wxPython - wx.TreeCtrl 中的 GetFirstVisibleItem() 方法

在本文中，我们将讨论与 wxPython 的 wx.TreeCtrl 类关联的 GetFirstVisibleItem()函数。让我们看看它的用途和用途：

Syntax: wx.TreeCtrl.GetFirstVisibleItemId(self)

Parameters:

No parameters are required by GetFirstVisibleItemId() method.

Returns:

wx.TreeItemId object that is the first visible item of the tree

其实现如下：

以下示例打印第一个可见项是否有效。我们将使用与 wx.TreeItemId 对象 IsOk() 方法关联的 IsOk() 方法执行此操作，如果树项是有效项，则该方法返回 true。

示例 1：

Python

import wx
  
  
class MyTree(wx.TreeCtrl):
  
    def __init__(self, parent, id, pos, size, style):
        wx.TreeCtrl.__init__(self, parent, id, pos, size, style)
  
  
class TreePanel(wx.Panel):
  
    def __init__(self, parent):
        wx.Panel.__init__(self, parent)
          
        # create tree control in window
        self.tree = MyTree(self, wx.ID_ANY, wx.DefaultPosition, wx.DefaultSize,
                           wx.TR_HAS_BUTTONS)
  
        # CREATE TREE ROOT
        self.root = self.tree.AddRoot('root')
        self.tree.SetPyData(self.root, ('key', 'value'))
  
        # add item to root
        item = self.tree.AppendItem(self.root, "Item")
        item2 = self.tree.AppendItem(self.root, "Item")
  
        # print if first visible item is a valid tree item
        if(self.tree.GetFirstVisibleItem().IsOk()):
            print("Is Valid Item")
        else:
            print("Invalid Tree Item")
  
        sizer = wx.BoxSizer(wx.VERTICAL)
        sizer.Add(self.tree, 100, wx.EXPAND)
        self.SetSizer(sizer)
  
  
class MainFrame(wx.Frame):
  
    def __init__(self):
        wx.Frame.__init__(self, parent=None, title='TreeCtrl Demo')
        panel = TreePanel(self)
        self.Show()
  
  
if __name__ == '__main__':
    app = wx.App(redirect=False)
    frame = MainFrame()
    app.MainLoop()

输出：

Is Valid Item

示例 2：

Python

import wx
  
  
class MyTree(wx.TreeCtrl):
  
    def __init__(self, parent, id, pos, size, style):
        wx.TreeCtrl.__init__(self, parent, id, pos, size, style)
  
  
class TreePanel(wx.Panel):
  
    def __init__(self, parent):
        wx.Panel.__init__(self, parent)
          
        # create tree control in window
        self.tree = MyTree(self, wx.ID_ANY, wx.DefaultPosition, wx.DefaultSize,
                           wx.TR_HAS_BUTTONS)
  
        # print if first visible item is a valid tree item
        if(self.tree.GetFirstVisibleItem().IsOk()):
            print("Is Valid Item")
        else:
            print("Invalid Tree Item")
  
        sizer = wx.BoxSizer(wx.VERTICAL)
        sizer.Add(self.tree, 100, wx.EXPAND)
        self.SetSizer(sizer)
  
  
class MainFrame(wx.Frame):
  
    def __init__(self):
        wx.Frame.__init__(self, parent=None, title='TreeCtrl Demo')
        panel = TreePanel(self)
        self.Show()
  
  
if __name__ == '__main__':
    app = wx.App(redirect=False)
    frame = MainFrame()
    app.MainLoop()

输出：

Invalid Tree Item