PyQt5 QDialog在后续线程中使用

Question

我有一个用Python 3.3写的PyQt5程序，每次按下一个按钮时，它会启动一个新的线程。这个线程会使用弹出对话框。第一次按按钮的时候一切正常，但是第二次（在第一次完成之后）程序就崩溃了。我可以在这个线程里随意调用对话框，但第二次运行线程时，程序就会卡住。下面的代码可以重现这个问题。

import sys
from threading import Thread
from PyQt5 import QtWidgets, QtCore


class Ui_Dialog(object):
    def setupUi(self, Dialog):
        Dialog.setObjectName("Dialog")
        self.pushButton = QtWidgets.QPushButton(Dialog)
        self.pushButton.setGeometry(QtCore.QRect(100, 100, 100, 50))
        self.pushButton.setObjectName("pushButton")

        self.retranslateUi(Dialog)
        QtCore.QMetaObject.connectSlotsByName(Dialog)

    def retranslateUi(self, Dialog):
        _translate = QtCore.QCoreApplication.translate
        Dialog.setWindowTitle(_translate("Dialog", "Test"))
        self.pushButton.setText(_translate("Dialog", "OK"))


class Ui_MainWindow(object):
    def setupUi(self, mainWindow):
        mainWindow.setObjectName("mainWindow")
        self.pushButton = QtWidgets.QPushButton(mainWindow)
        self.pushButton.setGeometry(QtCore.QRect(30, 20, 100, 60))
        self.pushButton.setObjectName("pushButton")

        self.retranslateUi(mainWindow)
        QtCore.QMetaObject.connectSlotsByName(mainWindow)

    def retranslateUi(self, Dialog):
        _translate = QtCore.QCoreApplication.translate
        Dialog.setWindowTitle(_translate("mainWindow", "Test"))
        self.pushButton.setText(_translate("mainWindow", "Push Me!"))


class TestDialog(QtWidgets.QDialog):
    def __init__(self, parent=None):
        super(TestDialog, self).__init__(parent)
        self.ui = Ui_Dialog()
        self.ui.setupUi(self)
        # This message simply needs to go away when the button is pushed
        self.ui.pushButton.clicked.connect(self.close)

    def show_message(self):
        super(TestDialog, self).exec_()


class Main(QtWidgets.QMainWindow):
    def __init__(self):
        super(Main, self).__init__()
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)

        self.dialog = TestDialog()

        self.ui.pushButton.clicked.connect(self.start_thread)

    def start_thread(self):
        t = Thread(target=self.show_dialog)
        t.daemon = True
        t.start()

    def show_dialog(self):
        # Do lots of background stuff here
        self.dialog.show_message()
        # The dialog can be shown multiple times within the same thread
        self.dialog.show_message()


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

如果去掉对话框的消息，程序就能正常运行。那么为什么我不能在第二个线程中调用对话框呢？我并不是想同时运行两个线程，而是一个接一个地运行。

Answer 1

感谢@Brickmastr的回答，我能够根据自己的需求稍微调整一下这个方法，适用于我不同的场景。如果有其他人也想做我正在做的事情，希望这个稍微不同的方法能帮到你。如果你在运行一个程序，想要显示一个“正在进行”的对话框，然后在处理完成后更新这个对话框，这是一种实现的方式。此外，这也是如何将同一个弹出消息用于多个耗时函数的方法。

import PyQt5

#This below import is the python file that gets created from using QtDesigner
#And running pyuic5 to create a .py file from your .ui file - hopefully
#whomever reads this is familiar with using QtDesigner
import dialogBox as fxRun

#This is the file that would contain your primary UI, also created using QtDesigner
import mainUI
import threading

class MAIN_UI(PyQt5.QtWidgets.QMainWindow, mainUI.Ui_interface):
    startSignal = PyQt5.QtCore.pyqtSignal()
    endSignal = PyQt5.QtCore.pyqtSignal()

    def __init__(self,parent=None):
        super(MAIN_UI, self).__init__(parent)
        self.setupUi(self)
        self.buttonStartFunction1.clicked.connect(self.startFunction1)
        self.buttonStartFunction2.clicked.connect(self.startFunction2)

    def startFunction1(self):
        self.startThread(self.exampleMethod1)

   def startFunction2(self):
        self.startThread(self.exampleMethod2)

    def startThread(self,functionName):
        t = threading.Thread(target=functionName)
        t.daemon = True
        t.start()

    def exampleMethod1(self):
        #This function will show the dialog box at the beginning of the process
        # and will update the text and button once the process is complete
        FULLPROGRAM.mainUI.startSignal.emit()
        #Do lots of things here that take a long time
        FULLPROGRAM.mainUI.endSignal.emit()

