无法从 QtGui.QStandardItem 发出信号

Question

如果复选框被修改，我正在尝试覆盖 QTreeView 以处理调整父母和孩子。但是我无法发出信号，我不确定是不是因为我试图继承 QtGui 而不是 QtWidgets。

下面是触发错误的代码：

class QStandardItem(QtGui.QStandardItem):
    someSignal = QtCore.Signal()
    def __init__(self, *args, **kwargs):
        QtGui.QStandardItem.__init__(self, *args, **kwargs)
        self.someSignal.emit()

>>> QStandardItem()
# AttributeError: 'PySide2.QtCore.Signal' object has no attribute 'emit' # 

这是我当前的代码仅供参考：

class QStandardItem(QtGui.QStandardItem):
    checkStateChanged = QtCore.Signal(object)

    def __init__(self, *args, **kwargs):
        QtGui.QStandardItem.__init__(self, *args, **kwargs)

    def setData(self, data, role):
        if role == QtCore.Qt.CheckStateRole:
            self.checkStateChanged.emit(self)
        QtGui.QStandardItem.setData(self, data, role)


class QTreeView(QtWidgets.QTreeView):
    def __init__(self, *args, **kwargs):
        QtWidgets.QTreeView.__init__(self, *args, **kwargs)

    #I need to know when to trigger this as it edits other nodes
    def checkStateChanged(self, model_index):
        selected_item = self.model().itemFromIndex(model_index)
        check_state = selected_item.checkState()

        #Handle child nodes
        for i in range(selected_item.rowCount()):
            child_item = selected_item.child(i)
            if child_item.isCheckable():
                child_item.setCheckState(check_state)

        #Handle parent nodes
        parent_item = selected_item.parent()
        check_states = {QtCore.Qt.Checked: 0,
                        QtCore.Qt.PartiallyChecked: 1,
                        QtCore.Qt.Unchecked: 2}
        counts = [0, 0, 0]
        if parent_item is not None:
            for i in range(parent_item.rowCount()):
                child_item = parent_item.child(i)
                if child_item.isCheckable():
                    counts[check_states[child_item.checkState()]] += 1
            if counts[0] and not counts[1] and not counts[2]:
                parent_item.setCheckState(QtCore.Qt.Checked)
            elif not counts[0] and not counts[1] and counts[2]:
                parent_item.setCheckState(QtCore.Qt.Unchecked)
            else:
                parent_item.setCheckState(QtCore.Qt.PartiallyChecked)

Answer 1

正如您所指出的，只有从 QObject 继承的类才能发出信号，QStandardItem 不是 QObject，因此会产生这个问题。适当的选择是使用 QStandardItemModel，为此我们覆盖 setData() 方法并建立一个逻辑来验证状态是否已更改，然后使用 itemFromIndex() 方法发出 QStandardItem，该方法返回 QStandardItem，给定QModelIndex.

例子：

from PySide2 import QtCore, QtGui, QtWidgets


class StandardItemModel(QtGui.QStandardItemModel):
    checkStateChanged = QtCore.Signal(QtGui.QStandardItem)

    def setData(self, index, value, role=QtCore.Qt.EditRole):
        if role == QtCore.Qt.CheckStateRole:
            last_value = self.data(index, role)
        val = super(StandardItemModel, self).setData(index, value, role)
        if role == QtCore.Qt.CheckStateRole and val:
            current_value = self.data(index, role)
            if last_value != current_value:
                it = self.itemFromIndex(index)
                self.checkStateChanged.emit(it)
        return val


class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        w = QtWidgets.QTreeView()

        model = StandardItemModel(w)
        w.setModel(model)

        model.checkStateChanged.connect(self.foo_slot)

        for i in range(4):
            top_level = QtGui.QStandardItem("{}".format(i))
            top_level.setCheckable(True)
            model.appendRow(top_level)
            for j in range(5):
                it = QtGui.QStandardItem("{}-{}".format(i, j))
                it.setCheckable(True)
                top_level.appendRow(it)
        w.expandAll()
        self.setCentralWidget(w)

    @QtCore.Slot(QtGui.QStandardItem)
    def foo_slot(self, item):
        print(item.text(), item.checkState())


if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec_())

Answer 2

不是 100% 肯定，但对于 Python，为了定义您自己的信号，您必须使用：

QtCore.pyqtSignal()

此外，您可能还需要继承 QtCore.QObject 才能使用信号

编辑：刚刚看到您使用 pyside，所以放弃第一个解决方案，但继承 QObject 是您的解决方案而不是