python - 从 PyQt5 迁移到 PySide2 时的 QVariant 替代方案

Question

由于以下代码，我在从 PyQt5 切换到 PySide2 时遇到了一些问题:

class EnumModel(QtCore.QAbstractListModel):

    def __init__(self, list_of_enums):
        """
        Enumeration model
        :param list_of_enums: list of enumeration values to show
        """
        QtCore.QAbstractListModel.__init__(self)
        self.items = list_of_enums

    def rowCount(self, parent=QtCore.QModelIndex()):
        return len(self.items)

    def data(self, index, role=QtCore.Qt.DisplayRole):
        if index.isValid() is True:
            if role == QtCore.Qt.DisplayRole:
                return QtCore.QVariant(self.items[index.row()].value[0])
            elif role == QtCore.Qt.ItemDataRole:
                return QtCore.QVariant(self.items[index.row()].value[0])
        return QtCore.QVariant()

代码在 PyQt5 下运行良好。

在迁移过程中，我发现 the official website说:

PySide only supports PyQt's API 2 (see PSEP 101) for details. Therefore Qt classes such as QStrings, QStringLists, and QVariants are not available on PySide. Instead, you should simply use native Python datatypes.

所以解决方案是(我猜)通过str简单地改变QVariant。当我这样做时，类不会抛出任何错误，但它也不显示模型。

事实上 data 函数正在接收 role=13 而不是 role=QtCore.Qt.DisplayRole。

我不知道这是 PySide2 的错误(在 Linux 下有点错误)还是因为其他原因。

一个最小可行的例子是这样的:

from PySide2.QtWidgets import *
from PySide2 import QtCore
from enum import Enum


class SomeEnum(Enum):
    A = 'A'
    B = 'B'
    C = 'C'


class EnumModel(QtCore.QAbstractListModel):

    def __init__(self, list_of_enums):
        """
        Enumeration model
        :param list_of_enums: list of enumeration values to show
        """
        QtCore.QAbstractListModel.__init__(self)
        self.items = list_of_enums

    def rowCount(self, parent=QtCore.QModelIndex()):
        return len(self.items)

    def data(self, index, role=QtCore.Qt.DisplayRole):
        if index.isValid() is True:
            if role == QtCore.Qt.DisplayRole:
                return self.items[index.row()].value[0]
            elif role == QtCore.Qt.ItemDataRole:
                return self.items[index.row()].value[0]
            else:
                print('not recognised')
        return ""


if __name__ == '__main__':
    import sys

    model = EnumModel([SomeEnum.A, SomeEnum.A, SomeEnum.B, SomeEnum.C])

    app = QApplication(sys.argv)
    lst = QListView()
    lst.setModel(model)
    lst.show()
    sys.exit(app.exec_())

Answer 1

问题是，当 View 需要与角色Qt::SizeHintRole (13) 相关的信息时，您向它传递了一个空字符串，而您必须返回 None 或干脆不返回任何内容，因为它会干扰其他角色:

def data(self, index, role=QtCore.Qt.DisplayRole):
    if index.isValid():
        print(role)
        if role == QtCore.Qt.DisplayRole:
            return self.items[index.row()].value[0]
        elif role == QtCore.Qt.ItemDataRole:
            return self.items[index.row()].value[0]
        else:
            print('not recognised')