在 QDialog reject() 上优雅地终止 QThread

Question

我有一个 QDialog，它创建一个 QThread 来做一些工作，同时保持 UI 响应，基于这里给出的结构：How To Really, Truly Use QThreads; The Full Explanation。但是，如果在线程仍在运行时调用拒绝（）（由于用户按下取消或关闭对话框），我会收到错误：

QThread：在线程仍在运行时销毁

我希望工作人员中的循环尽早中断，然后在后台进行一些清理（例如，清除一些队列，发出信号）。我已经设法用我自己的“取消”函数来做到这一点，但是我如何让它与拒绝（）（以及它可以被调用的所有多种方式）很好地配合？我不希望对话框阻止等待清理 - 它应该继续在后台运行，然后正常退出。

请参阅下面显示问题的示例代码。任何帮助将不胜感激。

#!/usr/bin/env python

from PyQt4 import QtCore, QtGui
import sys
import time

class Worker(QtCore.QObject):
    def __init__(self):
        QtCore.QObject.__init__(self)

    def process(self):
        # dummy worker process
        for n in range(0, 10):
            print 'process {}'.format(n)
            time.sleep(0.5)
        self.finished.emit()

    finished = QtCore.pyqtSignal()

class Dialog(QtGui.QDialog):
    def __init__(self):
        QtGui.QDialog.__init__(self)
        self.init_ui()

    def init_ui(self):
        self.layout = QtGui.QVBoxLayout(self)
        self.btn_run = QtGui.QPushButton('Run', self)
        self.layout.addWidget(self.btn_run)
        self.btn_cancel = QtGui.QPushButton('Cancel', self)
        self.layout.addWidget(self.btn_cancel)

        QtCore.QObject.connect(self.btn_run, QtCore.SIGNAL('clicked()'), self.run)
        QtCore.QObject.connect(self.btn_cancel, QtCore.SIGNAL('clicked()'), self.reject)

        self.show()
        self.raise_()

    def run(self):
        # start the worker thread
        self.thread = QtCore.QThread()
        self.worker = Worker()
        self.worker.moveToThread(self.thread)
        QtCore.QObject.connect(self.thread, QtCore.SIGNAL('started()'), self.worker.process)
        QtCore.QObject.connect(self.worker, QtCore.SIGNAL('finished()'), self.thread.quit)
        QtCore.QObject.connect(self.worker, QtCore.SIGNAL('finished()'), self.worker.deleteLater)
        QtCore.QObject.connect(self.thread, QtCore.SIGNAL('finished()'), self.thread.deleteLater)
        self.thread.start()

def main():
    app = QtGui.QApplication(sys.argv)
    dlg = Dialog()
    ret = dlg.exec_()

if __name__ == '__main__':
    main()

Answer 1

您的问题是：self.thread 在对话框关闭或按下取消按钮后被 Python 释放，而 Qt 线程仍在运行。

为避免这种情况，您可以指定该线程的父级。例如，

    def run(self):
        # start the worker thread
        self.thread = QtCore.QThread(self)
        self.worker = Worker()
        self.worker.moveToThread(self.thread)
        QtCore.QObject.connect(self.thread, QtCore.SIGNAL('started()'), self.worker.process)
        QtCore.QObject.connect(self.worker, QtCore.SIGNAL('finished()'), self.thread.quit)
        QtCore.QObject.connect(self.worker, QtCore.SIGNAL('finished()'), self.worker.deleteLater)
        QtCore.QObject.connect(self.thread, QtCore.SIGNAL('finished()'), self.thread.deleteLater)
        self.thread.start()

然后它将由 Qt 而不是 PyQt 拥有，因此在 Qt 优雅地终止它之前不会被 GC 收集。 实际上，这种方法只是让 Qt 不抱怨，并没有完全解决问题。

为了优雅地终止线程，常用的方法是使用一个标志来通知工作函数停止。
例如：

class Worker(QtCore.QObject):
    def __init__(self):
        QtCore.QObject.__init__(self)

    def process(self):
        # dummy worker process
        self.flag = False
        for n in range(0, 10):
            if self.flag:
                print 'stop'
                break
            print 'process {}'.format(n)
            time.sleep(0.5)
        self.finished.emit()

    finished = QtCore.pyqtSignal()

class Dialog(QtGui.QDialog):
    def __init__(self, parent=None):
        QtGui.QDialog.__init__(self, parent)
        self.init_ui()

    def init_ui(self):
        self.layout = QtGui.QVBoxLayout(self)
        self.btn_run = QtGui.QPushButton('Run', self)
        self.layout.addWidget(self.btn_run)
        self.btn_cancel = QtGui.QPushButton('Cancel', self)
        self.layout.addWidget(self.btn_cancel)

        QtCore.QObject.connect(self.btn_run, QtCore.SIGNAL('clicked()'), self.run)
        QtCore.QObject.connect(self.btn_cancel, QtCore.SIGNAL('clicked()'), self.reject)

        QtCore.QObject.connect(self, QtCore.SIGNAL('rejected()'), self.stop_worker)

        self.show()
        self.raise_()

    def stop_worker(self):
        print 'stop'
        self.worker.flag = True

    def run(self):
        # start the worker thread
        self.thread = QtCore.QThread(self)
        self.worker = Worker()
        self.worker.moveToThread(self.thread)
        QtCore.QObject.connect(self.thread, QtCore.SIGNAL('started()'), self.worker.process)
        QtCore.QObject.connect(self.worker, QtCore.SIGNAL('finished()'), self.thread.quit)
        QtCore.QObject.connect(self.worker, QtCore.SIGNAL('finished()'), self.worker.deleteLater)
        QtCore.QObject.connect(self.thread, QtCore.SIGNAL('finished()'), self.thread.deleteLater)
        self.thread.start()