在QComboBox中显示树模型的分支

Question

免责声明:我为这个话题找到了不同的类似答案，但我找不到解决我的问题的答案。

我有下面的源代码模型结构，它由一个单列的无头QTreeView显示

- Cat 1
|-- Cat1_El1
|-- ...
|-- Cat1_ElL
...
- Cat N
|-- CatN_El1
|-- ...
|-- CatN_ElM

视图和源模型工作得很好。每个低级项目都是由用户动态创建的，而类别则是硬编码的。

现在，核心问题如下:基于某个条件，我可以通过实例化的代理模型的额外属性轻松管理，我希望在QComboBox中显示特定类别的所有项。我想过重新实现QAbstractProxyModel，但我面临着一些麻烦，无法理解如何重新实现Qt Doc声明的mapFromSource和mapToSource这两个方法。我想出来的东西如下所示。我所有的怀疑和推断都被报告为评论，因为我认为它更清晰。注意，我是用Python语言编写代码，使用PyQt5，但实际上我更感兴趣的是如何重新实现代理的概念，而不是代码本身(因此，C++代码也可以很好地工作)

class GWModulesComboProxy(QIdentityProxyModel):
    # This re-implements the basic proxy structure
    def __init__(self, moduleType : CategoriesType, parent: Optional[QObject]) -> None:
        # `CategoriesType` --> See later `ComboProxyCatN`
        self.moduleType = moduleType
        super().__init__(parent)

    def index(self, row: int, column: int, parent: QModelIndex) -> QModelIndex:
    #   Based upon the crash of the model when clicking on the combobox, I'm inferring that I should re-implementing 
    #   this method and call, FROM it, the `mapToSource`. But I can't figure out how
        pass

    def mapFromSource(self, sourceIndex: QModelIndex) -> QModelIndex:
        if not sourceIndex.isValid():
            return QModelIndex()
        
        # If the node is a root node (i.e. a Cathegory itself), it will never show up into the ComboBox
        if not sourceIndex.parent().isValid():
            return QModelIndex()
        
        # Into the source model, the root nodes are ordered against the IntEnum CategoriesType --> See later `ComboProxyCatN`
        if sourceIndex.parent().row() == self.moduleType:
            return sourceIndex
        
        return QModelIndex()

    def mapToSource(self, proxyIndex: QModelIndex) -> QModelIndex:
        if not proxyIndex.isValid():
            return QModelIndex()

        parent = self.sourceModel().index(self.moduleType, 1, QModelIndex()) 
        return self.sourceModel().index(proxyIndex.row(), proxyIndex.column(), parent)


        
    def data(self, proxyIndex: QModelIndex, role: int) -> Any:
    #   I was guessing that re-implementing `data` was meaningless since the data should be already taken from the source
    #       by means of the mapper methods. Am I correct?
        pass

    def columnCount(self, parent: QModelIndex) -> int:
        return 1

class ComboProxyCatN(ComboProxy):
    # Just an example how to manage the specific Category N
    def __init__(self, parent: Optional[QObject]) -> None:
        # CategoriesType is an IntEnum that stores the different cathegories
        super().__init__(CategoriesType.CatN, parent)

Answer 1

要显示树的分支，不需要使用代理模型，而是必须通过QComboBox的setRootModelIndex()方法来指示根。

下面的示例显示了类别"Cat 5“的分支：

import random

from PyQt5 import QtCore, QtGui, QtWidgets


if __name__ == "__main__":
    import sys

    app = QtWidgets.QApplication(sys.argv)

    model = QtGui.QStandardItemModel()

    for i in range(1, 10):
        root_item = QtGui.QStandardItem(f"Cat {i}")
        model.appendRow(root_item)
        for j in range(1, random.randrange(5, 10)):
            child_item = QtGui.QStandardItem(f"Cat{i}_El{j}")
            root_item.appendRow(child_item)

    view = QtWidgets.QTreeView()
    view.setModel(model)
    view.expandAll()

    category = "Cat 5"

    root_index = QtCore.QModelIndex()
    indexes = model.match(
        model.index(0, 0), QtCore.Qt.DisplayRole, category, flags=QtCore.Qt.MatchExactly
    )
    if indexes:
        root_index = indexes[0]

    # or fifth row
    # root_index = model.index(4, 0)

    combobox = QtWidgets.QComboBox()
    combobox.setModel(model)
    combobox.setRootModelIndex(root_index)
    combobox.setCurrentIndex(0)

    widget = QtWidgets.QWidget()
    lay = QtWidgets.QVBoxLayout(widget)
    lay.addWidget(view)
    lay.addWidget(combobox)
    widget.resize(640, 480)
    widget.show()

    sys.exit(app.exec_())