In order to improve usability, it is good to support drag and drop in an application so that the user can simply drop files or other objects into your application. This recipe will show how to support accepting a CompositeDataObject that supports both files and text.
First we will define a custom drop target class:
class FileAndTextDropTarget(wx.PyDropTarget):
"""Drop target capable of accepting dropped
files and text
"""
def __init__(self, file_callback, text_callback):
assert callable(file_callback)
assert callable(text_callback)
super(FileAndTextDropTarget, self).__init__()
# Attributes
self.fcallback = file_callback # Drop File Callback
self.tcallback = text_callback # Drop Text Callback
self._data = None
self.txtdo = None
self.filedo = None
# Setup
self.InitObjects()
def InitObjects(self):
"""Initializes the text and file data objects"""
self._data = wx.DataObjectComposite()
self.txtdo = wx.TextDataObject()
self.filedo = wx.FileDataObject()
self._data.Add(self.txtdo, False)
self._data.Add(self.filedo, True)
self.SetDataObject(self._data)
def OnData(self, x_cord, y_cord, drag_result):
"""Called by the framework when data is dropped
on the target
"""
if self.GetData():
data_format = self._data.GetReceivedFormat()
if data_format.GetType() == wx.DF_FILENAME:
self.fcallback(self.filedo.GetFilenames())
else:
self.tcallback(self.txtdo.GetText())
return drag_resultThen to make use of the FileAndTextDropTarget, we assign it to a window using the window object's SetDropTarget method.
class DropTargetFrame(wx.Frame):
def __init__(self, parent, id=wx.ID_ANY, title="",
pos=wx.DefaultPosition, size=wx.DefaultSize,
style=wx.DEFAULT_FRAME_STYLE,
name="DropTargetFrame"):
super(DropTargetFrame, self).__init__(parent, id,
title, pos,
size, style,
name)
# Attributes
choices = ["Drag and Drop Text or Files here",]
self.list = wx.ListBox(self,
choices=choices)
self.dt = FileAndTextDropTarget(self.OnFileDrop,
self.OnTextDrop)
self.list.SetDropTarget(self.dt)
# Setup
self.CreateStatusBar()
def OnFileDrop(self, files):
self.PushStatusText("Files Dropped")
for f in files:
self.list.Append(f)
def OnTextDrop(self, text):
self.PushStatusText("Text Dropped")
self.list.Append(txt)
The framework will call the OnData method of our DropTarget when the window has received the drop data. When OnData is called, we simply get the data from our DataObject and pass it to the appropriate callback function to let our window decide how to handle the data.
All window objects have a SetDropTarget
method that can be used to assign a DropTarget, so this class can be reused for almost any type of control. In the previous example, we assigned it to a ListBox and then appended the dropped data to the list in each of our callbacks.
The PyDropTarget class provides a few more methods that can be called at different times during the drag operation. These methods can also be overridden in order to do things such as change the mouse cursor, show a custom drag image, or reject the drag object.
|
Methods |
When the methods are called |
|---|---|
|
Called when a drag object enters the window. Returns a drag result value (that is, | |
|
Called while the mouse is dragging the object over the target | |
|
Called when the mouse leaves the drop target | |
|
Called when the user drops the object. Return | |
|
Called after |