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python - QSignalTransition 子类从未收到自定义 PyQt 信号

问题描述

尝试使用从为 PySide 编写的这个示例QStateMachine派生的转换来学习 PyQt5。要使用 PyQt，我只是更改了信号的定义，以及它在初始化程序中的引用方式。这是完整的代码：QSignalTransitionQSignalTransition

from PyQt5.QtCore import QObject, pyqtSignal, QSignalTransition, QCoreApplication, QStateMachine, QState, QFinalState


class Factorial(QObject):
    xChanged = pyqtSignal(int)
    def __init__(self):
        super(Factorial, self).__init__()
        self.xval = -1
        self.facval = 1
    def getX(self):
        return self.xval
    def setX(self, x):
        if self.xval == x:
            return
        self.xval = x
        self.xChanged.emit(x)
    x = property(int, getX, setX)
    def getFact(self):
        return self.facval
    def setFact(self, fac):
        self.facval = fac
    fac = property(int, getFact, setFact)

class FactorialLoopTransition(QSignalTransition):
    def __init__(self, fact):
        super(FactorialLoopTransition, self).__init__(fact.xChanged[int])
        self.fact = fact
    def eventTest(self, e):
        if not super(FactorialLoopTransition, self).eventTest(e):
            return False
        return e.arguments()[0] > 1
    def onTransition(self, e):
        x = e.arguments()[0]
        fac = self.fact.fac
        self.fact.fac = x * fac
        self.fact.x = x - 1

class FactorialDoneTransition(QSignalTransition):
    def __init__(self, fact):
        super(FactorialDoneTransition, self).__init__(fact.xChanged[int])
        self.fact = fact
    def eventTest(self, e):
        if not super(FactorialDoneTransition, self).eventTest(e):
            return False
        return e.arguments()[0] <= 1
    def onTransition(self, e):
        print(self.fact.fac)

if __name__ == '__main__':
    import sys
    app = QCoreApplication(sys.argv)
    factorial = Factorial()
    machine = QStateMachine()

    compute = QState(machine)
    compute.assignProperty(factorial, 'fac', 1)
    compute.assignProperty(factorial, 'x', 6)
    compute.addTransition(FactorialLoopTransition(factorial))

    done = QFinalState(machine)
    doneTransition = FactorialDoneTransition(factorial)
    doneTransition.setTargetState(done)
    compute.addTransition(doneTransition)

    machine.setInitialState(compute)
    machine.finished.connect(app.quit)
    machine.start()
    sys.exit(app.exec_())

这个状态机只计算 6 的阶乘并打印它。

我的问题是，在这两种转换中，这段代码： 

def eventTest(self, e):
    if not super(FactorialDoneTransition, self).eventTest(e):
        return False
    return e.arguments()[0] <= 1

False在第一次也是唯一一次调用时返回。我认为这是因为传递的事件类型不正确，并且超类返回False. 有了这种行为，转换永远不会执行，状态机保持在其初始状态。

有人可以解释是什么问题吗？我从 PySide 到 PyQt 的转换是错误的吗？

标签： pythonpython-3.xpyqtpyqt5qstatemachine

解决方案

该assignProperty()方法需要一个 Q_PROPERTY ，在 PySide/PySide2 的情况下等于 Property （这与 python 本机提供的属性不同），在 PyQt4/PyQt5 的情况下，您必须使用pyqtProperty，这就是错误的原因，所以解决方案是替换为以下内容：

from PyQt5.QtCore import QObject, pyqtSignal, QSignalTransition, QCoreApplication, QStateMachine, QState, QFinalState, pyqtProperty


class Factorial(QObject):
    xChanged = pyqtSignal(int)
    def __init__(self):
        super(Factorial, self).__init__()
        self.xval = -1
        self.facval = 1

    def getX(self):
        return self.xval

    def setX(self, x):
        if self.xval == x:
            return
        self.xval = x
        self.xChanged.emit(x)

    x = pyqtProperty(int, getX, setX) # <---

    def getFact(self):
        return self.facval

    def setFact(self, fac):
        self.facval = fac

    fac = pyqtProperty(int, getFact, setFact) # <---

# ...

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