280 lines
12 KiB
Markdown
280 lines
12 KiB
Markdown
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# wxPython:了解 TreeCtrls
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> 原文：<https://www.blog.pythonlibrary.org/2017/05/16/wxpython-learning-about-treectrls/>
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wxPython GUI 工具包附带了许多小部件。一个常见的控件是树小部件。wxPython 有几个不同的树部件，包括常规的 **wx。TreeCtrl** ，更新的 **DVC_TreeCtrl** 和纯 Python 变种，**customtreecrl**和 **HyperTreeList** 。在本文中，我们将重点介绍常规的 **wx。TreeCtrl** 并学习如何创建和使用一个。
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### 创建简单的树
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创建 TreeCtrl 实际上很容易。wxPython 演示有一个相当复杂的例子，所以我不能在这里使用它。相反，我最终采用了演示示例，并尽可能多地将其剥离。结果如下:
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```py
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import wx
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class MyTree(wx.TreeCtrl):
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def __init__(self, parent, id, pos, size, style):
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wx.TreeCtrl.__init__(self, parent, id, pos, size, style)
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class TreePanel(wx.Panel):
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def __init__(self, parent):
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wx.Panel.__init__(self, parent)
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self.tree = MyTree(self, wx.ID_ANY, wx.DefaultPosition, wx.DefaultSize,
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wx.TR_HAS_BUTTONS)
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self.root = self.tree.AddRoot('Something goes here')
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self.tree.SetPyData(self.root, ('key', 'value'))
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os = self.tree.AppendItem(self.root, 'Operating Systems')
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self.tree.Expand(self.root)
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sizer = wx.BoxSizer(wx.VERTICAL)
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sizer.Add(self.tree, 0, wx.EXPAND)
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self.SetSizer(sizer)
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class MainFrame(wx.Frame):
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def __init__(self):
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wx.Frame.__init__(self, parent=None, title='TreeCtrl Demo')
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panel = TreePanel(self)
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self.Show()
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if __name__ == '__main__':
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app = wx.App(redirect=False)
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frame = MainFrame()
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app.MainLoop()
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```
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在这个例子中，我们创建了 wx 的一个子类。不做任何事情的 TreeCtrl。然后我们创建一个 panel 子类，实例化树并添加一个根和子项。最后，我们创建容纳面板的框架并运行应用程序。您最终应该会看到类似于以下内容的内容:
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这是一个相当无聊的例子，所以让我们做一些更有趣的东西。
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* * *
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### 创建 XML 查看器
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一段时间以来，我一直想用 Python 创建一个 XML 编辑器。首先，我在几个周末前写了一些代码，可以将 XML 读入 TreeCtrl 中，以便查看标记元素。对于这个例子，我将使用我在微软的 MSDN 网站上找到的一些 XML 样本:
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```py
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<book id="bk101"><author>Gambardella, Matthew</author>
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<title>XML Developer's Guide</title>
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<genre>Computer</genre>
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<price>44.95</price>
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<publish_date>2000-10-01</publish_date>
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<description>An in-depth look at creating applications
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with XML.</description></book>
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<book id="bk102"><author>Ralls, Kim</author>
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<title>Midnight Rain</title>
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<genre>Fantasy</genre>
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<price>5.95</price>
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<publish_date>2000-12-16</publish_date>
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<description>A former architect battles corporate zombies,
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an evil sorceress, and her own childhood to become queen
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of the world.</description></book>
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<book id="bk103"><author>Corets, Eva</author>
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<title>Maeve Ascendant</title>
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<genre>Fantasy</genre>
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<price>5.95</price>
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<publish_date>2000-11-17</publish_date>
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<description>After the collapse of a nanotechnology
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society in England, the young survivors lay the
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foundation for a new society.</description></book>
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<book id="bk104"><author>Corets, Eva</author>
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<title>Oberon's Legacy</title>
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<genre>Fantasy</genre>
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<price>5.95</price>
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<publish_date>2001-03-10</publish_date>
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<description>In post-apocalypse England, the mysterious
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agent known only as Oberon helps to create a new life
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for the inhabitants of London. Sequel to Maeve
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Ascendant.</description></book>
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<book id="bk105"><author>Corets, Eva</author>