    def exampleMethod2(self):
        #This can be a different function, just showing that you can send
        #whatever function into the startThread() method and it will work 
        #the same way 
        FULLPROGRAM.mainUI.startSignal.emit()
        #Do lots of things here that take a long time
        FULLPROGRAM.mainUI.endSignal.emit()

class PROCESS_BOX(PyQt5.QtWidgets.QDialog, fxRun.Ui_dialogBox):
    def __init__(self,parent=None): 
        super(PROCESS_BOX,self).__init__(parent)
        self.setupUi(self)
        self.buttonProcessCompleted.clicked.connect(self.close)

    def show_dialogbox(self): 
        self.setWindowTitle("RUNNING")
        self.labelProcessStatus.setText("PROCESSING REQUEST... \n PLEASE WAIT...")
        self.buttonProcessCompleted.setEnabled(False)
        super(PROCESS_BOX,self).exec_()

    def processComplete(self): 
        self.setWindowTitle("FINISHED")
        self.labelProcessStatus.setText("PROCESS COMPLETE! \n CLICK OK")
        self.buttonProcessCompleted.setEnabled(True)    

class FULLPROGRAM: 
    def __init__(self):
        app = PyQt5.QtWidgets.QApplication(sys.argv)
        FULLPROGRAM.fxRun = PROCESS_BOX()
        FULLPROGRAM.mainUI = MAIN_UI()
        FULLPROGRAM.mainUI.startSignal.connect(FULLPROGRAM.fxRun.show_dialogbox)
        FULLPROGRAM.mainUI.endSignal.connect(FULLPROGRAM.fxRun.processComplete)
        FULLPROGRAM.mainUI.show()
        app.exec_()

def main():
    program = FULLPROGRAM()

if __name__ == '__main__':
    main()

Answer 2

我搞定了，感谢sebastian的帮助。我创建了一个信号对象，把它连接到了show_message这个函数上。我还添加了一个信号，用来告诉线程对话框已经被接受了。下面是可以正常工作的代码。

import sys
from threading import Thread
from PyQt5 import QtWidgets, QtCore


class Ui_Dialog(object):
    def setupUi(self, Dialog):
        Dialog.setObjectName("Dialog")
        self.pushButton = QtWidgets.QPushButton(Dialog)
        self.pushButton.setGeometry(QtCore.QRect(100, 100, 100, 50))
        self.pushButton.setObjectName("pushButton")

        self.retranslateUi(Dialog)
        QtCore.QMetaObject.connectSlotsByName(Dialog)

    def retranslateUi(self, Dialog):
        _translate = QtCore.QCoreApplication.translate
        Dialog.setWindowTitle(_translate("Dialog", "Test"))
        self.pushButton.setText(_translate("Dialog", "OK"))


class Ui_MainWindow(object):
    def setupUi(self, mainWindow):
        mainWindow.setObjectName("mainWindow")
        self.pushButton = QtWidgets.QPushButton(mainWindow)
        self.pushButton.setGeometry(QtCore.QRect(30, 20, 100, 60))
        self.pushButton.setObjectName("pushButton")

        self.retranslateUi(mainWindow)
        QtCore.QMetaObject.connectSlotsByName(mainWindow)

    def retranslateUi(self, Dialog):
        _translate = QtCore.QCoreApplication.translate
        Dialog.setWindowTitle(_translate("mainWindow", "Test"))
        self.pushButton.setText(_translate("mainWindow", "Push Me!"))


class TestDialog(QtWidgets.QDialog):
    signal = QtCore.pyqtSignal()

    def __init__(self, parent=None):
        super(TestDialog, self).__init__(parent)
        self.ui = Ui_Dialog()
        self.ui.setupUi(self)
        # This message simply needs to go away
        self.ui.pushButton.clicked.connect(self.close)

    def show_message(self):
        # Use this to display the pop-up so the text can be altered
        super(TestDialog, self).exec_()
        self.signal.emit()


class Main(QtWidgets.QMainWindow):
    signal = QtCore.pyqtSignal()

    def __init__(self):
        super(Main, self).__init__()
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)

        self.dialog = TestDialog()
        self.dialog_done = False

        self.ui.pushButton.clicked.connect(self.start_thread)

    def complete_dialog(self):
        self.dialog_done = True

    def wait_for_dialog(self):
        while not self.dialog_done:
            pass
        self.dialog_done = False

    def start_thread(self):
        t = Thread(target=self.show_dialog)
        t.daemon = True
        t.start()

    def show_dialog(self):
        # Do lots of background stuff here
        self.signal.emit()
        # Wait for the dialog to get closed
        self.wait_for_dialog()


if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    window = Main()
    window.show()
    dialog = TestDialog()
    window.signal.connect(dialog.show_message)
    dialog.signal.connect(window.complete_dialog)
    sys.exit(app.exec_())