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" +

"you could remember your password this time?",

JOptionPane.ERROR_MESSAGE,

JOptionPane.OK_OPTION);

JDialog d = pane.createDialog (null, "Shakin'!");

DialogEarthquakeCenter dec = new DialogEarthquakeCenter (d);

d.pack( );

d.setModal (false);

d.setVisible(true);

dec.startShake( );

// wait (forever) for a non-null click and then quit

while (pane.getValue( ) == JOptionPane.UNINITIALIZED_VALUE ) {

try { Thread.sleep(100); }

catch (InterruptedException ie) {}

}

System.exit(0);

}

The main( ) method builds a JOptionPane dialog through what can only be

called “the other way.” Most developers will call

JOptionPane.show...

Dialog( )

because it’s convenient to get the dialog on screen immediately and

provide the user’s selection as a return value, and because it’s not necessary