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<title>The Sundered Grail</title>
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<genre>Fantasy</genre>
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<price>5.95</price>
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<publish_date>2001-09-10</publish_date>
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<description>The two daughters of Maeve, half-sisters,
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battle one another for control of England. Sequel to
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Oberon's Legacy.</description></book>
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<book id="bk106"><author>Randall, Cynthia</author>
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<title>Lover Birds</title>
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<genre>Romance</genre>
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<price>4.95</price>
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<publish_date>2000-09-02</publish_date>
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<description>When Carla meets Paul at an ornithology
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conference, tempers fly as feathers get ruffled.</description></book>
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<book id="bk107"><author>Thurman, Paula</author>
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<title>Splish Splash</title>
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<genre>Romance</genre>
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<price>4.95</price>
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<publish_date>2000-11-02</publish_date>
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<description>A deep sea diver finds true love twenty
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thousand leagues beneath the sea.</description></book>
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<book id="bk108"><author>Knorr, Stefan</author>
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<title>Creepy Crawlies</title>
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<genre>Horror</genre>
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<price>4.95</price>
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<publish_date>2000-12-06</publish_date>
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<description>An anthology of horror stories about roaches,
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centipedes, scorpions and other insects.</description></book>
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<book id="bk109"><author>Kress, Peter</author>
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<title>Paradox Lost</title>
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<genre>Science Fiction</genre>
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<price>6.95</price>
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<publish_date>2000-11-02</publish_date>
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<description>After an inadvertant trip through a Heisenberg
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Uncertainty Device, James Salway discovers the problems
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of being quantum.</description></book>
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<book id="bk110"><author>O'Brien, Tim</author>
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<title>Microsoft .NET: The Programming Bible</title>
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<genre>Computer</genre>
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<price>36.95</price>
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<publish_date>2000-12-09</publish_date>
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<description>Microsoft's .NET initiative is explored in
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detail in this deep programmer's reference.</description></book>
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<book id="bk111"><author>O'Brien, Tim</author>
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<title>MSXML3: A Comprehensive Guide</title>
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<genre>Computer</genre>
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<price>36.95</price>
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<publish_date>2000-12-01</publish_date>
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<description>The Microsoft MSXML3 parser is covered in
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detail, with attention to XML DOM interfaces, XSLT processing,
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SAX and more.</description></book>
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<book id="bk112"><author>Galos, Mike</author>
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<title>Visual Studio 7: A Comprehensive Guide</title>
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<genre>Computer</genre>
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<price>49.95</price>
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<publish_date>2001-04-16</publish_date>
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<description>Microsoft Visual Studio 7 is explored in depth,
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looking at how Visual Basic, Visual C++, C#, and ASP+ are
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integrated into a comprehensive development
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environment.</description></book>
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```
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我们需要决定的第一件事是我们想要使用什么 Python XML 解析器。我个人最喜欢 lxml，但是 Python 自己的 ElementTree 当然是一个可行的选择，而且如果你从 lxml 开始，实际上也很容易转换。但是对于这个例子，我们将使用 lxml。让我们来看看:
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```py
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import wx
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from lxml import etree, objectify
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class XmlTree(wx.TreeCtrl):
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def __init__(self, parent, id, pos, size, style):
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wx.TreeCtrl.__init__(self, parent, id, pos, size, style)
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try:
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with open(parent.xml_path) as f:
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xml = f.read()
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except IOError:
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print('Bad file')
