信号和插槽：当简单示例不起作用时

Question

有两个小部件：按钮和标签。 按下按钮时，我想运行标签的myFunction（）方法。 如何使用信号和插槽实现这一目标？以下示例不起作用。

from PyQt import QtCore, QtGui

class label(QtGui.QLabel):
    def __init__(self, parent=None):
        super(label, self).__init__(parent) 
        self.show()

    def myFunction(self, arg=None):
        print '...myFunction: received arg =', arg

class button(QtGui.QPushButton):
    def __init__(self, parent=None):
        super(button, self).__init__(parent) 
        self.clicked.connect(self.click)
        self.show()

    def click(self):
        print 'emitted'
        self.emit(QtCore.SIGNAL('buttonClicked'))


lbl = label()
btn = button()

Answer 1

方法1

一种解决方案是使用全局声明的QObject变量connector。我们使用connector.signal：发出信号并连接要在signal.emit（）上执行的方法。

从第一个小部件发出：connector.signal.emit()

连接第二个小部件的方法：connector.signal.connect(self.myFunction)

from PySide import QtCore, QtGui

class Communicate(QtCore.QObject):
    signal = QtCore.Signal(str)

connector=Communicate()

class label(QtGui.QLabel):
    def __init__(self, parent=None):
        super(label, self).__init__(parent) 
        connector.signal.connect(self.labelFunction)
        self.show()

    def labelFunction(self, arg=None):
        print '...labelFunction: arg =', arg

class button(QtGui.QPushButton):
    def __init__(self, parent=None):
        super(button, self).__init__(parent) 
        self.clicked.connect(self.click)
        self.show()

    def click(self):
        connector.signal.emit("Hello World")

lbl = label()
btn = button()

方法2

我们可以通过传递label.labelFunction作为回调参数来实现相同的功能。按钮的connector将连接到它：

from PySide import QtCore, QtGui

class Communicate(QtCore.QObject):
    signal = QtCore.Signal(str)

class label(QtGui.QLabel):
    def __init__(self, parent=None):
        super(label, self).__init__(parent) 
        self.show()

    def labelFunction(self, arg=None):
        print '...labelFunction: arg = %s'%arg

class button(QtGui.QPushButton):
    def __init__(self, callback=None, parent=None):
        super(button, self).__init__(parent) 
        self.callback=callback
        self.clicked.connect(self.click)
        self.show()

    def click(self):
        connector=Communicate()
        connector.signal.connect(self.callback)
        connector.signal.emit("Hello World")

lbl = label()
btn = button(callback=lbl.labelFunction)

方法3

就像之前我们仍然在button.clicked上发出一样。 但是使用不同的语法将label连接到customSignal： self.connect(btn, QtCore.SIGNAL('customSignal'), Function)

from PySide import QtCore, QtGui

def Function(arg=None):
    print 'Function.arg: %r'%arg

class button(QtGui.QPushButton):
    def __init__(self, parent=None):
        super(button, self).__init__(parent) 
        self.clicked.connect(self.click)
        self.show()

    def click(self):
        self.emit(QtCore.SIGNAL('customSignal'), 'String Arument')

btn = button()

class label(QtGui.QLabel):
    def __init__(self, parent=None):
        super(label, self).__init__(parent) 
        self.connect(btn, QtCore.SIGNAL('customSignal'), Function) 
        self.show()   

lbl = label()