如何检查项是否已被放置？wxpython？

Question

在使用wxpython的拖放功能时，有没有办法在文本被放下时执行一个函数？我想要的类似于绑定的功能。但网上似乎没有相关的例子。

通过调用SetDataObject将一个wxDataObject绑定到放置目标。你还需要在放置目标实例中保留一个指向wxDataObject的指针，这样你就可以在OnData方法中调用wxDataObject.GetData()。

不过我对这句话完全不明白。

__author__ = 'David Woods, Wisconsin Center for Education Research <dwoods@wcer.wisc.edu>'

# Import wx.Python
import wx
# Declare GUI Constants
MENU_FILE_EXIT = wx.NewId()
DRAG_SOURCE    = wx.NewId()

# Define Text Drop Target class
class TextDropTarget(wx.TextDropTarget):
   """ This object implements Drop Target functionality for Text """
   def __init__(self, obj):
      """ Initialize the Drop Target, passing in the Object Reference to
          indicate what should receive the dropped text """
      # Initialize the wx.TextDropTarget Object
      wx.TextDropTarget.__init__(self)
      # Store the Object Reference for dropped text
      self.obj = obj

   def OnDropText(self, x, y, data):
      """ Implement Text Drop """
      # When text is dropped, write it into the object specified
      self.obj.WriteText(data + '\n\n')

# Define File Drop Target class
class FileDropTarget(wx.FileDropTarget):
   """ This object implements Drop Target functionality for Files """
   def __init__(self, obj):
      """ Initialize the Drop Target, passing in the Object Reference to
          indicate what should receive the dropped files """
      # Initialize the wxFileDropTarget Object
      wx.FileDropTarget.__init__(self)
      # Store the Object Reference for dropped files
      self.obj = obj

   def OnDropFiles(self, x, y, filenames):
      """ Implement File Drop """
      # For Demo purposes, this function appends a list of the files dropped at the end of the widget's text
      # Move Insertion Point to the end of the widget's text
      self.obj.SetInsertionPointEnd()
      # append a list of the file names dropped
      self.obj.WriteText("%d file(s) dropped at %d, %d:\n" % (len(filenames), x, y))
      for file in filenames:
         self.obj.WriteText(file + '\n')
      self.obj.WriteText('\n')

class MainWindow(wx.Frame):
   """ This window displays the GUI Widgets. """
   def __init__(self,parent,id,title):
       wx.Frame.__init__(self,parent,-4, title, size = (800,600), style=wx.DEFAULT_FRAME_STYLE|wx.NO_FULL_REPAINT_ON_RESIZE)
       self.SetBackgroundColour(wx.WHITE)

       # Menu Bar
       # Create a MenuBar
       menuBar = wx.MenuBar()
       # Build a Menu Object to go into the Menu Bar
       menu1 = wx.Menu()
       menu1.Append(MENU_FILE_EXIT, "E&xit", "Quit Application")
       # Place the Menu Item in the Menu Bar
       menuBar.Append(menu1, "&File")
       # Place the Menu Bar on the ap
       self.SetMenuBar(menuBar)
       #Define Events for the Menu Items
       wx.EVT_MENU(self, MENU_FILE_EXIT, self.CloseWindow)

       # GUI Widgets
       # Define a Text Control from which Text can be dragged for dropping
       # Label the control
       wx.StaticText(self, -1, "Text Drag Source  (left-click to select, right-click to drag)", (10, 1))
       # Create a Text Control
       self.text = wx.TextCtrl(self, DRAG_SOURCE, "", pos=(10,15), size=(350,500), style = wx.TE_MULTILINE|wx.HSCROLL)
       # Make this control a Text Drop Target
       # Create a Text Drop Target object
       dt1 = TextDropTarget(self.text)
       # Link the Drop Target Object to the Text Control
       self.text.SetDropTarget(dt1)
       # Put some text in the control as a starting place to have something to copy
       for x in range(20):
          self.text.WriteText("This is line %d of some text to drag.\n" % x)
       # Define Right-Click as start of Drag
       wx.EVT_RIGHT_DOWN(self.text, self.OnDragInit)

       # Define a Text Control to recieve Dropped Text
       # Label the control
       wx.StaticText(self, -1, "Text Drop Target", (370, 1))
       # Create a read-only Text Control
       self.text2 = wx.TextCtrl(self, -1, "", pos=(370,15), size=(410,235), style = wx.TE_MULTILINE|wx.HSCROLL|wx.TE_READONLY)
       # Make this control a Text Drop Target
       # Create a Text Drop Target object
       dt2 = TextDropTarget(self.text2)
       # Link the Drop Target Object to the Text Control
       self.text2.SetDropTarget(dt2)

       # Define a Text Control to recieve Dropped Files
       # Label the control
       wx.StaticText(self, -1, "File Drop Target (from off application only)", (370, 261))
       # Create a read-only Text Control
       self.text3 = wx.TextCtrl(self, -1, "", pos=(370,275), size=(410,235), style = wx.TE_MULTILINE|wx.HSCROLL|wx.TE_READONLY)
       # Make this control a File Drop Target
       # Create a File Drop Target object
       dt3 = FileDropTarget(self.text3)
       # Link the Drop Target Object to the Text Control
       self.text3.SetDropTarget(dt3)

       # Display the Window
       self.Show(True)

   def CloseWindow(self, event):
       """ Close the Window """
       self.Close()

   def OnDragInit(self, event):
       """ Begin a Drag Operation """
       # Create a Text Data Object, which holds the text that is to be dragged
       tdo = wx.PyTextDataObject(self.text.GetStringSelection())
       # Create a Drop Source Object, which enables the Drag operation
       tds = wx.DropSource(self.text)
       # Associate the Data to be dragged with the Drop Source Object
       tds.SetData(tdo)
       # Intiate the Drag Operation
       tds.DoDragDrop(True)


class MyApp(wx.App):
   """ Define the Drag and Drop Example Application """
   def OnInit(self):
      """ Initialize the Application """
      # Declare the Main Application Window
      frame = MainWindow(None, -1, "Drag and Drop Example")
      # Show the Application as the top window
      self.SetTopWindow(frame)
      return True


# Declare the Application and start the Main Loop
app = MyApp(0)
app.MainLoop()

wxpython 拖放功能用户界面设计事件绑定数据对象放置目标 wxDataObject OnData方法

如何检查项是否已被放置？wxpython？

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