeView.setModel(self.model)

self.model.appendRow(itemA)
self.model.appendRow(itemB)

当我将itemB移动到itemA并检查其类时， ItemB不再是SubclassQStandardItemB，而是QStandardItem。

When I move itemB to itemA and check its class, ItemB is no longer a SubclassQStandardItemB but a QStandardItem.

当我拖放时，如何保留原始类的项目？

How can I keep the original class of the item when I drag and drop?

推荐答案

正如这个答案所解释的那样，您可以使用 setItemPrototype 来提供项目工厂一个模型。然而，正如答案中所述，在拖放操作期间只传送某些种类的信息。对于 QStandardItem ，这意味着只有项目标记和项目数据。如果有多个子类被使用，则没有办法保留项目的特定子类。一个模型只能有一个原型，用于Qt内部创建的所有项目。

As explained in this answer, you can use setItemPrototype to provide an item factory for a model. However, as also stated in the answer, only certain kinds of information are transferred during a drag and drop operation. For a QStandardItem, this means only the item flags and item data. There is no way to preserve the specific subclass of the item if there are multiple subclasses being used. A model can have only one prototype, and that is used for all items that are created internally by Qt.

这意味着您不应该使用多个 QStandardItem 子类，如果您需要区分不同的项目类型。相反，您应该使用单个子类，并重新实施 QStandardItem.type 以区分它们：

This means you should not use multiple QStandardItem subclasses if you need to distinguish between different item types. Instead, you should use a single subclass and reimplement QStandardItem.type to distinguish between them:

class MyItem(QtGui.QStandardItem):
    TypeItemA = QtGui.QStandardItem.UserType
    TypeItemB = QtGui.QStandardItem.UserType + 1
    TypeItemC = QtGui.QStandardItem.UserType + 2

    def clone(self):
        return MyItem()

    def type(self):
        return self.data(QtCore.Qt.UserRole + 1000)

    def setType(self, value):
        self.setData(QtCore.Qt.UserRole + 1000, value)

...

itemA = MyItem(self)
itemA.setType(MyItem.TypeItemA)
itemB = MyItem(self)
itemB.setType(MyItem.TypeItemB)

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