PyQt5 QThread不起作用，GUI仍然冻结。

Question

我有这段代码（如果你安装了pyqt5，你应该能够自己运行它）：

import sys
import time

from PyQt5.QtWidgets import QApplication, QPushButton, QVBoxLayout, QWidget
from PyQt5.QtCore import QObject, QThread, pyqtSignal, pyqtSlot


class Worker(QObject):
    def __init__(self):
        super().__init__()
        self.thread = None


class Tab(QObject):
    def __init__(self, _main):
        super().__init__()
        self._main = _main


class WorkerOne(Worker):
    finished = pyqtSignal()

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

    @pyqtSlot(str)
    def print_name(self, name):
        for _ in range(100):
            print("Hello there, {0}!".format(name))
            time.sleep(1)

        self.finished.emit()
        self.thread.quit()


class SomeTabController(Tab):
    def __init__(self, _main):
        super().__init__(_main)
        self.threads = {}

        self._main.button_start_thread.clicked.connect(self.start_thread)

        # Workers
        self.worker1 = WorkerOne()
        #self.worker2 = WorkerTwo()
        #self.worker3 = WorkerThree()
        #self.worker4 = WorkerFour()

    def _threaded_call(self, worker, fn, *args, signals=None, slots=None):
        thread = QThread()
        thread.setObjectName('thread_' + worker.__class__.__name__)

        # store because garbage collection
        self.threads[worker] = thread

        # give worker thread so it can be quit()
        worker.thread = thread

        # objects stay on threads after thread.quit()
        # need to move back to main thread to recycle the same Worker.
        # Error is thrown about Worker having thread (0x0) if you don't do this
        worker.moveToThread(QThread.currentThread())

        # move to newly created thread
        worker.moveToThread(thread)

        # Can now apply cross-thread signals/slots

        #worker.signals.connect(self.slots)
        if signals:
            for signal, slot in signals.items():
                try:
                    signal.disconnect()
                except TypeError:  # Signal has no slots to disconnect
                    pass
                signal.connect(slot)

        #self.signals.connect(worker.slots)
        if slots:
            for slot, signal in slots.items():
                try:
                    signal.disconnect()
                except TypeError:  # Signal has no slots to disconnect
                    pass
                signal.connect(slot)

        thread.started.connect(lambda: fn(*args)) # fn needs to be slot
        thread.start()

    @pyqtSlot()
    def _receive_signal(self):
        print("Signal received.")

    @pyqtSlot(bool)
    def start_thread(self):
        name = "Bob"
        signals = {self.worker1.finished: self._receive_signal}
        self._threaded_call(self.worker1, self.worker1.print_name, name,
                            signals=signals)


class MainWindow(QWidget):
    def __init__(self):
        super().__init__()

        self.setWindowTitle("Thread Example")
        form_layout = QVBoxLayout()
        self.setLayout(form_layout)
        self.resize(400, 400)

        self.button_start_thread = QPushButton()
        self.button_start_thread.setText("Start thread.")
        form_layout.addWidget(self.button_start_thread)

        self.controller = SomeTabController(self)


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

    _main = MainWindow()
    _main.show()

    sys.exit(app.exec_())

然而，WorkerOne 仍然阻塞了我的 GUI 线程，当 WorkerOne.print_name 正在运行时窗口无响应。

最近我一直在研究 QThreads，但根据我所做的研究，我不确定为什么这不起作用。

怎么回事？

- James Lemieux

Answer 1

这个问题是由连接lambda方法引起的，因为这个lambda不属于Worker，所以它不会在新线程上运行。解决方法是使用functools.partial：

from functools import partial
...
thread.started.connect(partial(fn, *args))

完整代码：

完整的代码：

import sys
import time

from functools import partial

from PyQt5.QtWidgets import QApplication, QPushButton, QVBoxLayout, QWidget
from PyQt5.QtCore import QObject, QThread, pyqtSignal, pyqtSlot


class Worker(QObject):
    def __init__(self):
        super().__init__()
        self.thread = None


class Tab(QObject):
    def __init__(self, _main):
        super().__init__()
        self._main = _main


class WorkerOne(Worker):
    finished = pyqtSignal()

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

    @pyqtSlot(str)
    def print_name(self, name):
        for _ in range(100):
            print("Hello there, {0}!".format(name))
            time.sleep(1)

        self.finished.emit()
        self.thread.quit()


class SomeTabController(Tab):
    def __init__(self, _main):
        super().__init__(_main)
        self.threads = {}

        self._main.button_start_thread.clicked.connect(self.start_thread)

