PyQt |信号不在 QThread 中处理，而是在主线程中处理

在这个简单的 PyQt 演示程序中，我从主线程发出信号。在工作线程中，我连接到它们，但信号处理程序在主线程中运行：

from PyQt4 import QtGui, QtCore
import threading
from time import sleep
import sys


class Data():
    def __init__(self, a, b):
        self.a = a
        self.b = b

    def __str__(self):
        return "Data having %d and %d" % (self.a, self.b)

class Worker(QtCore.QThread):
    def __init__(self, parent):
        QtCore.QThread.__init__(self)
        self.p = parent

    def run(self):
        self.connect(self.p, QtCore.SIGNAL("newTask"), self.task)
        print "[%s] running exec_()" % threading.currentThread()
        self.exec_()

    def task(self, dataobj):
        print "[%s] Processing" % threading.currentThread(), dataobj
        sleep(3)
        print "Done with", dataobj
        self.emit(QtCore.SIGNAL("taskDone"), str(dataobj))

class App(QtCore.QObject):
    def __init__(self):
        QtCore.QObject.__init__(self)
        self.w = Worker(self)
        self.connect(self.w, QtCore.SIGNAL("taskDone"), self.on_task_done)
        self.w.start()

    def assign_tasks(self):
        self.emit(QtCore.SIGNAL("newTask"), Data(3, 4))
        self.emit(QtCore.SIGNAL("newTask"), Data(5, 6))
        print "[%s] Tasks sent" % threading.currentThread()

    @staticmethod
    def on_task_done(objstr):
        print "[%s] App: Worker finished with" % threading.currentThread(), objstr

if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    a = App()
    sleep(1)
    a.assign_tasks()
    sleep(20)
    sys.exit(app.exec_())

但结果显示回调是在主线程中运行的：

[<_DummyThread(Dummy-1, started daemon 105564)>] running exec_()
[<_MainThread(MainThread, started 105612)>] Processing Data having 3 and 4
Done with Data having 3 and 4
[<_MainThread(MainThread, started 105612)>] App: Worker finished with Data having 3 and 4
[<_MainThread(MainThread, started 105612)>] Processing Data having 5 and 6
Done with Data having 5 and 6
[<_MainThread(MainThread, started 105612)>] App: Worker finished with Data having 5 and 6
[<_MainThread(MainThread, started 105612)>] Tasks sent

我究竟做错了什么？不幸的是，PyQt 文档对此非常不完整且相互矛盾。

如果我使用，我会得到类似的结果moveToThread技术：

from PyQt4 import QtGui, QtCore
import threading
from time import sleep
import sys

class Data():
    def __init__(self, a, b):
        self.a = a
        self.b = b

    def __str__(self):
        return "Data having %d and %d" % (self.a, self.b)

class Worker(QtCore.QObject):
    def __init__(self, parent):
        QtCore.QObject.__init__(self)
        self.connect(parent, QtCore.SIGNAL("newTask"), self.task)

    def task(self, dataobj):
        print "[%s] Processing" % threading.currentThread(), dataobj
        sleep(3)
        print "Done with", dataobj
        self.emit(QtCore.SIGNAL("taskDone"), str(dataobj))

    def start(self):
        print "[%s] start()" % threading.currentThread()

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

        self.w = Worker(self)
        self.t = QtCore.QThread(self)
        self.w.moveToThread(self.t)
        self.connect(self.w, QtCore.SIGNAL("taskDone"), self.on_task_done)
        self.connect(self.t, QtCore.SIGNAL("started()"), self.w.start)
        self.t.start()

    def assign_tasks(self):
        self.emit(QtCore.SIGNAL("newTask"), Data(3, 4))
        self.emit(QtCore.SIGNAL("newTask"), Data(5, 6))
        print "[%s] Tasks sent" % threading.currentThread()

    @staticmethod
    def on_task_done(objstr):
        print "[%s] App: Worker finished with" % threading.currentThread(), objstr

if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    a = App()
    sleep(1)
    a.assign_tasks()
    sleep(20)
    sys.exit(app.exec_())

