wxSplitterWindow 不显示窗框

如何解决wxSplitterWindow 不显示窗框

我正在使用 wxPython 构建一个简单的应用程序，我想使用这样的布局

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这是我的示例代码

class MainWindow(wx.Frame):
    def __init__(self,title):
        super().__init__(parent=None,title=title)
        self.Maximize()
        self.initUI()

    def initUI(self):
        self.leftSplitter = wx.SplitterWindow(self,style=wx.SP_LIVE_UPDATE)
        self.leftSplitter.SetSashInvisible(False)  # not working
        self.rightSplitter = wx.SplitterWindow(self.leftSplitter,style=wx.SP_LIVE_UPDATE)
        self.rightSplitter.SetSashInvisible(False)  # not working

        self.leftPanel = wx.Panel(self.leftSplitter)
        self.rightPanel = wx.Panel(self.rightSplitter)
        self.bottomPanel = wx.Panel(self.rightSplitter)

        self.leftSizer = wx.GridSizer(10,4,3,3)
        self.rightSizer = wx.BoxSizer(wx.HORIZONTAL)
        self.bottomSizer = wx.BoxSizer(wx.HORIZONTAL)

        rightBtn = wx.Button(self.rightPanel,label="I'm on the right")
        leftBtn = wx.Button(self.leftPanel,label="I'm on the left")
        bottomBtn = wx.Button(self.bottomPanel,label="I'm on the bottom")

        self.leftSizer.Add(leftBtn)
        self.rightSizer.Add(rightBtn)
        self.bottomSizer.Add(bottomBtn)

        self.leftPanel.SetSizer(self.leftSizer)
        self.rightPanel.SetSizer(self.rightSizer)
        self.bottomPanel.SetSizer(self.bottomSizer)

        self.rightSplitter.SplitHorizontally(self.rightPanel,self.bottomPanel)
        self.rightSplitter.SetSashGravity(0.5)

        self.leftSplitter.SplitVertically(self.leftPanel,self.rightSplitter)
        self.leftSplitter.SetSashGravity(0.5)


app = wx.App()
frame = MainWindow("My Window")
frame.Show()
app.MainLoop()

当我运行它时，一切都按预期工作，除了窗扇（也称为分隔符）默认不显示。确实如果我跑

self.leftSplitter.IsSashVisible()

我猜错了。如何设置窗扇默认可见？如果使用 SetSashInvisible() 使其不可见，我如何将其重新设置为可见？