Qt on Python 中的 QThread

Posted 2023-02-16

【中文标题】Qt on Python 中的 QThread

【英文标题】：QThread in Qt on Python

【发布时间】：2019-06-20 23:36:07

【问题描述】：

在阅读了关于如何使用 QThread 的扩展讨论后，​​我使用 QThread 使用工作对象，并通过子类化覆盖它的 run 方法不是正确的方法。但是，在我打算使用的方法中，我需要传递一个额外的函数参数，该参数在启动线程并使用moveToThread 将工作线程推送到线程时不可用。此信息（参数）在按下按钮时可用，并传达有关要移动的对象的信息。

在我的代码的完整版本中，三个独立的控制器分别用于三个独立的对象，您可以在下面找到一个最小的工作示例，演示我试图传递参数的内容。该代码也可在pastebin 上获得，感兴趣的行号是 10-28、46-50 和 133-135。

到目前为止，我已经尝试在连接到 worker 中的实际函数的行中使用 lambda 构造函数。那是self.thread.started.connect(self.obj.moveLeftIncrement) 的行，然后尝试使用slots，但我不太了解它们。此外，尽管使用 QThread，有时 GUI 会挂起，并且程序退出后会出现错误，其中之一如下：

进程以退出代码 -1073740791 (0xC0000409) 结束

我的问题如下：

如何在运行时传递参数和/或使用槽？ 如何防止退出时出现程序错误？ 为什么在这种情况下子类化 QThread 直接起作用，虽然不推荐？

---

from PySide2.QtCore import *
from PySide2.QtWidgets import *
from PySide2.QtGui import *
import sys
import time

class Worker(QObject):
    finished = Signal(int)

    @Slot(str)
    def moveLeftIncrement(self, controller_name):
        # controller_name = "Controller 1"
        print("Controller name is ", controller_name)
        if controller_name == "Controller 1":
            print("Starting controller 1")
            time.sleep(2)
            print("Finishing sleep")
        elif controller_name == "Controller 2":
            print("Starting controller 2")
            time.sleep(2)
            print("Finishing sleep")
        elif controller_name == "Controller 3":
            print("Starting controller 3")
            time.sleep(2)
            print("Finishing sleep")
        else:
            raise Exception("No such controller found!")
        self.finished.emit(0)


class Window(QWidget):
    """ Inherits from QWidget """
    def closeEvent(self, *args, **kwargs):
        print("\nClosing")

    def __init__(self):
        super().__init__()
        self.CONTINUOUS_MOVE_SWITCH = False
        self.title = 'Control Controllers'
        self.left = 10
        self.top = 10
        self.width = 320
        self.height = 100
        self.AxesMapping = [0, 1, 2, 3]
        self.initUI()
        self.thread = QThread()
        self.obj = Worker()
        self.obj.moveToThread(self.thread)
        self.thread.started.connect(self.obj.moveLeftIncrement)
        self.obj.finished.connect(self.thread.quit)

    def initUI(self):
        """ Initializes the GUI either using the grid layout or the absolute position layout"""
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)
        Comp1 = self.createGridLayout("Controller 2")
        windowLayout = QGridLayout()

        windowLayout.addWidget(Comp1, 0, 0)
        self.setLayout(windowLayout)
        self.show()

    def createGridLayout(self, controller):
        """Creates a grid layout for the buttons"""
        box_size = QSize(640, 440)
        HGroupBox = QGroupBox(controller)
        layout = QGridLayout()
        layout.addWidget(self.createButton("left", controller), 2, 1)
        layout.addWidget(self.createButton("right", controller), 2, 3)
        layout.addWidget(self.createButton("forward", controller), 1, 2)
        layout.addWidget(self.createButton("backward", controller), 3, 2)
        HGroupBox.setLayout(layout)
        HGroupBox.setFixedSize(box_size)
        return HGroupBox

    def createButton(self, name, controller):
        """Creates a button with the specified size"""
        button_size = QSize(100, 40)
        icon_size = 40
        button = QPushButton()
        button.Name = name
        button.Controller = controller
        button.Moving = 0
        button.clicked.connect(lambda: self.buttonPresssed(button))
        button.setFixedSize(button_size)
        return button

    def moveLeftIncrement(self, controller, button):
        if controller == "Controller 1":
            time.sleep(2)
        elif controller == "Controller 2":
            time.sleep(2)
        elif controller == "Controller 3":
            time.sleep(2)
        else:
            raise Exception("No such controller found!")

