小部件的“销毁"信号未触发(PyQT) [英] Widget's "destroyed" signal is not fired (PyQT)

问题描述

我有一个小部件，它在被销毁后必须进行一些手动清理(停止一些线程).但是由于某种原因，小部件的销毁"信号没有触发.我做了这个小例子来演示这个问题.

I have a widget which would have to do some manual cleanup after it's destroyed (stop some threads). However for some reason the "destroyed" signal of the widget is not firing. I have made this small example that demonstrates the problem.

import sys
from PyQt4 import QtGui

class MyWidget(QtGui.QWidget):
    def __init__(self, parent):
        super(MyWidget, self).__init__(parent)

        def doSomeDestruction():
            print('Hello World!')

        self.destroyed.connect(doSomeDestruction)


class MyWindow(QtGui.QMainWindow):
    def __init__(self):
        super(MyWindow, self).__init__()

        self.widget = MyWidget(self)

app = QtGui.QApplication(sys.argv)
window = MyWindow()
window.show()
ret = app.exec_()
sys.exit(ret)

我希望它打印Hello World！"当主窗口关闭时.但是，它不会打印任何内容.

I expected it to print "Hello World!" when the main window is closed. However, it doesn't print anything.

推荐答案

经过几次尝试后，我发现如果您在类外声明 doSomeDestruction，它 可以工作.(见底部)
但我不知道为什么.如这个答案中所写，这是因为在发出destroy()时，小部件不再是QWidget，而只是一个QObject(因为destroy()是从~QObject发出的).
这意味着当你的函数被调用时，如果你在类中编写它，它已经被删除了.(另请查看 此处在 qt-interest 邮件列表中:<代码>好的，我很抱歉这个愚蠢的问题.信号发出了，但是由于明显的原因没有调用插槽，那是因为对象已经被删除了.)

After a few tries I found out that it works if you declare the doSomeDestruction outside the class. (see at the bottom)
But I don't know why. As written in this answer, this is because At the point destroyed() is emitted, the widget isn't a QWidget anymore, just a QObject (as destroyed() is emitted from ~QObject).
This means when your function would be called it is already deleted if you write it in the class. (look also here in the qt-interest mailing list: Ok , I am sorry for stupid question. The signal is emitted, but the slot is not called for the obvious reason, that is because object is already deleted. )

我发现了两种使它真正起作用的方法:

I've found two ways make it really work:

1. 在ret = app.exec_()之后添加一个简单的del window.

2. 在主窗口(不是小部件)中设置 WA_DeleteOnClose 属性:
   在程序顶部:

1. add a simple del window after ret = app.exec_().

2. Set the WA_DeleteOnClose attribute in the main window (not the widget):
   At the top of the program:

from PyQt4 import QtCore

改变的__init__函数:

class MyWindow(QtGui.QMainWindow):
    def __init__(self):
        super(MyWindow, self).__init__()
        self.setAttribute(QtCore.Qt.WA_DeleteOnClose, True)
        self.widget = MyWidget(self)

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