PySide2：不退出APP就无法关闭QMessageBox

Question

这是一段小代码，其中我有一个连接到 ftp 服务器并显示消息框的线程。我不明白为什么 msgBoxWait 对话框一关闭，应用程序就崩溃了（在 FTP 线程之前终止）。

我猜这是因为它是最后显示的 window，但是，添加 QEventLoop 并不能解决问题。你能帮帮我吗？

# coding: utf-8

import sys
import random
from PySide2 import QtCore, QtWidgets, QtGui


class Logic():
    def __init__(self):
        self.msgBoxWait = QtWidgets.QMessageBox()
        self.ftpThread = FtpThread()
        self.isConnected = False
        self.loop = QtCore.QEventLoop()

    def run(self):
        self.ftpThread.sigIsConnected.connect(self.ftpConnected, QtCore.Qt.QueuedConnection)
        self.ftpThread.finished.connect(self.ftpFinished, QtCore.Qt.QueuedConnection)
        self.ftpThread.sigError.connect(self.ftpError, QtCore.Qt.QueuedConnection)
        self.ftpThread.start()

        QtCore.QTimer.singleShot(200, self.showWaitMsgBox)

        self.loop.exec_()

    def showWaitMsgBox(self):
        self.msgBoxWait.setWindowTitle("Waiting")
        self.msgBoxWait.setText("""Waiting for ftp connection""")
        if not self.isConnected:
            self.msgBoxWait.exec()

    def ftpConnected(self):
        print("connected")
        self.isConnected = True
        self.msgBoxWait.close()  # <- crash here or when I click on the close button

    def ftpFinished(self):
        print("finished")
        self.ftpThread = None
        self.loop.quit()

    def ftpError(self, title, message):
        QtWidgets.QMessageBox.critical(None, title, message)


class FtpThread(QtCore.QThread):
    sigIsConnected = QtCore.Signal()
    sigError = QtCore.Signal(str, str)

    def run(self):
        QtCore.QThread.sleep(2)
        self.sigIsConnected.emit()
        QtCore.QThread.sleep(1)
        self.sigError.emit("error", "An error appened")
        QtCore.QThread.sleep(3)


if __name__ == "__main__":
    app = QtWidgets.QApplication([])

    logic = Logic()
    QtCore.QTimer.singleShot(0, logic.run)

    sys.exit(app.exec_())

Answer 1

默认情况下，Qt 配置为如果最后一个 window 关闭，应用程序将结束，因为这通常是预期的行为，但您的情况并非如此，因为有时您需要继续运行即使没有打开windows。解决方案是将 quitOnLastWindowClosed 属性设置为 False:

# coding: utf-8

import sys
import random
from PySide2 import QtCore, QtWidgets, QtGui


class Logic:
    def __init__(self):
        self.msgBoxWait = QtWidgets.QMessageBox()
        self.ftpThread = FtpThread()
        self.isConnected = False

    def run(self):
        self.ftpThread.sigIsConnected.connect(
            self.ftpConnected, QtCore.Qt.QueuedConnection
        )
        self.ftpThread.finished.connect(self.ftpFinished, QtCore.Qt.QueuedConnection)
        self.ftpThread.sigError.connect(self.ftpError, QtCore.Qt.QueuedConnection)
        self.ftpThread.start()

        QtCore.QTimer.singleShot(200, self.showWaitMsgBox)

    def showWaitMsgBox(self):
        self.msgBoxWait.setWindowTitle("Waiting")
        self.msgBoxWait.setText("""Waiting for ftp connection""")
        if not self.isConnected:
            self.msgBoxWait.exec()

    def ftpConnected(self):
        print("connected")
        self.isConnected = True
        self.msgBoxWait.close()

    def ftpFinished(self):
        print("finished")
        self.ftpThread = None
        <b># QtCore.QCoreApplication.quit() should be used
        # to close the entire application if necessary
        QtCore.QCoreApplication.quit()</b>

    def ftpError(self, title, message):
        QtWidgets.QMessageBox.critical(None, title, message)


class FtpThread(QtCore.QThread):
    sigIsConnected = QtCore.Signal()
    sigError = QtCore.Signal(str, str)

    def run(self):
        QtCore.QThread.sleep(2)
        self.sigIsConnected.emit()
        QtCore.QThread.sleep(1)
        self.sigError.emit("error", "An error appened")
        QtCore.QThread.sleep(3)


if __name__ == "__main__":
    app = QtWidgets.QApplication([])
    <b>app.setQuitOnLastWindowClosed(False)</b>

    logic = Logic()
    QtCore.QTimer.singleShot(0, logic.run)

    sys.exit(app.exec_())

PySide2：不退出APP就无法关闭QMessageBox

PySide2 : cannot close a QMessageBox without quitting the APP

python

qthread

pyside2