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

Question

我在这里学习了一个例子(由neuronet编写).我尝试在QTableView中使用这个方法,但是当我更改文本时,会产生这样的错误

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

一旦按下"撤消"按钮,错误就会出现

TypeError:'instancemethod'对象未连接

这是我的代码,谢谢你的帮助.

# 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

从PyQt文档:

Qt使用QVariant类作为任何C++数据类型的包装器.PyQt4允许任何Python对象被包装为QVariant并像任何其他类型一样传递Qt的元对象系统.

如果可以的话,PyQt4会尝试将Python对象转换为C++等价物,以便可以将QVariant传递给不知道Python对象是什么的其他C++代码.

PyQt4的QVariant API版本2将自动将QVariant转换回正确类型的Python对象.

QVariant API的第1版提供了QVariant.toPyObject()方法,以将QVariant转换回正确类型的Python对象.

如果无法进行转换,这两个版本都会引发Python异常.

我猜你是在Python 2.x上,并且PyQt默认使用QVariant API的版本1.它意味着QVariant不会自动转换为另一种类型(这里是a QString),所以你得到一个TypeError.

那么,三个解决方案:

• 使用Python 3.x,默认情况下,您将拥有QVariant的第2版

• sip在导入PyQt之前更改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())
  

一旦纠正,我在你的代码中发现了另一个错误:

TypeError: invalid result type from StandardItem.setData()

这是因为你做return True的setData(),应该返回void(所以在Python中,应该什么都不返回)