在拖放中保留 QStandardItem 子类

Preserve QStandardItem subclasses in drag and drop(在拖放中保留 QStandardItem 子类)

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 并检查它的类时，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.

如何在拖放时保持项目的原始类?

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

推荐答案

如这个答案中所述，您可以使用setItemPrototype 为模型提供项目工厂.但是，正如答案中所述，在拖放操作期间仅传输某些类型的信息.对于QStandardItem，这意味着只有项目标志 和 项目数据.如果使用多个子类，则无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.

这意味着如果您需要区分不同的项目类型，则不应使用多个 QStandardItem 子类.相反，您应该使用单个子类并重新实现 QStandardItem.type 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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