在QT中关闭窗口之前获取应用程序退出信号

Question

我有一个带有多个主窗口的 Qt 应用程序，我想在应用程序即将退出时收到一个信号，而所有窗口都还在运行。

QApplication.aboutToQuit 信号对我不起作用，因为它仅在所有窗口关闭后才会触发。

我看到的所有其他答案都建议实现主窗口的 closeEvent() 函数，但我有多个主窗口，我找不到任何方法来区分 CloseEvents 和普通 closeEvent 之间的区别窗口被关闭以及整个应用程序在QMD+Q 之后关闭或在任务栏中使用单击退出或出于任何原因退出时的关闭事件。

只有在整个应用程序即将退出但在任何窗口关闭之前，我如何才能获得信号？

当我按下 Cmd+Q 或右键退出任务栏图标时会发生什么：

1. （此时我想要一个信号）
2. 所有窗口都获得一个 closeEvent()
3. aboutToQuit() 触发
4. 应用退出

我想要的是在任何事情发生之前得到一个信号，并且所有的窗户仍然打开。

编辑：最小示例

from PyQt5.QtGui import QCloseEvent
from PyQt5.QtWidgets import QApplication, QWidget

class Win(QWidget):
    def closeEvent(self, event: QCloseEvent):
        # implementing a custom closeEvent doesn't help me
        # this is called for every normal manual window close and when the application quits
        # I only want to run something when the full application gets shut down, not just this window
        # can't see any way to differentiate between the two
        print("closeEvent", event.type(), event)
        return super().closeEvent(event)


if __name__ == '__main__':
    app = QApplication([])
    app.aboutToQuit.connect(lambda :print("about to quit, this is too late, by now all windows are closed"))

    #What I need
    # app.beforeQuitSignal.connect(lambda :print("signal that it's gonna quit, before any of the windows are closed"))

    #stuff I've tried that didn't work either
    app.quit = lambda *args:print("quit, doesnt get called")
    app.exit = lambda *args:print("exit, doesnt get called")
    app.closeAllWindows = lambda *args:print("closeAllWindows, doesnt get called")

    mainwins = []
    for i in range(5):
        win = Win()
        win.setGeometry(100*i,100*i, 400,400), win.show(), win.raise_()
        mainwins.append(win)

    app.exec_()

Answer 1

如果您想在用户关闭窗口时触发信号，但在最后一个窗口关闭后不立即退出QApplication，您可以使用QApplication.setQuitOnLastWindowClosed()

from PyQt5.QtCore import pyqtSignal
from PyQt5.QtGui import QCloseEvent
from PyQt5.QtWidgets import QApplication, QWidget


class Win(QWidget):
    closing = pyqtSignal()

    def closeEvent(self, event: QCloseEvent):
        print("Window {} closed".format(self))
        self.closing.emit()
        return super().closeEvent(event)


class MyApp(QApplication):
    def __init__(self, *args):
        super(MyApp, self).__init__(*args)

        self.setQuitOnLastWindowClosed(False)
        self.lastWindowClosed.connect(self.onLastClosed)

        self.mainwins = []
        for i in range(5):
            win = Win()
            win.setGeometry(100 * i, 100 * i, 400, 400), win.show(), win.raise_()
            self.mainwins.append(win)

    def onLastClosed(self):
        print("Last windows closed, exiting ...")
        self.exit()


if __name__ == '__main__':
    app = MyApp([])
    app.exec_()

这样，当窗口关闭时，会发出closing() 信号

Answer 2

如果是spontaneous，您可以过滤CloseEvent：

from PyQt5.QtCore import pyqtSignal, QEvent
from PyQt5.QtGui import QCloseEvent
from PyQt5.QtWidgets import QApplication, QWidget


class Win(QWidget):
    closing = pyqtSignal()
    def closeEvent(self, event: QCloseEvent):
        self.closing.emit()
        if event.type() == QEvent.Close and event.spontaneous():
            event.ignore()
        else:
            return super().closeEvent(event)


class MyApp(QApplication):
    def __init__(self, *args):
        super(MyApp, self).__init__(*args)

        self.mainwins = []
        for i in range(5):
            win = Win()
            win.closing.connect(self.beforeQuit)
            win.setGeometry(100 * i, 100 * i, 400, 400), win.show(), win.raise_()
            self.mainwins.append(win)

    def beforeQuit(self):
        print("Exiting")
        # Do what you want here ...
        self.exit()  # Terminate the QApplication

if __name__ == '__main__':
    app = MyApp([])
    app.exec_()

Answer 3

使用installEventFilter在任何窗口关闭之前拦截应用程序的退出事件：

class AppManager(QObject):
    def __init__(self):
        super().__init__()
        qApp.installEventFilter(self)

    def eventFilter(self, obj, event):
        if event.type() == QEvent.Quit:
            self.saveWindowStates()
        return False

    def saveWindowStates(self):
        # code to save the application's state