错误案例（QPaintDevice: Cannot destroy paint device that is being painted）

今天，帮一网友改程序，非常郁闷，一个小bug找了很就，于是把程序写下，作下记录：

程序的功能大致是，点击四个按钮，分别显示四个图片在窗口!

先上程序：

__author__ = 'Administrator'
try:from PySide import QtCorefrom PySide import QtGui
except ImportError:from PyQt4 import QtCorefrom PyQt4 import QtGui
class Mainwindow(QtGui.QWidget):def __init__(self):super(Mainwindow,self).__init__()self.img1=QtGui.QImage("D:\myicon.jpg")self.img2=QtGui.QImage("D:\one.jpg")self.img3=QtGui.QImage("D:\m2yicon.jpg")self.img4=QtGui.QImage("D:\myi3con.jpg")button1 = QtGui.QPushButton("1")button2 = QtGui.QPushButton("2")button3 = QtGui.QPushButton("3")button4 = QtGui.QPushButton("4")button1.clicked.connect(self.slotbutton1)button2.clicked.connect(self.slotbutton2)button3.clicked.connect(self.slotbutton3)button4.clicked.connect(self.slotbutton4)buttonlayout = QtGui.QHBoxLayout()buttonlayout.addWidget(button1)buttonlayout.addWidget(button2)buttonlayout.addWidget(button3)buttonlayout.addWidget(button4)mainlayout = QtGui.QVBoxLayout()mainlayout.addLayout(buttonlayout)self.setLayout(mainlayout)self.showimg = self.img1self.resize(self.showimg.width(),self.height())def paintEvent(self, e):painter = QtGui.QPainter(self)painter.drawImage(0,0,self.showimg)self.resize(self.showimg.width(),self.height())def slotbutton1(self):self.showimg = self.img1self.repaint()def slotbutton2(self):self.showimg = self.img2self.repaint()def slotbutton3(self):self.showimg = self.img3self.repaint()def slotbutton4(self):self.showimg = self.img4self.repaint()if __name__ == '__main__':import sysapp = QtGui.QApplication(sys.argv)mainwindow = Mainwindow()mainwindow.show()sys.exit(app.exec_())

我遇到的错误是什么呢？

下面这个代码片段是我改过的

       painter = QtGui.QPainter(self)painter.drawImage(0,0,self.showimg)

我没改之前是什么呢：

       self.painter = QtGui.QPainter(self)self.painter.drawImage(0,0,self.showimg)

错误信息是:QPaintDevice: Cannot destroy paint device that is being painted

我对self.a和a的理解是，带了self的话，会是a的作用域变为整个对象域，不加的话，就是整个函数域

所以，我们得记住重载paintEvent()函数的时候，里面的Qpainter()对象一定不能带self，不然就会出现析构错误.

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