There are two ways to create your own widgets with Tkinter: subclass from an
existing widget or construct your new widget in a Frame. Subclassing from a
Frame is the more general method. Subclassing an existing widget is usually
only useful if you are creating a specialized version of an existing widget.
If your widget is a composite of two or more existing widgets (often called
a megawidget), you should almost always use the Frame approach.
Alternatively you can use a widget-building framework such as PMW.
Here's how to get started: In your constructor you first initialize the
superclass then create your childwidgets. The parent of the subwidgets is
self.
class ScrolledList( Tkinter.Frame ):
def __init__( self, parent, **options ):
Tkinter.Frame.__init__( self, parent, **options )
self._list = Tkinter.List( self )
self._scrollbar = Tkinter.Scrollbar( self )
self._list.pack( side=Tkinter.LEFT )
self._scrollbar.pack( side=Tkinter.LEFT )
This allows your widget to behave like any other widget. That is to use
your widget, you construct it:
myWidgetInstance = ScrolledList( aParentWidget, ... )
Then you pack, grid or place it to display it.
myWidgetInstance.pack( )
If you want to allow your widget to handle its own custom widget options,
you need to pull these options out of the **options argument before calling
Tkinter.Frame.__init__( ... ).
If you don't like the .pack() methods being in __init__, you could override
pack(), grid() and place() and pack the list and scrollbar there instead.
Hope this helps
----- Original Message -----
From: "vtcodger" <[EMAIL PROTECTED]>
To: <tkinter-discuss@python.org>
Sent: Sunday, August 03, 2008 5:34 PM
Subject: [Tkinter-discuss] Creating a new widget class
I wonder if someone who understands Python and Tkinter a bit better than I
could help me out. Basically, I'm trying to encapsulate the kind of messy
stuff associated with setting up a listbox with a scrollbar in a Python
class. From my probably incredibly naive point of view, it doesn't look
too
hard.
class ScrolledList(Frame,Listbox,Scrollbar) :
#At this point we have a template for objects that have all the
#attributes and methods of Frames,Listboxes,and Scrollbars. For
#names that occur in all, the Frame version takes precedence over
#the Listbox version and that in turn takes precedence over
#Scrollbar version
def __init__ (self, Tkobject, height=4, width=50) :
#This code is executed whenever a new scrolled list object is
#created (instantiated)
self.f = Frame(Tkobject)
s = Scrollbar(self.f,orient=VERTICAL)
self.l = Listbox(self.f, height=height, width=width,
yscrollcommand=s.set, exportselection=0)
#We have now created a frame, scrollbar and listbox
s.config(command=self.l.yview)
s.pack(side=RIGHT, fill=Y); self.l.pack()
#And configured the listbox and scrollbar to interact
And it creates a Tkinter object with a gazillion attributes.
Unfortunately
tk isn't one of them. When I try to invoke the methods, I am informed
that
the new object has no 'tk' attribute. That's correct. It doesn't.
Apparently I have failed to call some necessary constructor. But which?
Maybe I'm close to having it right because if I create a grid attribute in
the class and pass the parameters to the frame grid method, the scrolled
listbox can be configured and displayed.
def grid(self,row=90,column=1,rowspan=5,columnspan=4,sticky=W) :
self.f.grid(row=row,column=column,rowspan=rowspan,columnspan=columnspan,sticky=sticky)
What am I doing wrong, or not doing right?
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