结果是：

[<_DummyThread(Dummy-1, started daemon 108992)>] start()
[<_MainThread(MainThread, started 107004)>] Processing Data having 3 and 4
Done with Data having 3 and 4
[<_MainThread(MainThread, started 107004)>] App: Worker finished with Data having 3 and 4
[<_MainThread(MainThread, started 107004)>] Processing Data having 5 and 6
Done with Data having 5 and 6
[<_MainThread(MainThread, started 107004)>] App: Worker finished with Data having 5 and 6
[<_MainThread(MainThread, started 107004)>] Tasks sent

Your Worker对象“活动”在主线程中，这意味着它们的所有信号将由主线程的事件循环处理。事实上，这些物体是QThreads 并没有改变这一点。

如果您希望信号由不同的线程处理，您首先需要使用它的方法将工作对象移动到该线程moveToThread http://pyqt.sourceforge.net/Docs/PyQt4/qobject.html#moveToThread method.

所以在你的情况下，只有run方法实际上是在不同的线程中执行的，task方法仍然在主线程中执行。改变这种情况的一种方法是：

• 做你的Worker一个常规的QObject, not a QThread
• 创建一个QThread在你的App，启动它并将工作线程移至该线程
• 然后向工作进程发送信号，使其开始处理

您应该查看这些参考资料：

• QObject线程亲和性 http://qt-project.org/doc/qt-5/qobject.html#thread-affinity
• Qt 线程基础知识 http://qt-project.org/doc/qt-5/thread-basics.html
• Qt 中的多线程技术 http://qt-project.org/doc/qt-5/threads-technologies.html

edit:

我在您的代码中注意到的其他一些事情：

• 你正在混合 python 线程和 qt 线程。threading.currentThread will not正确反映当前的qt线程。使用QThread.currentThread()为了那个原因。
• 装饰你正在调用的插槽pyqtSlots，不这样做可能会导致此类问题。
• use 新风格信号 http://pyqt.sourceforge.net/Docs/PyQt4/new_style_signals_slots.html。 PyQt5 不再支持旧样式信号，新样式信号使用起来更容易、更好。

因此，这是您应该可以使用的代码版本：

from PyQt4 import QtGui, QtCore
import threading
from time import sleep
import sys

class Data():
    def __init__(self, a, b):
        self.a = a
        self.b = b

    def __str__(self):
        return "Data having %d and %d" % (self.a, self.b)

class Worker(QtCore.QObject):

    taskDone = QtCore.pyqtSignal(str)

    def __init__(self, parent):
        QtCore.QObject.__init__(self)
        parent.newTask.connect(self.task)

    @QtCore.pyqtSlot(object)
    def task(self, dataobj):
        print "[%s] Processing" % QtCore.QThread.currentThread().objectName(), dataobj
        sleep(3)
        print "Done with", dataobj
        self.taskDone.emit(str(dataobj))

    @QtCore.pyqtSlot()
    def start(self):
        print "[%s] start()" % QtCore.QThread.currentThread().objectName()

class App(QtCore.QObject):

    newTask = QtCore.pyqtSignal(object)

    def __init__(self):
        QtCore.QObject.__init__(self)
        self.w = Worker(self)
        self.t = QtCore.QThread(self, objectName='workerThread')
        self.w.moveToThread(self.t)
        self.w.taskDone.connect(self.on_task_done)
        self.t.started.connect(self.w.start)
        self.t.start()

    def assign_tasks(self):
        self.newTask.emit(Data(3, 4))
        self.newTask.emit(Data(5, 6))
        print "[%s] Tasks sent" % QtCore.QThread.currentThread().objectName()

    @staticmethod
    def on_task_done(objstr):
        print "[%s] App: Worker finished with" % QtCore.QThread.currentThread().objectName(), objstr

if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    QtCore.QThread.currentThread().setObjectName('main')
    a = App()
    sleep(1)
    a.assign_tasks()
    from utils import sigint
    sys.exit(app.exec_())

我已经设置了线程objectNames 使输出更具可读性：

[workerThread] start()
[main] Tasks sent
[workerThread] Processing Data having 3 and 4
Done with Data having 3 and 4
[workerThread] Processing Data having 5 and 6
[main] App: Worker finished with Data having 3 and 4
Done with Data having 5 and 6
[main] App: Worker finished with Data having 5 and 6