Qt5应用调用QMainWindow.close()无法退出，打开QFileDialog后触发该问题

问题表现 #

我在QMainWindow的构造函数中执行了多项初始化操作，包含如下退出相关代码：

self.exitAct = QAction("Exit", self, shortcut="Ctrl+Q", triggered=self.close)
...
self.fileMenu = QMenu("File", self)
self.fileMenu.addAction(self.exitAct)

除此之外我还在构造函数中调用了文件选择对话框，代码如下：

options = QFileDialog.Options()
fileName, _ = QFileDialog.getOpenFileName(self, 'QFileDialog.getOpenFileName()', '',
                                          'Images (*.png *.jpeg *.jpg *.bmp *.gif *.yaml)',
                                          options=options)

当我按下Ctrl+Q快捷键或者点击File->Exit选项时，出现一致的现象：GUI界面正常消失，无任何报错输出，但进程始终驻留不终止。Linux环境下从shell启动应用后，甚至无法通过Ctrl+C（发送SIGINT信号）杀死进程，只能使用kill命令发送SIGTERM信号才能终止进程。
我的应用没有自定义任何close相关方法，直接调用的是原生QMainWindow.close()方法。
最初我完全没有排查方向，后来验证确认是QFileDialog本身导致的该异常，移除QFileDialog相关代码后应用退出逻辑恢复正常。

最小复现代码 #

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import sys, os

from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *

class MainWindow(QMainWindow):

     def __init__(self, fileName=None):
         
          super().__init__()

          self.exitAct = QAction("Exit", self, shortcut="Ctrl+Q", triggered=self.close)
          self.fileMenu = QMenu("File", self)
          self.fileMenu.addAction(self.exitAct)
          self.menuBar().addMenu(self.fileMenu)

          self.openFile()

    
     def openFile(self):
          options = QFileDialog.Options()
          fileName, _ = QFileDialog.getOpenFileName(self, 'QFileDialog.getOpenFileName()', '',
                                                    'Images (*.png *.jpeg *.jpg *.bmp *.gif *.yaml)',
                                                    options=options)
          # load some data ...
          # ...
                        

        
if __name__ == '__main__':
     app = QApplication(sys.argv)
     window = MainWindow()
     window.show()
     sys.exit(app.exec_())

