wxPython的isChecked()响应不一致-为何如此？

Question

我有一个图表，当用户右键点击时会出现一个弹出菜单。默认情况下，子选项A是选中的。我希望用户能够切换这个选中状态，以便实现不同的功能。因此，我想知道A是否已经被选中，并且希望这个检查状态的处理放在一个单独的函数里。我们把创建菜单的函数叫做showPopupMenu()，需要知道A的选中状态的函数叫做commandA()。

现在，如果我默认选中A并打印出A的IsChecked()状态，在showPopupMenu()中这个值是True，而在commandA()中这个值是False。如果默认情况下A没有被选中，那么结果就反过来了——showPopupMenu()显示的选中状态是False，而commandA()显示的是True。这让人觉得在commandA()中的IsChecked()状态只是showPopupMenu()中IsChecked()状态的反向结果。为什么会这样呢？

import wxversion
wxversion.ensureMinimal('2.8')
from numpy import arange, sin, pi
import matplotlib
matplotlib.use('WX')
from matplotlib.backends.backend_wxagg import FigureCanvasWxAgg as FigureCanvas
from matplotlib.backends.backend_wx import NavigationToolbar2Wx
from matplotlib.figure import Figure
import wx


class MyForm(wx.Frame):

    def __init__(self):
        wx.Frame.__init__(self,None,-1,
                     'Example Frame',size=(550,350))

        self.SetBackgroundColour(wx.NamedColor("WHITE"))

        self.figure = Figure()
        self.axes = self.figure.add_subplot(111)
        t = arange(0.0,3.0,0.01)
        s = sin(2*pi*t)

        self.axes.plot(t,s)
        self.canvas = FigureCanvas(self, -1, self.figure)
        self.canvas.Bind(wx.EVT_RIGHT_DOWN,
                   self.showPopupMenu)

        self.sizer = wx.BoxSizer(wx.VERTICAL)
        self.sizer.Add(self.canvas, 1, wx.LEFT | wx.TOP | wx.GROW)
        self.SetSizer(self.sizer)
        self.Fit()

    def showPopupMenu(self, event):
        if not hasattr(self, "popupTwo"):
            self.popupOne = wx.NewId()
            self.popupTwo = wx.NewId()
            self.popupThree = wx.NewId()
            self.popupA = wx.NewId()
            self.popupB = wx.NewId()

    self.popupOne = wx.Menu()
    my_a = self.popupOne.Append(self.popupA, "A", kind=wx.ITEM_CHECK)
    self.popupOne.Append(self.popupB, "B")
    self.popupOne.Check(self.popupA, True)
    #self.popupOne.Check(self.popupA, False)
    print "in showPopupMenu(): ",self.popupOne.IsChecked(self.popupA)
        self.Bind(wx.EVT_MENU, self.commandA, my_a) 

        menu = wx.Menu()
        menu.AppendMenu(-1, 'One', self.popupOne)
        menu.Append(self.popupTwo, "Two")
        menu.Append(self.popupThree, "Three")

        self.PopupMenu(menu)
        menu.Destroy()

    def commandA(self, event):
    print "in commandA(): ", self.popupOne.IsChecked(self.popupA)

# Run the program
if __name__ == "__main__":
    app = wx.PySimpleApp()
    frame = MyForm().Show()
    app.MainLoop()

这个脚本的输出：

在showPopupMenu()中：True

在commandA()中：False

Answer 1

当你点击A的时候，勾选标记会从“真”变成“假”，所以你在那看到的输出是“假”。不过，你每次都在创建和销毁你的窗口，这就是为什么你从来没有看到勾选状态的变化。

下面是一个例子，教你怎么设置菜单，而不需要每次都创建和销毁它：

import wx
import gui

class MainFrame(wx.Frame):
    def __init__( self, parent ):
        wx.Frame.__init__ (self, parent)

        # Layout my frame
        sizer = wx.BoxSizer(wx.VERTICAL)
        self.panel = wx.Panel(self)
        self.panel.Layout()
        self.panel.Bind(wx.EVT_RIGHT_DOWN, self.showPopupMenu)
        sizer.Add( self.panel, 1, wx.EXPAND |wx.ALL, 0 )
        self.SetSizer( sizer )
        self.Layout()

        # Add the menu
        self.popupA = wx.NewId()
        self.popupOne = wx.Menu()

        my_a = self.popupOne.Append(self.popupA, "A", kind=wx.ITEM_CHECK)
        self.popupOne.Check(self.popupA, True)

        self.Bind(wx.EVT_MENU, self.commandA, my_a)

        self.menu = wx.Menu()
        self.menu.AppendMenu(-1, 'One', self.popupOne)

    def showPopupMenu(self, event):
        print "in showPopupMenu(): ",self.popupOne.IsChecked(self.popupA)
        self.PopupMenu(self.menu)

    def commandA(self, event):
        event.Skip()
        print "in commandA(): ", self.popupOne.IsChecked(self.popupA)

class app(wx.App):
    def OnInit(self):
        self.m_frame = MainFrame(None)
        self.m_frame.Show()
        self.SetTopWindow(self.m_frame)
        return True

app = app(0)
app.MainLoop()