Re: Re: JPanel used for graphics

The problem with that is that it's frequently useful to rerender the xml 
to reset the variables in a class or set them to something new from 
dynamically generated xml. Yes you Could create a new instance of a 
class and do it in there...but, at least in the cases I've encountered, 
I've already had the class loaded and didn't want to screw around with  
a new instance.

This is, of course, very much an edge case. You average user isn't going 
to do what I was doing.

-Kate

[email protected] wrote:

> Frank,
> Here's a clarification.
> I had proposed a simple way to use subclassed components by allowing 
> the user to intitialize them.  My original text was
>
>> The Swix engine could check to see if a variable to which a tag is 
>> bound already has a non-null value.  If it's null, then it should 
>> create a new instance as it does now.  If it's non-null and it's an 
>> instance of the appropriate type, then the xml attributes should be 
>> applied to the existing value.  I'm not sure whether it's an easy 
>> solution to any other problems, but it would be a simple solution to 
>> my subclassing problem.
>
>
> Here are some snippets of code to illustrate what I mean more concretely.
> === From XML file =======================
> <!-- I want a panel (xc_panel) in the frame, but really want it to be a
>    Diagram (subclass of JPanel).  See below. -->
> . . .
> <panel id="xc_panel" preferredSize="500,500" 
> constraints="BorderLayout.CENTER">
> </panel>
> . . .
> === From Diagram.java =============================
> // This is the subclass of JPanel that I want xc_panel to be.
> public class Diagram extends JPanel {
> . . .
>   public paintComponent(Graphics g) {
>      // Draw my diagram to repaint the panel.
>      . . .
>   }
> }
> === From my main class ===========================
> // A possible solution is the following.  Note that THIS DOES NOT WORK
> // because Swixml always creates a new JPanel from the xml file
> // and overwrites my assignment to xc_panel.
> public class MyController {
>   . . .
>   public Diagram xc_panel;   // This is initialized by swixml
>   . . .
>   public MyController() {
>       xc_panel = new Diagram();   // I WOULD LIKE THIS TO WORK.
>       SwingEngine swix = new SwingEngine( this );
>       swix.render( "XXX.xml" );
>       . . . // render() has assigned a new panel to xc_panel :-(
>   }
> . . .
> The Diagram/JPanel variable xc_panel is specified in the .xml and
> initialized by the swix.render call.  What I'd prefer the SwingEngine
> to do it take a look at the contents of xc_panel before it creates
> a new JPanel.  If xc_panel already contains a JPanel, as my example
> does, it should not create a new one, but use the existing one and
> simply apply any specifed attributes to it -- in my case a preferred
> size of 500x500 was specified.
> This appears to be a simple solution to my problem where I must subclass
> JPanel to override paintComponent().  I believe allowing user 
> initialization
> of components might also provide a solution to problems that initclass 
> can't
> easily solve.
> -- Fred
>
>
>
>
>
>
> [email protected] writes:
>
>> List for Users of Carlsbad Cubes' Technologies and Products schrieb 
>> am 27.03.04 18:16:58:
>>
>>>
>>> It appears that the way to do this is to register a new tag for this 
>>> subclass of JPanel that I've defined.  Is this the correct approach? 
>>
>>
>> At least this seems the most reasonable thing to me.
>> Easy, documented and IMHO well used.
>>
>>>
>>> This got me to thinking about other approaches.  The Swix engine 
>>> could check to see if a variable to which a tag is bound already has 
>>> a non-null value.  If it's null, then it should create a new 
>>> instance as it does now.  If it's non-null and it's an instance of 
>>> the appropriate type, then the xml attributes should be applied to 
>>> the existing value.  I'm not sure whether it's an easy solution to 
>>> any other problems, but it would be a simple solution to my 
>>> subclassing problem. 
>>
>>
>> Could you please explain this with some (pseudo) code? I do not
>> grab it...
>> Frank
>>  
>>
>>
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>
>
>
>
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