修复后应用组件列表 #

修复问题后执行print(app.allWidgets())的输出如下：

[<PyQt5.QtWidgets.QMenu object at 0x7fb8e6ae49d0>, <PyQt5.QtWidgets.QScrollBar object at 0x7fb8e6ae4b80>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6ae4c10>, <PyQt5.QtWidgets.QMenu object at 0x7fb8e6ae4ca0>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6ae4d30>, <PyQt5.QtWidgets.QPushButton object at 0x7fb8e6ae4160>, <PyQt5.QtWidgets.QScrollBar object at 0x7fb8e6ae4dc0>, <PyQt5.QtWidgets.QLineEdit object at 0x7fb8ee6ea790>, <PyQt5.QtWidgets.QMenu object at 0x7fb8e6ae4790>, <PyQt5.QtWidgets.QLineEdit object at 0x7fb8ee6eae50>, <PyQt5.QtWidgets.QFrame object at 0x7fb8e6ae4e50>, <PyQt5.QtWidgets.QScrollArea object at 0x7fb8ee6ea5e0>, <PyQt5.QtWidgets.QLabel object at 0x7fb8ee6ea670>, <PyQt5.QtWidgets.QLabel object at 0x7fb8e6ae40d0>, <PyQt5.QtWidgets.QToolButton object at 0x7fb8e6ae4ee0>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6ae4f70>, <PyQt5.QtWidgets.QLineEdit object at 0x7fb8ee6eac10>, <PyQt5.QtWidgets.QFrame object at 0x7fb8e6af5040>, <PyQt5.QtWidgets.QScrollBar object at 0x7fb8e6af50d0>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6af5160>, <PyQt5.QtWidgets.QLineEdit object at 0x7fb8ee6ea9d0>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6ae4af0>, <__main__.MainWindow object at 0x7fb8ee6ea160>, <PyQt5.QtWidgets.QLabel object at 0x7fb8e6ae4040>, <PyQt5.QtWidgets.QComboBox object at 0x7fb8ee6ea430>, <PyQt5.QtWidgets.QFrame object at 0x7fb8e6af51f0>, <PyQt5.QtWidgets.QListView object at 0x7fb8e6af5280>, <PyQt5.QtWidgets.QScrollBar object at 0x7fb8e6af5310>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6af53a0>, <__main__.DataArea object at 0x7fb8ee6ea550>, <PyQt5.QtWidgets.QScrollBar object at 0x7fb8e6af5430>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6af54c0>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6af5550>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6af55e0>, <PyQt5.QtWidgets.QScrollBar object at 0x7fb8e6af5670>, <PyQt5.QtWidgets.QMenuBar object at 0x7fb8e6ae4a60>, <PyQt5.QtWidgets.QLabel object at 0x7fb8ee6eadc0>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6af5700>, <PyQt5.QtWidgets.QFrame object at 0x7fb8e6af5790>, <PyQt5.QtWidgets.QListView object at 0x7fb8e6af5820>, <PyQt5.QtWidgets.QComboBox object at 0x7fb8ee6eab80>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6af58b0>, <PyQt5.QtWidgets.QListView object at 0x7fb8e6af5940>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6af59d0>, <PyQt5.QtWidgets.QLabel object at 0x7fb8ee6eaaf0>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6af5a60>, <PyQt5.QtWidgets.QComboBox object at 0x7fb8ee6ea4c0>, <PyQt5.QtWidgets.QScrollBar object at 0x7fb8e6af5af0>, <PyQt5.QtWidgets.QScrollBar object at 0x7fb8e6af5b80>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6af5c10>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6af5ca0>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6af5d30>, <PyQt5.QtWidgets.QLabel object at 0x7fb8ee6eaca0>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6af5dc0>, <PyQt5.QtWidgets.QLabel object at 0x7fb8ee6ea820>, <PyQt5.QtWidgets.QLabel object at 0x7fb8ee6ea940>, <PyQt5.QtWidgets.QScrollBar object at 0x7fb8e6af5e50>, <PyQt5.QtWidgets.QScrollBar object at 0x7fb8e6af5ee0>, <PyQt5.QtWidgets.QComboBox object at 0x7fb8ee6ea700>, <PyQt5.QtWidgets.QListView object at 0x7fb8e6af5f70>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6ae41f0>, <PyQt5.QtWidgets.QWidget object at 0x7fb8e6afc040>, <PyQt5.QtWidgets.QMenu object at 0x7fb8e6ae48b0>]

进一步简化的最小复现代码 #

该版本代码运行后问题表现完全一致：

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import sys, os

from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *

class MainWindow(QMainWindow):

     def __init__(self, fileName=None):         
          super().__init__()
          key = QShortcut(QKeySequence("Ctrl+Q"), self)
          key.activated.connect(self.close)
          self.openFile()

    
     def openFile(self):
          fileName, _ = QFileDialog.getOpenFileName(self, 'QFileDialog.getOpenFileName()', '',
                                                    'Images (*.png *.jpeg *.jpg *.bmp *.gif *.yaml)')
          #,options=QFileDialog.DontUseNativeDialog)
                        

        
if __name__ == '__main__':
     app = QApplication(sys.argv)
     window = MainWindow()
     window.show()
     sys.exit(app.exec_())

解决方案 #

该问题属于Linux平台下原生文件对话框的已知缺陷，原生对话框关闭后会残留后台线程导致Qt事件循环无法正常退出，可选择两种方案修复：

1. 强制使用Qt自带文件对话框，避免调用系统原生对话框，修改代码如下：

fileName, _ = QFileDialog.getOpenFileName(self, 'QFileDialog.getOpenFileName()', '',
                                          'Images (*.png *.jpeg *.jpg *.bmp *.gif *.yaml)',
                                          options=QFileDialog.DontUseNativeDialog)

2. 重写主窗口的closeEvent方法，确认窗口关闭后主动终止进程：

def closeEvent(self, event):
    super().closeEvent(event)
    if event.isAccepted():
        sys.exit(0)

内容的提问来源于stack exchange，提问作者Ralf Ulrich