Swing Hacks

Indefinite Progress Indicator #47

Chapter 6, Transparent and Animated Windows

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247

HACK

Figure 6-11 shows the slide-in window on Mac OS X. It’s less appropriate

on the Mac, and it will be obscured if the user has dock magnification

turned on, but it’s not really bad either.

Hacking the Hack

To expand this hack, the first thing you’d probably want to do is add some

kind of

MouseListener so that if the user clicks to acknowledge the appear-

ance of the slide-in window, you could react to it by removing the slide-in

window, bringing your application’s main window to the front, etc. Then

again, you can put live components in here, so there’s no reason you

couldn’t just generate a

JOptionPane, make a JDialog from it, grab the con-

tent pane of that

JDialog, and show it in the slide-in window. That would

give you real, active Swing buttons and handy

JOptionPane return values.

After all, that’s what the sheet example did.

H A C K

#47

Indefinite Progress Indicator Hack #47

Despite its numerous advanced widgets, Swing offers no efficient way to

show that a task of unknown length is in progress. This hack presents two

solutions to address this issue.

Have you ever watched an application do something, but not tell you what

that something is? Other applications let you know what’s going on but

don’t really tell you how long they will need to complete the task. For

instance, the Microsoft Windows copy dialog is famous for its silly (and

lengthy) nonprogress indicators. As a user, I find this very annoying; as a pro-

grammer, I know how difficult it can be to determine the duration of a task.

The Swing Solution

To address this issue, developers created particular widgets meant to show a

task of unknown length is in progress. You can see such a widget in

Mozilla’s installer. It displays an indefinite progress bar—also called a

Cylon—in which a small rectangle bounces back and forth between the two

horizontal edges. I have also seen indefinite progress bars filling like regular

progress bars, going backward once filled and starting all over again. The

Figure 6-11. Slide-in window on Mac OS X with dock on bottom of screen (left) and not

on bottom (right)

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Chapter 6, Transparent and Animated Windows

#47 Indefinite Progress Indicator

HACK

idea of an indefinite progress bar is great, but most existing implementa-

tions are just wrong. Users know what a progress bar looks like, and they

also know how it is supposed to behave. It is a bad idea to present a familiar

widget acting in a very surprising way. Unfortunately, the Swing designers

followed this trend and added the

setIndeterminate(boolean)

method to

JProgressBar

. Check out Example 6-14.

This short example creates a new window containing an indefinite progress

bar. When you launch the program, you can see a small rectangle bouncing

back and forth within the progress bar’s bounds, as in Figure 6-12. The

result is much better on Mac OS X because it uses the native Look and Feel

automatically, as shown in Figure 6-13. Despite this visual improvement,

though, the result is still far from perfect.

There are several better ways to show that a task of unknown length is in

progress.

Example 6-14. An indefinite progress bar

import javax.swing.*;

public class CylonBar {

public static void main(String[] args) {

JFrame f = new JFrame("Progress");

JProgressBar p = new JProgressBar( );

p.setIndeterminate(true);

f.getContentPane( ).add(p);

f.pack( );

f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

f.setVisible(true);

}

}

Figure 6-12. The indefinite progress bar offered by Swing

Figure 6-13. Swing’s indefinite progress bar with Mac OS X Look and Feel