[ajug-members] Swing and garbage collection

[Donald Bleyl]

John,

A common idiom (for lack of a better word) with Swing apps is to have one 
parent JFrame, a
lightweight class w/ main method for bootstraping the program (and no 
fields), and a few helper classes that resemble SwingUtilities to manage 
functionality that doesn't belong in any one class. An example would be a 
WindowUtilities class that provides a center(Window) function.  Whether you 
use Singleton or static methods is an implementation detail.

The helper classes tend to add some generic functionality and not much 
state.  Similarly, a resource class can be used to externalize strings, load 
icons, etc.  For persisting
user preferences, checkout the Preferences API, which is easy to use and 
stores  info in the
registry when used on Windows.  Also, if you are doing Swing, it's essential 
to get your head around
the threading issues.

Foxtrot is a library that makes Swing threading easier, and is easy to use 
itself:
http://foxtrot.sourceforge.net/
The documentation describes the catch 22's of Swing threading.

Also,you should  use setVisible(boolean) instead of show/hide, which are 
deprecated as of 1.1.

>I have a swing application that is started by running a class called
>MainApp.  The class has a main method that creates an object of itself,
>creates a number of different JFrames and populates a few of its own
>fields with various objects.  It's never meant to be seen...more of a
>common entry way into the application.
>
>The problem is that I'd like it to remain in scope, so that the fields
>that it instantiates are accessible for the entire lifetime of the
>application.  This is because it creates a few common resources ( a system
>tray icon if it's run on Windows, for example).
>
>What's the accepted standard for persisting things like this in swing?
>What is this even called, so that I might google efficiently?  Currently,
>as soon as the execution thread has passed through it, it's gone.  I tried
>causing it to extend JFrame and calling objectname.hide(), but no luck,
>still garbage collected.
>
>Thanks for the help!
>
>John
>
>
>
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