Swing Hacks

Indefinite Progress Indicator #47

Chapter 6, Transparent and Animated Windows

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251

HACK

private void setBrightness(float multiple) {

float[] brightKernel = { multiple };

RenderingHints hints = new RenderingHints(RenderingHints.KEY_RENDERING,

RenderingHints.VALUE_RENDER_QUALITY);

BufferedImageOp bright = new ConvolveOp(new Kernel(1, 1, brightKernel),

ConvolveOp.EDGE_NO_OP, hints);

bright.filter(originalImage, convolvedImage);

repaint( );

}

The parameter multiple tells the method how many times brighter than the

original the resulting image must be. To achieve this effect, you can simply

perform a convolve operation on the original image. The kernel contains a

single value,

multiple. When the filter( ) method is invoked, every pixel

value of the original image is multiplied by the value of the kernel, making it

brighter. The result is stored in

convolveImage. It is now easy to use the

AnimatedPanel in an application:

Icon icon = UIHelper.readImageIcon("network.png");

AnimatedPanel animated = new AnimatedPanel("Waiting in vain...", icon);

getContentPane( ).add(animated);

animated.start( );

Besides the start( ) method, you can call stop( ) to interrupt the animation

thread when the task is done. This panel can be very efficient when used

with a

CardLayout. As this layout lets you stack components, you can put a

form on top of the animated panel. When the user performs an action, you

can display the animated panel and start the animation. At the end of the

task, you just need to stop the animation and hide the animated panel.

The example file Demo.java contains a complete example

using

CardLayout.

The Glass Pane as an Indicator

Using the AnimatedPanel proves to be efficient in form-oriented applica-

tions. Unfortunately, it does not help much when the running task must not

be interrupted by any action performed by the user. In this case, you need a

way to disable the entire GUI while displaying an indefinite progress indica-

tor. This can be done with a glass pane, as shown in Figure 6-16.

InfiniteProgressPanel is an animated glass pane you can set up on any

Swing frame:

InfiniteProgressPanel glassPane = new InfiniteProgressPanel( );

setGlassPane(glassPane);

glassPane.start( );

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Chapter 6, Transparent and Animated Windows

#47 Indefinite Progress Indicator

HACK

When you start( ) the panel, a fade-in animation is played during the ramp-

up phase. When

stop( ) is called, a fade-out animation is played. Between

the two, a circular shape is rotated at the center of the glass pane. All the

while, a white translucent veil is drawn over the underlying UI to disable it

visually.

The implementation of

InfiniteProgressPanel relies on many parameters,

which you can specify with the various constructors:

text

The optional message to be displayed below the circular shape

barsCount

The number of bars composing the circular shape

shield

The opacity of the white veil, also known as the shield

fps

The requested amount of frames per second during the animation

rampDelay

The time, in milliseconds, that fade-in and fade-out animations should

last

Figure 6-16. InfiniteProgressPanel draws a white veil to disable the UI visually