    def moveRightIncrement(self, controller, button):
        if controller == "Controller 1":
            time.sleep(2)
        elif controller == "Controller 2":
            time.sleep(2)
        elif controller == "Controller 3":
            time.sleep(2)
        else:
            raise Exception("No such controller found!")

    def moveForwardIncrement(self, controller, button):
        if controller == "Controller 1":
            time.sleep(2)
        elif controller == "Controller 2":
            time.sleep(2)
        elif controller == "Controller 3":
            time.sleep(2)
        else:
            raise Exception("No such controller found!")

    def moveBackwardIncrement(self, controller, button):
        if controller == "Controller 1":
            time.sleep(2)
        elif controller == "Controller 2":
            time.sleep(2)
        elif controller == "Controller 3":
            time.sleep(2)
        else:
            raise Exception("No such controller found!")

    def buttonPresssed(self, button):
        name = button.Name
        if hasattr(button, 'Controller'):
            controller = button.Controller
            print("The controller selected is", controller)
        if name == 'left':
            self.thread.start()
        elif name == 'right':
            print("Moved controller right for a single step")
            self.moveRightIncrement(controller, button)
        elif name == 'forward':
            self.moveForwardIncrement(controller, button)
            print("Moved controller forward for a single step")
        elif name == 'backward':
            self.moveBackwardIncrement(controller, button)
            print("Moved controller backward for a single step")
        elif name == "up":
            print("Moving controller up for a single step")
            self.moveUpIncrement(controller, button)
        elif name == "down":
            print("Moving controller down for a single step")
            self.moveDownIncrement(controller, button)


if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = Window()
    sys.exit(app.exec_())

【参考方案1】：

- 如何在运行时传递参数和/或使用槽？

如果你想调用另一个线程中的对象的槽，你必须使用信号，因为它是线程安全的。

- 如何防止退出时出现程序错误？

在你的情况下，错误是因为你有一个线程正在运行而你没有停止它，一个可能的选择是使用 closeEvent 来停止它。

- 为什么不推荐子类化 QThread 在这种情况下直接起作用？

不是不推荐，而是非常有限，有更好的选择，比如使用一个存在于另一个线程中的工作线程，这样我们就可以有不同的方法，而不仅仅是在 run 方法中执行任务。还可以通过 worker 选项让多个对象存在于一个线程中。

---

在工人的情况下，方法如下：

创建一个 QThread 并启动处理的线程。 创建一个将存在于另一个线程中并移动另一个线程的对象 连接调用对象槽的信号，也连接将发送对象信息到 GUI 的信号。 发出他们将在必要时调用的信号。

综合以上，解决办法是：

from PySide2 import QtCore, QtGui, QtWidgets
import time

class Worker(QtCore.QObject):
    error = QtCore.Signal()

    @QtCore.Slot(str)
    def moveLeftIncrement(self, controller):
        if controller == "Controller 1":
            time.sleep(2)
        elif controller == "Controller 2":
            time.sleep(2)
        elif controller == "Controller 3":
            time.sleep(2)
        else:
            self.error.emit("No such controller found!")

    @QtCore.Slot(str)
    def moveRightIncrement(self, controller):
        if controller == "Controller 1":
            time.sleep(2)
        elif controller == "Controller 2":
            time.sleep(2)
        elif controller == "Controller 3":
            time.sleep(2)
        else:
            self.error.emit("No such controller found!")

    @QtCore.Slot(str)
    def moveForwardIncrement(self, controller, button):
        if controller == "Controller 1":
            time.sleep(2)
        elif controller == "Controller 2":
            time.sleep(2)
        elif controller == "Controller 3":
            time.sleep(2)
        else:
            self.error.emit("No such controller found!")

