PyQt – 在不同线程中创建的对象的信号不起作用

Question

我在 PyQt5 和 Python 3.5 中通过运行 a Worker inside a QThread 实现多线程。在以下示例中 thread2_worker（在辅助线程内运行并）创建 thread3_worker，将 thread3_worker.finished 信号连接到 thread3_worker_finished() 并运行它。

当 thread3_worker 完成后，它会从其线程中发出 finished，但连接不起作用。我的猜测是它与不在主线程中创建或连接的 thread3_worker 有关，但我欢迎任何澄清。

import time
from PyQt5.QtCore import QObject, QThread, pyqtSignal, pyqtSlot, QCoreApplication


class Worker(QObject):
    # Generic worker.
    finished = pyqtSignal()

    def __init__(self, func):
        super().__init__()
        self.func = func

    def run(self):
        self.func()
        self.finished.emit()


def thread_factory(func):
    # Creates a Worker, a QThread and moves the Worker inside the QThread.
    worker = Worker(func)
    thread = QThread()
    worker.moveToThread(thread)
    thread.started.connect(worker.run)

    # Provision graceful termination.
    worker.finished.connect(thread.quit)
    worker.finished.connect(worker.deleteLater)
    thread.finished.connect(thread.deleteLater)

    return worker, thread


def wait():
    print("thread3:\t{}".format(QThread.currentThread()))
    time.sleep(3)


# finished signal of thread3_worker is never received.
@pyqtSlot()
def thread3_worker_finished():
    QCoreApplication.exit()


def create_thread3():
    print("thread2:\t{}".format(QThread.currentThread()))
    global thread3_worker, thread3
    # thread3_worker runs inside thread3, and all it does is call wait().
    thread3_worker, thread3 = thread_factory(wait)
    thread3_worker.finished.connect(thread3_worker_finished)  # FIXME Doesn't work.
    thread3.start()


app = QCoreApplication([])
print("Main thread:\t{}".format(QThread.currentThread()))
thread3_worker, thread3 = None, None
# thread2_worker runs inside thread2, and creates and runs thread3_worker.
thread2_worker, thread2 = thread_factory(create_thread3)
thread2.start()
app.exec_()

Answer 1

跨线程信号需要事件循环。您的 thread_factory 函数将 worker 的 finished 信号连接到其线程的 quit 插槽。 quit 插槽要求线程退出其事件循环。

所以thread3启动后，worker2结束，thread2退出。然后当 worker3 的 finished 信号发出时，不再有事件循环运行可以处理它。如果您注释掉行 worker.finished.connect(thread.quit)，您的示例应该有效。

PyQt – 在不同线程中创建的对象的信号不起作用

PyQt – Signal for object created in different thread doesn't work

python

multithreading

pyqt5

signals-slots

qthread