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Using a JProgressBar

Posted on 2004-09-26
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Last Modified: 2008-02-01
hello!

I want to use a JProgressBar in a splash screen of a java program i am writing. The program at the start reads some text files, processes them etc. I want to indicate how much of the processing is done by using a JProgressBar, so the user essentially knows how much is left before the main GUI part of the app shows.

How can i determine the length of the task? How is it usually done, currently, the only way i am aware of tackling this problem is to increment the progress bar by 1 in different locations of the code untill i finally have incremented to 100 (the max value of the JProgressBar i want to use) at the end of the task. To me this seems tedious and very unprofessional, i was wondering how professional java developers would indicate how much of a task is complete using a JProgressBar.

Thx for any tips or help.
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Question by:Mr_A_Smith
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4 Comments
 
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by:CEHJ
ID: 12154386
If the length of the processing is not known, you'll have to setDeterminate(false) on the JProgressBar
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TrekkyLeaper earned 30 total points
ID: 12154387
The way I have done it involves a couple steps:

1. You need to come up with some sort of metric for measuring your progress. This may be something like files loaded / total files, distinct loading operations / total, etc.
2. Once you have that, I would make the splash screen (or a subclass of the progress bar would be even better) an Observer of your loading system.

Observer: http://java.sun.com/j2se/1.4.2/docs/api/java/util/Observer.html
Observable: http://java.sun.com/j2se/1.4.2/docs/api/java/util/Observable.html
Java Almanac: http://javaalmanac.com/egs/java.util/Obs.html

Then, whenever your loading model reaches a new checkpoint, you can do something like:

setChanged();
notifyObservers( new Integer( myProgress ) );
clearChanged();

In the Observer's update method, the Integer passed in will be the second argument. You can take that and adjust the progress bar.

I hope this makes sense.
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Expert Comment

by:CEHJ
ID: 12154389
Or rather

setIndeterminate(true);

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Expert Comment

by:TrekkyLeaper
ID: 12155280
=)
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