--- On Wed, 9/17/08, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
> From: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
> Subject: [The Java Posse] Re: Componentized Designs
> To: "The Java Posse" <[email protected]>
> Date: Wednesday, September 17, 2008, 3:31 AM
> Hi Alexey,
>
> In the end, don't you expose exactly the same API
> whether you derive
> from JComponent or return JComponent via an accessor
> method?
Actually, no. The difference is in how the client code sees it. Consider the
following:
public class MyButton extends JButton
{
...
}
public class MyButtonComponent implements MyComponentInterface
{
public JComponent getComponent()
{
// returns JButton... maybe
}
}
If I'm working against MyButton, there is a whole set of API I am guaranteed of
having access to, whereas if I'm working against MyButtonComponent, I am given
just the API the author of MyButtonComponent and its framework deemed
appropriate in that context.
Now look what happens if the widget I'm working with suddenly needs to be
changed (either at compile time or maybe even at runtime). In the case of
MyButton, the onus is on whoever's doing the painting and layout. Maybe it's
MyButton class itself, or maybe (more along the Swing philosophy) some
implementation of ButtonUI.
But if I'm working against MyButtonComponent, I can simply switch delegation
logic between whatever kind of widget seems appropriate at the time. Now, this
isn't without problems of course. If we're plugging this into the existing
Swing world, we have to be very very cautious of event handling. Since we no
longer allow the client to register their UI-specific event listeners (such as
ActionEventListener), we have to build in a level of indirection and expose
appropriate events from whatever widget delegate we're using at the time. But
this isn't much different of a problem than what we'd potentially be faced with
if we were building a complex widget by inheriting off a composite widget
class, such as JPanel that's allowed to contain whatever combination of widgets
we really want to do the painting.
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups "The
Java Posse" group.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at
http://groups.google.com/group/javaposse?hl=en
-~----------~----~----~----~------~----~------~--~---
