TypeError: PyQt4.QtCore.QVariantAnimation表示一个C++抽象类，不能实例化

Question

我有一个PyQt5片段，我正试图将其转换为PyQt4。PyQt5版本工作得很好，但是当我试图转换为PyQt4时，我会得到这个错误。我删除了QtWidgets，但仍然收到此错误。我还试图实例化self.animation = QtCore.QVariantAnimation()，但仍然得到相同的错误。

Traceback (most recent call last):
  File ".\test1.py", line 29, in <module>
    lineedit = LineEdit()
  File ".\test1.py", line 13, in __init__
    valueChanged=self.on_color_change,
TypeError: PyQt4.QtCore.QVariantAnimation represents a C++ abstract class and cannot be instantiated

工作PyQt5版本

import sys
from PyQt5 import QtCore, QtGui, QtWidgets

class LineEdit(QtWidgets.QLineEdit):
    def __init__(self):
        super(LineEdit, self).__init__()
        self.textChanged.connect(self.start_animation)

        self.animation = QtCore.QVariantAnimation(
            startValue=QtGui.QColor(255, 127, 127),
            endValue=QtGui.QColor(255, 255, 255),
            duration=1000,
            valueChanged=self.on_color_change,
        )

    @QtCore.pyqtSlot()
    def start_animation(self):
        if self.animation.state() == QtCore.QAbstractAnimation.Running:
            self.animation.stop()
        self.animation.start()

    @QtCore.pyqtSlot(QtCore.QVariant)
    @QtCore.pyqtSlot(QtGui.QColor)
    def on_color_change(self, color):
        self.setStyleSheet("QLineEdit{background-color: %s}" % (color.name(),))

if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    lineedit = LineEdit()
    lineedit.show()
    sys.exit(app.exec_())

破碎的PyQt4版本

import sys
from PyQt4 import QtCore, QtGui

class LineEdit(QtGui.QLineEdit):
    def __init__(self):
        super(LineEdit, self).__init__()
        self.textChanged.connect(self.start_animation)

        self.animation = QtCore.QVariantAnimation(
            startValue=QtGui.QColor(255, 127, 127),
            endValue=QtGui.QColor(255, 255, 255),
            duration=1000,
            valueChanged=self.on_color_change,
        )

    @QtCore.pyqtSlot()
    def start_animation(self):
        if self.animation.state() == QtCore.QAbstractAnimation.Running:
            self.animation.stop()
        self.animation.start()

    @QtCore.pyqtSlot(QtCore.QVariant)
    @QtCore.pyqtSlot(QtGui.QColor)
    def on_color_change(self, color):
        self.setStyleSheet("QLineEdit{background-color: %s}" % (color.name(),))

if __name__ == "__main__":
    app = QtGui.QApplication(sys.argv)
    lineedit = LineEdit()
    lineedit.show()
    sys.exit(app.exec_())

有人知道怎么解决这个问题吗？

Answer 1

在Qt4 updateCurrentValue()中，是一个需要实现的纯虚拟方法，在Qt5情况下，它只是一个虚拟方法，在第一种情况下，C++强制实现它，但是随着Qt5的改变，它不再需要实现，所以解决方案是实现该方法：

# ...
class VariantAnimation(QtCore.QVariantAnimation):
    def updateCurrentValue(self, value):
        pass


class LineEdit(QtGui.QLineEdit):
    def __init__(self):
        super(LineEdit, self).__init__()
        self.textChanged.connect(self.start_animation)

        self.animation = VariantAnimation(
            startValue=QtGui.QColor(255, 127, 127),
            endValue=QtGui.QColor(255, 255, 255),
            duration=1000,
            valueChanged=self.on_color_change,
        )

    # ...

    @QtCore.pyqtSlot(QtCore.QVariant)
    @QtCore.pyqtSlot(QtGui.QColor)
    def on_color_change(self, color):
        if isinstance(color, QtCore.QVariant):
            color = QtGui.QColor(color)
        self.setStyleSheet("QLineEdit{background-color: %s}" % (color.name(),))
    # ...