    @QtCore.Slot(str)
    def moveBackwardIncrement(self, controller, button):
        if controller == "Controller 1":
            time.sleep(2)
        elif controller == "Controller 2":
            time.sleep(2)
        elif controller == "Controller 3":
            time.sleep(2)
        else:
            self.error.emit("No such controller found!")

class Window(QtWidgets.QWidget):
    leftClicked = QtCore.Signal(str)
    rightClicked = QtCore.Signal(str)
    forwardClicked = QtCore.Signal(str)
    backwardClicked = QtCore.Signal(str)

    def __init__(self):
        super().__init__()
        self.CONTINUOUS_MOVE_SWITCH = False
        self.title = 'Control Controllers'
        self.left, self.top, self.width, self.height = 10, 10, 320, 100
        self.AxesMapping = [0, 1, 2, 3]

        self.initUI()

        self.thread = QtCore.QThread(self)
        self.thread.start()
        self.obj = Worker()
        self.obj.moveToThread(self.thread)
        self.leftClicked.connect(self.obj.moveLeftIncrement)
        self.rightClicked.connect(self.obj.moveRightIncrement)
        self.forwardClicked.connect(self.obj.moveForwardIncrement)
        self.backwardClicked.connect(self.obj.moveBackwardIncrement)
        self.obj.error.connect(self.on_error)

    def initUI(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)
        Comp1 = self.createGridLayout("Controller 2")
        windowLayout = QtWidgets.QGridLayout(self)
        windowLayout.addWidget(Comp1, 0, 0)

    def createGridLayout(self, controller):
        """Creates a grid layout for the buttons"""
        box_size = QtCore.QSize(640, 440)
        HGroupBox = QtWidgets.QGroupBox(controller)
        layout = QtWidgets.QGridLayout()
        layout.addWidget(self.createButton("left", controller), 2, 1)
        layout.addWidget(self.createButton("right", controller), 2, 3)
        layout.addWidget(self.createButton("forward", controller), 1, 2)
        layout.addWidget(self.createButton("backward", controller), 3, 2)
        HGroupBox.setLayout(layout)
        HGroupBox.setFixedSize(box_size)
        return HGroupBox

    def createButton(self, name, controller):
        button_size = QtCore.QSize(100, 40)
        icon_size = 40
        button = QtWidgets.QPushButton()
        button.Name = name
        button.Controller = controller
        button.Moving = 0
        button.clicked.connect(self.buttonPresssed)
        button.setFixedSize(button_size)
        return button

    @QtCore.Slot()
    def buttonPresssed(self):
        button = self.sender()
        name = button.Name
        if hasattr(button, 'Controller'):
            controller = button.Controller
            print("The controller selected is", controller)
            if name == 'left':
                self.leftClicked.emit(controller)
            elif name == 'right':
                print("Moved controller right for a single step")
                self.rightClicked.emit(controller)
            elif name == 'forward':
                print("Moved controller forward for a single step")
                self.forwardClicked.emit(controller)
            elif name == 'backward':
                print("Moved controller backward for a single step")
                self.backwardClicked.emit(controller)

    @QtCore.Slot(str)
    def on_error(self, error):
        print(error)

    def closeEvent(self, event):
        self.thread.quit()
        self.thread.wait()
        super(Window, self).closeEvent(event)

if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    ex = Window()
    ex.show()
    sys.exit(app.exec_())

【讨论】：

感谢您的及时和简洁的回复。我对 Qt 中的信号/插槽感到非常困惑。我今天将在完整的代码中尝试它。顺便说一句，是否可以在QtCore.Slot 中使用自定义类？假设我有一个名为 Controller 的类，我可以执行以下操作吗？ @QtCore.Slot(Controller) def moveForwardIncrement(self, Controller): controller = Controller.name if controller == "Controller 1": time.sleep(2) elif controller == "Controller 2": time.sleep(2) self.error.emit("没有找到这样的控制器！")