Swing Hacks

Indefinite Progress Indicator #47

Chapter 6, Transparent and Animated Windows

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HACK

To make things clearer, this code does not contain the painting of the text.

To allow the glass pane to be visible even when the animation is not started,

the application first checks the value of

started

. When false,

start( )

has

not been called yet and nothing must be drawn. In the other case, the white

veil is first painted all over the glass pane. The fourth parameter of the

Color

object used by

fillRect( )

defines the opacity. Opacity depends on two

parameters here:

shield and alphaLevel. The latter is computed by the ani-

mation thread to fade in and fade out the glass pane. As

alphaLevel is

between 0 and 255, and you multiply it by

shield, which is in the range 0.0

to 1.0, to obtain the opacity of the veil. Finally, the

for

loop computes a new

color for each bar and paints it. The colors are computed so as to create a

circular gradient and give an impression of movement when the circular

shape is rotated.

Run the Animation Thread

The most complicated part of InfiniteProgressPanel is the Animator thread

since its

run( ) method handles the fade-in and -out animations, as well as

the main animation. The only constructor of

Animator requires a boolean

parameter called

rampUp. When true, the thread will play both main and

fade-in animations. Otherwise, the fade-out animation is played. This is

what happens when you call

InfiniteProgressPanel.stop( ...