python - 如何从 GUI 停止 QThread

Question

这是我之前发布的上一个问题的后续问题。问题是如何在使用不继承 Qthread 的推荐方法，而是创建 QObject 然后将其移动到 QThread 时从 GUI 停止（终止|退出|退出）QThread。下面是一个工作示例。我可以启动 GUI 和 Qthread，我可以让后者更新 GUI。但是，我无法阻止它。我为 qthread 尝试了几种方法（quit()、exit() 甚至 terminate()），但均无济于事。非常感谢帮助。

这是完整的代码：

import time, sys
from PyQt4.QtCore  import *
from PyQt4.QtGui import * 

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

    stepIncreased = pyqtSignal(int, name = 'stepIncreased')
    def __init__(self):
        super(SimulRunner, self).__init__()
        self._step = 0
        self._isRunning = True
        self._maxSteps = 20

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

    def stop(self):
        self._isRunning = False

class SimulationUi(QDialog):
    'PyQt interface'

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

        self.goButton = QPushButton('Go')
        self.stopButton = QPushButton('Stop')
        self.currentStep = QSpinBox()

        self.layout = QHBoxLayout()
        self.layout.addWidget(self.goButton)
        self.layout.addWidget(self.stopButton)
        self.layout.addWidget(self.currentStep)
        self.setLayout(self.layout)

        self.simulRunner = SimulRunner()
        self.simulThread = QThread()
        self.simulRunner.moveToThread(self.simulThread)
        self.simulRunner.stepIncreased.connect(self.currentStep.setValue)


        self.stopButton.clicked.connect(simulThread.qui)  # also tried exit() and terminate()
        # also tried the following (didn't work)
        # self.stopButton.clicked.connect(self.simulRunner.stop)
        self.goButton.clicked.connect(self.simulThread.start)
        self.simulThread.started.connect(self.simulRunner.longRunning)
        self.simulRunner.stepIncreased.connect(self.current.step.setValue)


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

Answer 1

我知道它很久以前，但我只是偶然发现了同样的问题。

我也一直在寻找合适的方法来做到这一点。最后很容易。退出应用程序时，需要停止任务，并且需要停止调用其退出方法的线程。请参阅底部的 stop_thread 方法。你需要等待线程完成。否则，您将在退出时收到 QThread: Destroyed while thread is still running' 消息。

（我还更改了我的代码以使用 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_())

Answer 2

I found out that my original question was actually two questions in one: in order to stop a secondary thread from the main one, you need two things:

1. Be able to communicate from the main thread down to the secondary thread

2. Send the proper signal to stop the thread

I haven't been able to solve (2), but I figured out how to solve (1), which gave me a workaround to my original problem. Instead of stopping the thread, I can stop the thread's processing (the longRunning() method)

The problem is that a a secondary thread can only respond to signals if it runs its own event loop. A regular Qthread (which is what my code used) does not. It is easy enough, though, to subclass QThread to that effect:

class MyThread(QThread):
    def run(self):
        self.exec_()

and used self.simulThread = MyThread() in my code instead of the original self.simulThread = Qthread(). This ensures that the secondary thread runs an event loop. That was not enough, though. The longRunning() method needs to have a chance to actually process the event coming down from the main thread. With the help of this SO answer I figured out that the simple addition of a QApplication.processEvent() in the longRunning() method gave the secondary thread such a chance. I can now stop the processing carried out in the secondary thread, even though I haven't figured out how to stop the thread itself.

To wrap up. My longRunning method now looks like this:

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

and my GUI thread has these three lines that do the job (in addition to the QThread subclass listed above):

    self.simulThread = MyThread()
    self.simulRunner.moveToThread(self.simulThread)
    self.stopButton.clicked.connect(self.simulRunner.stop)

Comments are welcome!

Answer 3

您可以通过调用 exit() 或 quit() 来停止线程。在极端情况下，您可能希望强制终止（）正在执行的线程。然而，这样做是危险的和不鼓励的。有关详细信息，请阅读 terminate() 和 setTerminationEnabled() 的文档。

源代码：https ://doc.qt.io/qtforpython/PySide2/QtCore/QThread.html