How to stop a QThread from the GUI

Question

This is a follow up question to a previous one I posted earlier. The problem is how to stop (terminate|quit|exit) a QThread from the GUI when using the recommended method

Answer 1

I know its long ago but i just stumbled over the same problem.

I have been also searching for an appropriate way to do this. Finally it was easy. When exiting the application the task needs to be stopped and the thread needs to be stopped calling its quit method. See stop_thread method on bottom. And you need to wait for the thread to finish. Otherwise you will get QThread: Destroyed while thread is still running' message at exit.

(I also changed my code to use pyside)

import time, sys
from PySide.QtCore  import *
from PySide.QtGui import *

class Worker(QObject):
    'Object managing the simulation'

    stepIncreased = Signal(int)

    def __init__(self):
        super(Worker, self).__init__()
        self._step = 0
        self._isRunning = True
        self._maxSteps = 20

    def task(self):
        if not self._isRunning:
            self._isRunning = True
            self._step = 0

        while self._step  < self._maxSteps  and self._isRunning == True:
            self._step += 1
            self.stepIncreased.emit(self._step)
            time.sleep(0.1)

        print "finished..."

    def stop(self):
        self._isRunning = False


class SimulationUi(QDialog):
    def __init__(self):
        super(SimulationUi, self).__init__()

        self.btnStart = QPushButton('Start')
        self.btnStop = QPushButton('Stop')
        self.currentStep = QSpinBox()

        self.layout = QHBoxLayout()
        self.layout.addWidget(self.btnStart)
        self.layout.addWidget(self.btnStop)
        self.layout.addWidget(self.currentStep)
        self.setLayout(self.layout)

        self.thread = QThread()
        self.thread.start()

        self.worker = Worker()
        self.worker.moveToThread(self.thread)
        self.worker.stepIncreased.connect(self.currentStep.setValue)

        self.btnStop.clicked.connect(lambda: self.worker.stop())
        self.btnStart.clicked.connect(self.worker.task)

        self.finished.connect(self.stop_thread)

    def stop_thread(self):
        self.worker.stop()
        self.thread.quit()
        self.thread.wait()

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