        # Workers
        self.worker1 = WorkerOne()
        #self.worker2 = WorkerTwo()
        #self.worker3 = WorkerThree()
        #self.worker4 = WorkerFour()

    def _threaded_call(self, worker, fn, *args, signals=None, slots=None):
        thread = QThread()
        thread.setObjectName('thread_' + worker.__class__.__name__)

        # store because garbage collection
        self.threads[worker] = thread

        # give worker thread so it can be quit()
        worker.thread = thread

        # objects stay on threads after thread.quit()
        # need to move back to main thread to recycle the same Worker.
        # Error is thrown about Worker having thread (0x0) if you don't do this
        worker.moveToThread(QThread.currentThread())

        # move to newly created thread
        worker.moveToThread(thread)

        # Can now apply cross-thread signals/slots

        #worker.signals.connect(self.slots)
        if signals:
            for signal, slot in signals.items():
                try:
                    signal.disconnect()
                except TypeError:  # Signal has no slots to disconnect
                    pass
                signal.connect(slot)

        #self.signals.connect(worker.slots)
        if slots:
            for slot, signal in slots.items():
                try:
                    signal.disconnect()
                except TypeError:  # Signal has no slots to disconnect
                    pass
                signal.connect(slot)

        thread.started.connect(partial(fn, *args)) # fn needs to be slot
        thread.start()

    @pyqtSlot()
    def _receive_signal(self):
        print("Signal received.")

    @pyqtSlot(bool)
    def start_thread(self):
        name = "Bob"
        signals = {self.worker1.finished: self._receive_signal}
        self._threaded_call(self.worker1, self.worker1.print_name, name,
                            signals=signals)


class MainWindow(QWidget):
    def __init__(self):
        super().__init__()

        self.setWindowTitle("Thread Example")
        form_layout = QVBoxLayout()
        self.setLayout(form_layout)
        self.resize(400, 400)

        self.button_start_thread = QPushButton()
        self.button_start_thread.setText("Start thread.")
        form_layout.addWidget(self.button_start_thread)

        self.controller = SomeTabController(self)


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

    _main = MainWindow()
    _main.show()

    sys.exit(app.exec_())

- eyllanesc

---

哇，那是我最后一个会去找的地方。非常感谢你！ - James Lemieux

@eyllanesc 这似乎与我几年前在一个问题中提供的答案相矛盾。你知道我错过了什么吗（为什么在这里使用partial有效而在其他问题中无效）？ - three_pineapples

@three_pineapples的partial并没有创建一个函数，它只是扩展了你可以在文档中看到的源代码中的参数。你从哪里得到的partial会创建一个新的方法？ - eyllanesc

我不确定，因为我回答那个问题已经有一段时间了。我觉得我的答案是错误的，但它解决了问题。我想我会尝试重新审视它，并看看我哪里出错了。 - three_pineapples

Answer 2

为了避免幻灯片功能显示图像时阻塞 GUI，我运行了以下简单代码。

一个后台线程类等待一秒钟，然后向等待的 GUI 发出信号已完成。

class Waiter(QThread):
    result = pyqtSignal(object)

    def __init__(self):
        QtCore.QThread.__init__(self)

    def run(self):
        while self.isRunning:
            self.sleep(1)
            self.result.emit("waited for 1s")

然后在主窗口中，将幻灯片的开始和停止按钮连接到主应用程序的开始和停止方法，并将nextImage函数连接到Waiter线程发出的信号。

    self.actionstopSlideShow.triggered.connect(self.stopSlideShow)
    self.actionslideShowStart.triggered.connect(self.startSlideShow)
    self.waitthread = Waiter()
    self.waitthread.result.connect(self.nextImage)

然后主应用程序有两种方法可以启动和停止时间计时器。

def startSlideShow(self):
    """Start background thread that waits one second,
    on wait result trigger next image
    use thread otherwise gui freezes and stop button cannot be pressed
    """
    self.waitthread.start()

def stopSlideShow(self):
    self.waitthread.terminate()
    self.waitthread.wait()

到目前为止，我在PyQt5中从QThread进行子类化没有遇到任何问题，GUI更改都在主（GUI）线程内处理。

- knobi

---

您能详细阐述这个答案与我的问题的相关性吗？ - James Lemieux

我的建议是使用QThread作为基类，然后使用self.sleep()而不是time.sleep()，并使用主线程执行.terminate()和.wait()来停止工作线程。 - knobi