Odtnhj

This is PyQt5 code. I want to count down 5 seconds and update every 1 second. Then application will pop up QMessageBox.
But it will closed after click button on QMessageBox due to QObject::setParent: Cannot set parent, new parent is in a different thread,
detail code below:

from PyQt5 import QtCore, QtGui, QtWidgets
import sys, time
from _thread import *

class ThreadClass(QtCore.QThread):
 # Create the signal
 sig = QtCore.pyqtSignal(int)

 def __init__(self, mw, parent=None):
 self.mw = mw
 self.mbox = QtWidgets.QMessageBox()
 super().__init__(parent)
 self.sig.connect(self.showtime)

 def showtime(self, t):
 self.mw.label.setText(str(t))

 def run(self):
 for t in range(5):
 self.sig.emit(t)
 time.sleep(1)
 self.mbox.about(QtWidgets.QMainWindow(), "Title", "Finished")

class Ui_MainWindow(object):
 def setupUi(self, MainWindow):
 MainWindow.setObjectName("MainWindow")
 MainWindow.resize(253, 181)
 self.centralwidget = QtWidgets.QWidget(MainWindow)
 self.centralwidget.setObjectName("centralwidget")
 self.pushButton = QtWidgets.QPushButton(self.centralwidget)
 self.pushButton.setGeometry(QtCore.QRect(90, 100, 75, 23))
 self.pushButton.setObjectName("pushButton")
 self.label = QtWidgets.QLabel(self.centralwidget)
 self.label.setGeometry(QtCore.QRect(20, 20, 211, 16))
 self.label.setObjectName("label")
 self.tc = ThreadClass(self)
 self.pushButton.clicked.connect(lambda: self.tc.start())
 #self.pushButton.clicked.connect(lambda: start_new_thread(showtime, (self.label, )))
 MainWindow.setCentralWidget(self.centralwidget)


 QtCore.QMetaObject.connectSlotsByName(MainWindow)
 self.pushButton.setText("Show")
 self.label.setText("Time") 

if __name__ == '__main__':
 app = QtWidgets.QApplication(sys.argv)
 ex = Ui_MainWindow()
 w = QtWidgets.QMainWindow()
 ex.setupUi(w)
 w.show()
 sys.exit(app.exec_())

App will close after clicked button on QMessageBox and error message below.

QBasicTimer::stop: Failed. Possibly trying to stop from a different thread
QBasicTimer::stop: Failed. Possibly trying to stop from a different thread
QBasicTimer::stop: Failed. Possibly trying to stop from a different thread
QBasicTimer::stop: Failed. Possibly trying to stop from a different thread
QObject::setParent: Cannot set parent, new parent is in a different thread
QObject::setParent: Cannot set parent, new parent is in a different thread

Try it:

import sys #, time
from PyQt5 import QtCore, QtGui, QtWidgets
from _thread import *

class ThreadClass(QtCore.QThread):
 # Create the signal
 sig = QtCore.pyqtSignal(int)
 finish = QtCore.pyqtSignal() # +++

 def __init__(self, mw, parent=None):
# self.mw = mw
# self.mbox = QtWidgets.QMessageBox()
 super().__init__(parent)
# self.sig.connect(self.showtime)

# def showtime(self, t):
# self.mw.label.setText(str(t))

 def run(self):
 for t in range(5):
 self.sig.emit(t)
 #time.sleep(1)
 QtCore.QThread.msleep(1000)

 self.finish.emit() # +++
# self.mbox.about(QtWidgets.QMainWindow(), "Title", "Finished")

class Ui_MainWindow(object):
 def setupUi(self, MainWindow):
 MainWindow.setObjectName("MainWindow")
 MainWindow.resize(253, 181)
 self.centralwidget = QtWidgets.QWidget(MainWindow)
 self.centralwidget.setObjectName("centralwidget")

 self.pushButton = QtWidgets.QPushButton(self.centralwidget)
 self.pushButton.setGeometry(QtCore.QRect(90, 100, 75, 23))
 self.pushButton.setObjectName("pushButton")

 self.label = QtWidgets.QLabel(self.centralwidget)
 self.label.setGeometry(QtCore.QRect(20, 20, 211, 16))
 self.label.setObjectName("label")

 self.tc = ThreadClass(self)
 self.pushButton.clicked.connect(lambda: self.tc.start())
 #self.pushButton.clicked.connect(lambda: start_new_thread(showtime, (self.label, )))

 self.tc.sig.connect(self.showtime) # +++
 self.tc.finish.connect(self.finishTime) # +++


 MainWindow.setCentralWidget(self.centralwidget)


 QtCore.QMetaObject.connectSlotsByName(MainWindow)
 self.pushButton.setText("Show")
 self.label.setText("Time") 

# +++
 def showtime(self, t):
 self.label.setText(str(t)) 

# +++
 def finishTime(self):
 self.mbox = QtWidgets.QMessageBox()
 self.mbox.about(QtWidgets.QMainWindow(), "Title", "Finished")


if __name__ == '__main__':
 app = QtWidgets.QApplication(sys.argv)
 w = QtWidgets.QMainWindow()
 ex = Ui_MainWindow()
 ex.setupUi(w)
 w.show()
 sys.exit(app.exec_())