QStandardItem.setText(QString) 具有意外类型 'QVariant'？

Question

我在学习了一个例子（neuronet写的），我尝试在QTableView中使用这个方法，但是当我更改文本时，会出现这样的错误

TypeError: QStandardItem.setText(QString): 参数 1 具有意外类型 'QVariant'.

一旦我按下 'undo' 按钮，错误将是

TypeError: 'instancemethod' 对象未连接

这是我的代码，感谢您的帮助。

# coding:utf-8
# coding:utf-8
from PyQt4 import QtGui, QtCore
import sys
class CommandTextEdit(QtGui.QUndoCommand):
    def __init__(self, table, item, oldText, newText, description):
        QtGui.QUndoCommand.__init__(self, description)
        self.item = item
        self.table = table
        self.oldText = oldText
        self.newText = newText

    def redo(self):
        self.item.model().itemDataChanged.disconnect(self.table.itemDataChangedSlot)
        self.item.setText(self.newText)
        self.item.model().itemDataChanged.connect(self.table.itemDataChangedSlot)

    def undo(self):
        self.item.model().itemDataChanged.disconnect(self.table.itemDataChangedSlot)
        self.item.setText(self.oldText)
        self.item.model().itemDataChanged.connect(self.table.itemDataChangedSlot)

class StandardItemModel(QtGui.QStandardItemModel):
    itemDataChanged = QtCore.pyqtSignal(object, object, object, object)

class StandardItem(QtGui.QStandardItem):
    def setData(self, newValue, role=QtCore.Qt.UserRole + 1):
        if role == QtCore.Qt.EditRole:
            oldValue = self.data(role)
            QtGui.QStandardItem.setData(self, newValue, role)
            model = self.model()
            #only emit signal if newvalue is different from old
            if model is not None and oldValue != newValue:
                model.itemDataChanged.emit(self, oldValue, newValue, role)
            return True
        QtGui.QStandardItem.setData(self, newValue, role)
class undoTable(QtGui.QWidget):
    def __init__(self, parent = None):
        QtGui.QWidget.__init__(self, parent = None)
        self.setAttribute(QtCore.Qt.WA_DeleteOnClose)
        self.view = QtGui.QTableView()
        self.model = self.createModel()
        self.view.setModel(self.model)
        self.undoStack = QtGui.QUndoStack(self)
        undoView = QtGui.QUndoView(self.undoStack)
        buttonLayout = self.buttonSetup()
        mainLayout = QtGui.QHBoxLayout(self)
        mainLayout.addWidget(undoView)
        mainLayout.addWidget(self.view)
        mainLayout.addLayout(buttonLayout)
        self.setLayout(mainLayout)
        self.makeConnections()
    def createModel(self):
        model = StandardItemModel(4,4)
        for row in range(4):
            for column in range(4):
                item=StandardItem("(%s,%s)" % (row,column))
                model.setItem(row,column,item)
        return model

    def buttonSetup(self):
        self.undoButton = QtGui.QPushButton("Undo")
        self.redoButton = QtGui.QPushButton("Redo")
        self.quitButton = QtGui.QPushButton("Quit")
        buttonLayout = QtGui.QVBoxLayout()
        buttonLayout.addStretch()
        buttonLayout.addWidget(self.undoButton)
        buttonLayout.addWidget(self.redoButton)
        buttonLayout.addStretch()
        buttonLayout.addWidget(self.quitButton)
        return buttonLayout
    def itemDataChangedSlot(self, item, oldValue, newValue, role):
        if role == QtCore.Qt.EditRole:
            command = CommandTextEdit(self, item, oldValue, newValue,
                "Text changed from '{0}' to '{1}'".format(oldValue, newValue))
            self.undoStack.push(command)
            return True
    def makeConnections(self):
        self.model.itemDataChanged.connect(self.itemDataChangedSlot)
        self.quitButton.clicked.connect(self.close)
        self.undoButton.clicked.connect(self.undoStack.undo)
        self.redoButton.clicked.connect(self.undoStack.redo)

def main():
    app = QtGui.QApplication(sys.argv)
    newtable = undoTable()
    newtable.show()
    sys.exit(app.exec_())

if __name__ == "__main__":
    main()

Answer 1

来自PyQt documentation:

Qt uses the QVariant class as a wrapper for any C++ data type. PyQt4 allows any Python object to be wrapped as a QVariant and passed around Qt’s meta-object system like any other type.

PyQt4 will try to convert the Python object to a C++ equivalent if it can so that the QVariant can be passed to other C++ code that doesn’t know what a Python object is.

Version 2 of PyQt4’s QVariant API will automatically convert a QVariant back to a Python object of the correct type.

Version 1 of the QVariant API provides the QVariant.toPyObject() method to convert the QVariant back to a Python object of the correct type.

Both versions will raise a Python exception if the conversion cannot be done.

我猜你在 Python 2.x，并且 PyQt 默认使用 QVariant API 的版本 1。这意味着 QVariant 不会自动转换为另一种类型（这里是 QString），所以你得到 TypeError.

所以，三个解决方案：

使用Python3.x，默认情况下你会有QVariant

在导入 PyQt 之前用 sip 更改 QVariant 的版本

import sip
sip.setapi('QVariant',2)
from PyQt4 import QtGui, QtCore

使用QVariant.toPyObject()转换为正确的类型
```
self.item.setText(self.newText.toString())
```

更正后，我在您的代码中发现了另一个错误：

TypeError: invalid result type from StandardItem.setData()

这是因为你在 setData() 中做了 return True，这应该是 return void（所以在 Python 中，应该是 return 没什么）

QStandardItem.setText(QString) 具有意外类型 'QVariant'？

QStandardItem.setText(QString) has unexpected type 'QVariant'?

python

qt

pyqt

pyside