Swing Hacks

Earthquake Dialog #38

Chapter 5, Windows, Dialogs, and Frames

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201

HACK

So, that’s what happens in the actionPerformed( ) callback. The method

takes the elapsed time and figures out how far into a cycle it is (given a cycle

time of

SHAKE_CYCLE

), expressed as a

double

between

0

and

1

. Multiply this

by

2π

, and you’ve got an angle you can pass to

Math.sin( )

. Multiply that by

SHAKE_DISTANCE

, and you’ll have an x-offset in the range -

SHAKE_DISTANCE

≤

n

≤

SHAKE_DISTANCE

. Add that to the

naturalLocation

’s x-value, keep the natural

y-value, and you have the new location for the dialog. Call

setLocation( )

with this point and repaint( ).

actionPerformed( )

’s only other responsibility is to check to see if the anima-

tion time has expired and, if so, to call the

stopShake( ) method, which is

public and could thus be called by an outsider to end the animation prema-

turely.

stopShake( ) stops the Timer, returns the dialog to its natural loca-

tion, and

repaint( )s.

Shake, Rattle, and Roll

I’ve provided a main( ) method to demonstrate the DialogEarthquakeCenter.

To show its flexibility, I made it shake a

JOptionPane dialog, to prove you

can still use option dialogs as well as normal dialogs, although you do need

to work with option dialogs slightly differently:

public static void main (String[] args) {

JOptionPane pane =

new JOptionPane ("You've totally screwed up your login\n" +

"Go back and do it again... and do you think\n" ...