JInternalFrame problem

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Jonathan Kapleau - 09 Jun 2004 18:08 GMT

I create a JInternalFrame and add it to the JDesktopPane

JDesktopPane desktop = new JDesktopPane();
...
desktop.add(new MyJInternalFrame());

but when I call "getDesktopPane()" from within the new JInternalFrame
the method returns null. What am I doing wrong?

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Fred L. Kleinschmidt - 10 Jun 2004 15:13 GMT

> I create a JInternalFrame and add it to the JDesktopPane
>
[quoted text clipped - 4 lines]
> but when I call "getDesktopPane()" from within the new JInternalFrame
> the method returns null. What am I doing wrong?

And just how do you call getDesktopPane() from that new JInternalFrame?
You did not keep a reference to the MyInternalFrame added to desktop.

Signature

Fred L. Kleinschmidt
Boeing Associate Technical Fellow
Technical Architect, Common User Interface Services
M/S 2R-94 (206)544-5225

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Jonathan Kapleau - 10 Jun 2004 20:02 GMT

> > I create a JInternalFrame and add it to the JDesktopPane
> >
[quoted text clipped - 7 lines]
> And just how do you call getDesktopPane() from that new JInternalFrame?
> You did not keep a reference to the MyInternalFrame added to desktop.

My bad. I subclass the JInternalFrame and from within the code for
MyInternalFrame I call it as:

this.getDesktopPane();

besides, can't I get refences to all the JInternalFrames from the
JDesktopPane?

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Fred L. Kleinschmidt - 11 Jun 2004 15:26 GMT

> > > I create a JInternalFrame and add it to the JDesktopPane
> > >
[quoted text clipped - 12 lines]
>
> this.getDesktopPane();

This will not work if you are calling getDesktopPane() from the
MyJInternalFrame constructor, since the MyJInternalFrame is not added to
the desktop until after the constructor finishes - the above is somewhat
equivalent of:

MyJInternalFrame myframe = new MyJInternalFrame();
desktop.add( myframe );
myframe = null;

> besides, can't I get refences to all the JInternalFrames from the
> JDesktopPane?

Which object really needs to refer explicitly to the internal frame -
desktop, or the class in which the desktop resides? If you have multiple
JInternalFrames in the desktop, then, sure, you can use
desktop.getAllFrames() to retrieve them, but then you have to figure out
which of them to use for some specific operation. Why not just keep the
reference when you create the JInternalFrame?

Signature

Fred L. Kleinschmidt
Boeing Associate Technical Fellow
Technical Architect, Common User Interface Services
M/S 2R-94 (206)544-5225

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Jonathan Kapleau - 12 Jun 2004 02:53 GMT

> > My bad. I subclass the JInternalFrame and from within the code for
> > MyInternalFrame I call it as:
[quoted text clipped - 9 lines]
> desktop.add( myframe );
> myframe = null;

Thanks, this is something I had not considered. Does this still apply
if the MyJInternaFrame constructor calls another method? For example:

public MyJInternalFrame() {

...

launch();
}

void launch() {

...

getDesktopPane();
}

Thanks.

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Lou Lipnickey - 11 Jun 2004 14:05 GMT

I had a similar problem with this awhile ago. Are you running this as an
applet or as an application (.java)? I was running as an application and
remember reading about a bug relative to the application. However, if
applet was extended (vs jframe), and incorporated other classes to
extend JFrame, the whole thing worked. - Lou

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JInternalFrame problem

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