PyQt：如何将停止信号发送到对象正在运行有条件的 while 循环的线程？

Question

我正在做一些多线程。我有一个带有work方法的工作类，我将其发送到单独的QThread. 该work方法内部有一个有条件的 while 循环。我希望能够向工作对象发送信号以停止它（将_running条件更改为 false）。这将导致 while 循环退出，并从工作对象（连接到工作线程的退出槽）发送完成信号。

false 条件通过信号发送到工作对象，但从未收到，我认为这是因为 while 循环阻止了其线程的事件循环。即使我放入QCoreApplication.processEvents()while 循环，也没有任何反应。问题出在哪儿？为什么不处理信号？（请注意，Worker 上停止槽中的打印语句从未执行过 - 但奇怪的是，线程似乎以错误的方式停止）。

这是代码：

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

class Worker(QObject):
    sgnFinished = pyqtSignal()

    def __init__(self, parent):
        QObject.__init__(self, parent)

        self._running = True

    @pyqtSlot()
    def stop():
        print 'stop signal received, switching while loop condition to false'
        self._running = False

    @pyqtSlot()    
    def work(self):
        while self._running:                 #this blocks the thread, if changed to an if clause, thread finishes as expected!
            QCoreApplication.processEvents() #this doesn't help!
            time.sleep(0.1)
            print 'doing work...'

        #do some cleanup here, then signal the worker is done
        self.sgnFinished.emit()


class Client(QObject):
    sgnStop = pyqtSignal()

    def __init__(self, parent):
        QObject.__init__(self, parent)

        self._thread = None
        self._worker = None

    def toggle(self, enable):
        if enable:
            if not self._thread:
                self._thread = QThread()

            self._worker = Worker(None)
            self._worker.moveToThread(self._thread)

            self._worker.sgnFinished.connect(self.on_worker_done)
            self.sgnStop.connect(self._worker.stop)

            self._thread.started.connect(self._worker.work)
            self._thread.start()
        else:
            print 'sending stop signal to the worker object'
            self.sgnStop.emit() #send a queuedconnection type signal to the worker, because its in another thread

    @pyqtSlot() 
    def on_worker_done(self):
        print 'workers job was interrupted manually'
        self._thread.quit()
        #self._thread.wait() not sure this is neccessary

if __name__ == '__main__':
    app = QCoreApplication(sys.argv)

    client = Client(None)
    client.toggle(True)
    raw_input('Press something')
    client.toggle(False)

Answer 1

您的示例中有两个主要问题：

首先，您发出一个信号来停止工作线程，但由于该信号是跨线程的，因此它将被发布到接收者的事件队列中。但是，工作线程正在运行阻塞 while 循环，因此无法处理挂起的事件。有几种方法可以解决这个问题，但最简单的可能是直接调用工作人员的stop方法而不是使用信号。

其次，您没有在主线程中显式运行事件循环，因此从工作线程发送的跨线程信号无法排队。但更重要的是，在用户按下按键后也没有任何东西可以阻止程序退出 - 因此客户端和工作线程将立即被垃圾收集。

下面是您的示例的重写版本，它修复了所有问题：

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

class Worker(QObject):
    sgnFinished = pyqtSignal()

    def __init__(self, parent):
        QObject.__init__(self, parent)
        self._mutex = QMutex()
        self._running = True

    @pyqtSlot()
    def stop(self):
        print 'switching while loop condition to false'
        self._mutex.lock()
        self._running = False
        self._mutex.unlock()

    def running(self):
        try:
            self._mutex.lock()
            return self._running
        finally:
            self._mutex.unlock()

    @pyqtSlot()
    def work(self):
        while self.running():
            time.sleep(0.1)
            print 'doing work...'
        self.sgnFinished.emit()

class Client(QObject):
    def __init__(self, parent):
        QObject.__init__(self, parent)
        self._thread = None
        self._worker = None

    def toggle(self, enable):
        if enable:
            if not self._thread:
                self._thread = QThread()

            self._worker = Worker(None)
            self._worker.moveToThread(self._thread)
            self._worker.sgnFinished.connect(self.on_worker_done)

            self._thread.started.connect(self._worker.work)
            self._thread.start()
        else:
            print 'stopping the worker object'
            self._worker.stop()

    @pyqtSlot()
    def on_worker_done(self):
        print 'workers job was interrupted manually'
        self._thread.quit()
        self._thread.wait()
        if raw_input('\nquit application [Yn]? ') != 'n':
            qApp.quit()

if __name__ == '__main__':

    # prevent some harmless Qt warnings
    pyqtRemoveInputHook()

    app = QCoreApplication(sys.argv)

    client = Client(None)

    def start():
        client.toggle(True)
        raw_input('Press something\n')
        client.toggle(False)

    QTimer.singleShot(10, start)

    sys.exit(app.exec_())