Question

我正在尝试使用后端上的Python，前端上的QML和用于创建状态机的scxml编写桌面应用程序。我正在使用PySide2。我的意图是通过状态机描述应用程序的逻辑。基于状态，QML中的UI应该做出相应的反应。另外，后端应根据输入的状态等执行方法。

我的项目由3个文件组成：具有后端逻辑的main.py，具有UI的ui.qml，具有状态机的stateMachine.scxml。

main.py的内容：

from PySide2.QtScxml import QScxmlStateMachine
from PySide2.QtWidgets import QApplication
from PySide2.QtCore import QUrl, QObject, Slot
from PySide2.QtQml import QQmlApplicationEngine


class BackEnd(QObject):
    def __init__(self):
        super().__init__()

    @Slot()
    def ev_slot(self):
        '''method called on event t1'''
        print('event t1')

    @Slot(bool)
    def st_slot(self, active):
        '''method called on entering and exiting state s2'''
        if active:
            print('s2 entered')
        else:
            print('s2 exited')


app = QApplication([])
qml_url = QUrl("ui.qml")

engine = QQmlApplicationEngine()

# loading state machine
my_state_machine = QScxmlStateMachine.fromFile('stateMachine.scxml')

backend = BackEnd()

# registering state machine in QML context
engine.rootContext().setContextProperty("stateMachine", my_state_machine)
# connecting event of state machine to method of backend
conn1 = my_state_machine.connectToEvent("t1", backend, "aev_slot()")
# connecting state of state machine to method of backend
conn2 = my_state_machine.connectToState("s2", backend, "ast_slot(bool)")

my_state_machine.start()

engine.load(qml_url)

app.exec_()

UI非常简单：它仅包含3个向状态机（ui.qml文件）提交事件的按钮：

import QtQuick 2.0
import QtQuick.Controls 2.2


ApplicationWindow {
    width: column.width
    height: column.height
    visible: true

    Column {
        id: column
        spacing: 10
        Button {
            id: button0
            text: qsTr("t1")
            onClicked: stateMachine.submitEvent('t1')
        }

        Button {
            id: button1
            text: qsTr("t2")
            onClicked: stateMachine.submitEvent('t2')
        }

        Button {
            id: button2
            text: qsTr("t3")
            onClicked: stateMachine.submitEvent('t3')
        }
    }

}

状态机stateMachine.scxml包含3个状态：s1，s2，s3和过渡t1，t2，{{1} }：

t3

这里的问题是一切正常。第<?xml version="1.0" encoding="UTF-8"?> <scxml xmlns="http://www.w3.org/2005/07/scxml" version="1.0" binding="early" xmlns:qt="http://www.qt.io/2015/02/scxml-ext" name="stateMachine" initial="s1"> <state id="s1"> <transition type="external" event="t1" target="s2"/> <onentry> <log label="entered" expr="s1"/> </onentry> </state> <state id="s2"> <transition type="external" event="t2" target="s3"/> <onentry> <log label="entered" expr="s2"/> </onentry> </state> <state id="s3"> <transition type="external" event="t3" target="s1"> </transition> <onentry> <log label="entered" expr="s3"/> </onentry> </state> </scxml>行有一个错误：方法名是my_state_machine.connectToEvent("t1", backend, "aev_slot()")，而不是ev_slot()。但是，如果我将其更改为专有名称，则会出现以下错误：

aev_slot()

以某种方式，方法名称中的第一个字母将被忽略。难道我做错了什么？我对Qt和PySide2非常陌生。总体来说这是一个好方法吗？我正在使用PySide2 5.11.1a1.dev1530708810518

Answer 1

您必须使用SLOT()以字符串形式传递方法（请注意，SLOT与Slot装饰器不同）。

from PySide2 import QtCore, QtGui, QtQml, QtScxml


class BackEnd(QtCore.QObject):
    @QtCore.Slot()
    def ev_slot(self):
        '''method called on event t1'''
        print('event t1')

    @QtCore.Slot(bool)
    def st_slot(self, active):
        '''method called on entering and exiting state s2'''
        if active:
            print('s2 entered')
        else:
            print('s2 exited')


if __name__ == '__main__':
    import sys
    app = QtGui.QGuiApplication(sys.argv)
    qml_url = QtCore.QUrl.fromLocalFile("ui.qml")

    # loading state machine
    my_state_machine = QtScxml.QScxmlStateMachine.fromFile('stateMachine.scxml')

    backend = BackEnd()
    conn1 = my_state_machine.connectToEvent("t1", backend, QtCore.SLOT("ev_slot()"))
    conn2 = my_state_machine.connectToState("s2", backend, QtCore.SLOT("st_slot(bool)"))
    my_state_machine.start()

    engine = QtQml.QQmlApplicationEngine()
    engine.rootContext().setContextProperty("stateMachine", my_state_machine)
    engine.load(qml_url)

    if not engine.rootObjects():
        sys.exit(-1)

    sys.exit(app.exec_())

SLOT仅在插槽名称前添加1，SIGNAL与2相同，因此，如果您不想仅使用前缀1：{{1 }}，（我不建议您这样做，因为它会使代码的可读性降低）

PySide2中的QScxmlStateMachine.connectToEvent的怪异行为

1 个答案: