Swing Hacks

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Chapter 5, Windows, Dialogs, and Frames

#39 Spin Open a Detail Pane

HACK

to ever have a reference to the dialog. With DialogEarthquakeCenter, how-

ever, you need that reference. So, instead, you provide the usual

JOptionPane

values (message, message type, user options, etc.) to the

JOptionPane

con-

structor, and then derive a dialog with

createDialog( )

. Don’t worry—you

still end up with the same option dialog.

Next, you create a

DialogEarthquakeCenter

from that dialog. Then you can

return to the dialog,

pack( ) it, and make it visible. One hazard of working

with the

JOptionPane dialog is that it is modal, meaning it will block the

AWT event-dispatch thread when shown; thus, it won’t shake because

DialogEarthquakeCenter won’t get any animation callbacks from Timer. To

get around this, I just made the dialog non-modal—after all, the user proba-

bly isn’t going to be able to click it when it’s moving. Another option might

be for the

DialogEarthquakeCenter constructor to remember if its dialog is

modal, and to reset this state in

stopShake( ).

Unfortunately, there’s not a great way to show the effect of this animation in

book form. The best I can suggest is that you compile and run the hack for

yourself. While you’re at it, change some of the constant values to see the

effect of longer or shorter shake cycles, distances, and durations.

H A C K

#39

Spin Open a Detail Pane Hack #39

You don’t want to bombard the user with details, but you don’t want to hide

them either. Here’s a way to let the user pop open a More Info widget.

You have to be careful not to weigh down your GUIs with so much informa-

tion that the user can’t see what really matters. On the other hand, there are

times that the user may want more information than is obvious on one

screen or panel. A simple way of dealing with this is to put a More Info but-

ton that pops up a new window. That leads to the annoyance of having too

many windows on the screen, none associated in any way with their source.

Mac OS X has a nice idea: the spin open disclosure widget. It works like

this: you have a component of some sort—perhaps a simple label or a com-

plex panel—with a triangle-shaped spinner below it. When the user clicks

the spinner, a whole new widget opens up below the spinner, offering more

information. In fact, the new widget can have significant functionality: to set

file permissions from the Finder, you open a Get Info window and spin open

an Ownership and Permissions section to set your own access (if you own

the file), and a second Details spinner lets you set access levels for the

owner, group, and others.