Python PyQt Widget connect() 和 disconnect()
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PyQt Widget connect() and disconnect()
提问by alphanumeric
Depending on a conditions I would like to connect/re-connect a button to a different function.
根据条件，我想将按钮连接/重新连接到不同的功能。
Let's say I have a button:
假设我有一个按钮：
myButton = QtGui.QPushButton()
For this example let's say I check if there is an internet connection.
对于这个例子，假设我检查是否有互联网连接。
if connected == True:
myButton.clicked.connect(function_A)
elif connected == False:
myButton.clicked.connect(function_B)
First of all I would like to disconnect a button from any function it was already connected before the button is being re-assigned/re-connected to another function (function_A or function_B). Secondly, I have already noticed that after the button is re-connected it takes an extra click for the button to pick up a new function. After the button is re-connected to another function it still attempts to run a previous function - a function to which a button was connected earlier (before a re-connection). Please advice. Thanks in advance!
首先，在按钮被重新分配/重新连接到另一个功能（function_A 或 function_B）之前，我想将按钮与它已经连接的任何功能断开连接。其次，我已经注意到，重新连接按钮后，需要额外单击按钮才能选择新功能。按钮重新连接到另一个功能后，它仍会尝试运行前一个功能 - 按钮先前（重新连接之前）连接到的功能。请指教。提前致谢！
EDITED LATER:
稍后编辑：
It appears a widget's .disconnect()method can be used to disconnect a button from a function it it is connected.
看起来小部件的.disconnect()方法可用于断开按钮与其连接的功能的连接。
myButton.disconnect()
Unfortunately .disconnect() throws an error if a widget is not connected to any function. To get around it I am using Try/Except. But I would rather use a more elegant solution...
不幸的是，如果小部件未连接到任何函数， .disconnect() 会引发错误。为了解决这个问题，我使用了 Try/Except。但我宁愿使用更优雅的解决方案......
try: myButton.clicked.disconnect()
except Exception: pass
采纳答案by ekhumoro
If you need to reconnect signals in many places, then you could define a generic utility function like this:
如果您需要在许多地方重新连接信号，那么您可以定义一个通用的实用函数，如下所示：
def reconnect(signal, newhandler=None, oldhandler=None):
while True:
try:
if oldhandler is not None:
signal.disconnect(oldhandler)
else:
signal.disconnect()
except TypeError:
break
if newhandler is not None:
signal.connect(newhandler)
...
if connected:
reconnect(myButton.clicked, function_A)
else:
reconnect(myButton.clicked, function_B)
(NB: the loop is needed for safely disconnecting a specific handler, because it may have been connected multple times, and disconnectonly removes one connection at a time.).
（注意：安全断开特定处理程序需要循环，因为它可能已连接多次，并且一次disconnect仅删除一个连接。）。
回答by Alvaro Fuentes
Try this:
尝试这个：
from PyQt4 import QtGui as gui
app = gui.QApplication([])
myButton = gui.QPushButton()
def function_A():
myButton.clicked.disconnect() #this disconnect all!
myButton.clicked.connect(function_B)
print 'function_A'
def function_B():
myButton.clicked.disconnect(function_B) #this disconnect function_B
myButton.clicked.connect(function_A)
print 'function_B'
myButton.clicked.connect(function_A)
myButton.setText("Click me!")
myButton.show()
app.exec_()