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return
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except Exception as e:
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print('Really bad error')
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print(e)
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return
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self.xml_root = objectify.fromstring(xml)
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root = self.AddRoot(self.xml_root.tag)
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self.SetPyData(root, ('key', 'value'))
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for top_level_item in self.xml_root.getchildren():
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child = self.AppendItem(root, top_level_item.tag)
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self.SetItemHasChildren(child)
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if top_level_item.attrib:
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self.SetPyData(child, top_level_item.attrib)
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self.Expand(root)
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self.Bind(wx.EVT_TREE_ITEM_EXPANDING, self.onItemExpanding)
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def onItemExpanding(self, event):
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item = event.GetItem()
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book_id = self.GetPyData(item)
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for top_level_item in self.xml_root.getchildren():
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if top_level_item.attrib == book_id:
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book = top_level_item
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self.SetPyData(item, top_level_item)
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self.add_book_elements(item, book)
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break
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def add_book_elements(self, item, book):
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for element in book.getchildren():
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child = self.AppendItem(item, element.tag)
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if element.getchildren():
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self.SetItemHasChildren(child)
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if element.attrib:
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self.SetPyData(child, element.attrib)
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class TreePanel(wx.Panel):
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def __init__(self, parent, xml_path):
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wx.Panel.__init__(self, parent)
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self.xml_path = xml_path
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self.tree = XmlTree(self, wx.ID_ANY, wx.DefaultPosition, wx.DefaultSize,
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wx.TR_HAS_BUTTONS)
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sizer = wx.BoxSizer(wx.VERTICAL)
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sizer.Add(self.tree, 0, wx.EXPAND)
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self.SetSizer(sizer)
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class MainFrame(wx.Frame):
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def __init__(self, xml_path):
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wx.Frame.__init__(self, parent=None, title='XML Editor')
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panel = TreePanel(self, xml_path)
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self.Show()
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if __name__ == '__main__':
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xml_path = 'books.xml'
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app = wx.App(redirect=False)
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frame = MainFrame(xml_path)
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app.MainLoop()
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```
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这里的主要变化是在 TreeCtrl 子类中，尽管我们必须在其他类中做一些小的修改来传递 XML 文件路径。不过，让我们关注 TreeCtrl 类。首先，我们从文件中读取 XML，并将其加载到 lxml 的 objectify 模块中。此时，我们有了一个 XML 对象，可以用它来用数据填充 TreeCtrl。所以我们添加了根，然后遍历 XML 中的顶级子元素。对于每个顶级元素，我们向 TreeCtrl 的根添加一个项目。这是非常基本的，因为我们还应该检查每个元素，看看它是否也有子元素。我们没有。相反，我们只是假设它会调用 TreeCtrl 的 **SetItemHasChildren()** 方法。这将向元素添加一个箭头，以允许扩展元素。
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最后，我们扩展根，并将一个事件绑定到**EVT _ 树 _ 项目 _ 扩展**，这将允许我们在扩展子元素时更新它们。您可以在 **onItemExpanding** 事件处理程序和事件处理程序调用的 **add_book_elements()** 中看到这是如何完成的。在这里，我们确实使用 lxml 的 **getchildren()** 检查元素是否有子元素。如果是，那么我们调用 **SetItemHasChildren()** 。我想指出的另一件事是所有对 **SetPyData()** 的调用。SetPyData()方法用于将数据保存到树项目中。在这种情况下，我们将 XML 元素保存到树项目本身，我们可以通过 **GetPyData()** 再次访问它。如果我们想在 GUI 中添加编辑功能，这将是非常重要的。
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* * *
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### 其他零碎的东西
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wxPython 演示还展示了一些有趣的花絮。比如显示可以添加一个 **wx。ImageList** 到你的 TreeCtrl。它还显示了您可以绑定到的其他一些特定于树的事件。比如:
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* EVT _ 树 _ 项目 _ 折叠
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* EVT _ 树 _ 选择 _ 改变
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* EVT _ 树 _ 开始 _ 标签 _ 编辑
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* END _ 树 _ 结束 _ 标签 _ 编辑
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* EVT _ 树 _ 项目 _ 已激活
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当然，你也可以绑定到鼠标事件，比如 LEFT _ 左 _ 右 _ 下。
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如果您想使树元素可编辑，那么您需要传递 **wx。TR_EDIT_LABELS** 样式标志。因为我的例子只是一个查看器，所以我觉得没有必要这样做。在演示和文档中还提到了其他一些样式标志，您可能也想看看。
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* * *
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### 包扎
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在这一点上，我想你应该能够开始使用 wxPython 的便捷的 wx.TreeCtrl 了，它非常强大并且易于使用。如果您发现自己需要做一些更加定制的事情，那么我强烈建议您查看 wxPython 的一个备用树控件，比如 CustomTreeCtrl 或 HyperTreeList。
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* * *
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### 相关阅读
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* wxp 上的 wxp 文档。tree ctrl〔t1〕
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* TreeCtrl [概述](https://wxpython.org/Phoenix/docs/html/treectrl_overview.html)
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