发出 `Signal` 直接使 `QStateMachine` 转换到另一个 `QState`

Question

我有一个状态机，如下图所示：

我在Python中实现了这个状态机，使用的是标准的状态模式。这个状态机在一个与PySide6应用程序主线程不同的线程中运行。我们把这个状态机的类叫做Controller。

在图形用户界面（GUI）方面，我使用的是Qt for Python 状态机框架。（注意：链接的文档是针对PySide2/PySide5的，但我使用的是PySide6。出于某种原因，PySide6没有相应的文档。）这样可以很方便地定义当进入某个状态时，GUI会发生什么。

我想要的不是让GUI来发起状态转换，而是让我的核心状态机Controller在另一个线程中控制这些转换。通常情况下，人们会使用<QState>.addTransition(...)在GUI层面添加转换，但我希望GUI只是向Controller发送命令，然后当Controller转换状态时，我希望它能发出一个Signal，触发PySide6的QStateMachine进入某个特定状态，从而设置该状态下所有合适的属性。换句话说，我希望GUI能够向Controller状态机发送命令，并且GUI能够“监听”Controller的状态转换。

所以问题是，给定一个QState，我该如何向它发送信号，以强制它所属的QStateMachine转换到那个状态？还是说我需要向QStateMachine发送信号，并提供一个QState来进行转换？

示例程序：

from __future__ import annotations
from abc import ABC, abstractmethod
from typing import override
from PySide6.QtStateMachine import QState


class Controller:
    def __init__(self, initial_state: IState, states: list[QState]) -> None:
        """Initialize the controller to the given initial state and call the `
        on_entry` method for the state.
        """
        self.__state = initial_state
        self.__state.controller = self
        self.__state.on_entry()
        self.__state.states = states

    def _transition_to(self, new_state: IState) -> None:
        """Transition from the current state to the given new state. This calls
        the `on_exit` method on the current state and the `on_entry` of the
        new state. This method should not be called by any object other than
        concrete implementations of `IState`.
        """
        self.__state.on_exit()
        self.__state = new_state
        self.__state.controller = self
        self.__state.on_entry()

    @property
    def state(self):
        """Get the current state"""
        return self.__state

    def start_camera_exposure(self) -> None:
        self.__state.start_camera_exposure()

    def stop_camera_exposure(self) -> None:
        self.__state.stop_camera_exposure()

    def abort_camera_exposure(self) -> None:
        self.__state.abort_camera_exposure()


class IState(ABC):
    """Serve as an interface between the controller and the explicit, individual states."""

    @property
    def controller(self) -> Controller:
        return self.__controller

    @controller.setter
    def controller(self, controller: Controller) -> None:
        self.__controller = controller

    @property
    def states(self) -> list[QState]:
        return self.__states

    @states.setter
    def states(self, states: list[QState]):
        self.__states = states

    def on_entry(self) -> None:
        """Can be overridden by a state to perform an action when the state is
        being entered, i.e., transitions into. It is not required to be overridden.
        """
        pass

    def on_exit(self) -> None:
        """Can be overridden by a state to perform an action when the state is
        being exited, i.e., transitioned from. It is not required to be overridden.
        """
        pass

    # If a concrete implementation does not handle the called method, i.e., it is an invalid action
    # in the specific state, it is enough to simply call `pass`.

    @abstractmethod
    def start_camera_exposure(self) -> None: ...

    @abstractmethod
    def stop_camera_exposure(self) -> None: ...

    @abstractmethod
    def abort_camera_exposure(self) -> None: ...


class Idle(IState):
    @override
    def on_entry(self):
        # I want to emit a signal here to force a `QStateMachine` to go to state: `self.__states[0]`
        print("Idling ...")

    def start_camera_exposure(self) -> None:
        self.controller._transition_to(CameraExposing())

    def stop_camera_exposure(self) -> None:
        pass

    def abort_camera_exposure(self) -> None:
        pass


class CameraExposing(IState):
    @override
    def on_entry(self) -> None:
        # I want to emit a signal here to force a `QStateMachine` to go to state: `self.__states[1]`
        print("Starting camera exposure ...")

    @override
    def on_exit(self) -> None:
        print("Stopping camera exposure ...")

    def start_camera_exposure(self) -> None:
        pass

    def stop_camera_exposure(self) -> None:
        self.controller._transition_to(SavingCameraImages())

    def abort_camera_exposure(self) -> None:
        self.controller._transition_to(AbortingCameraExposure())


class SavingCameraImages(IState):
    @override
    def on_entry(self) -> None:
        # I want to emit a signal here to force a `QStateMachine` to go to state: `self.__states[2]`
        print("Saving camera images ...")
        self.controller._transition_to(Idle())

    def start_camera_exposure(self) -> None:
        pass

    def stop_camera_exposure(self) -> None:
        pass

    def abort_camera_exposure(self) -> None:
        pass


class AbortingCameraExposure(IState):
    @override
    def on_entry(self) -> None:
        # I want to emit a signal here to force a `QStateMachine` to go to state: `self.__states[3]`
        print("Aborting camera exposure ...")
        self.controller._transition_to(Idle())

    def start_camera_exposure(self) -> None:
        pass

    def stop_camera_exposure(self) -> None:
        pass

    def abort_camera_exposure(self) -> None:
        pass

在GUI方面，我有类似这样的代码：

from PySide6.QtStateMachine import QState, QStateMachine


class MainWindow(QWidget):
    def __init__(self) -> None:
        super().__init__()

        self.machine = QStateMachine(parent=self)
        self.state_idle = QState(self.machine)
        self.state_camera_exposing = QState(self.machine)
        self.state_saving_camera_images = QState(self.machine)
        self.state_aborting_camera_exposure = QState(self.machine)
        self.machine.setInitialState(self.state_idle)
        self.states = [
            self.state_idle,
            self.state_camera_exposing,
            self.state_saving_camera_images,
            self.state_aborting_camera_exposure,
        ]

        self.initialize()

图形用户界面线程状态转换状态机信号 pyside6 qt 状态模式

发出 `Signal` 直接使 `QStateMachine` 转换到另一个 `QState`

1 个回答

撰写回答