Swing Hacks

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Chapter 6, Transparent and Animated Windows

#47 Indefinite Progress Indicator

HACK

AffineTransform toWheel = new AffineTransform( );

toWheel.concatenate(toCenter);

toWheel.concatenate(toBorder);

primitive.transform(toWheel);

primitive.transform(toCircle);

ticker[(int) i] = primitive;

}

return ticker;

}

The buildTicker( ) method returns an array of Areas, where each Area is one

of the bars composing the resulting shape. A bar is built in

buildPrimitive( )

by merging two circles and a rectangle. The role of buildTicker( ) is simply

to create the requested amount of bars and to move them to their final

location. To do that, the code applies several

AffineTransform operations:

toCenter first translates the bar to the center of the glass pane, toBorder then

moves the bar to the perimeter of the circle you want to create, and

toCircle

finally rotates the bar around the glass pane’s center.

Paint the Indicator

Once ticker has been built, paintComponent( ) only needs to get each bar

and fill it on the graphics surface of the glass pane:

public void paintComponent(Graphics g)

{

if (started)

{

int width = getWidth( );

int height = getHeight( );

Graphics2D g2 = (Graphics2D) g;

g2.setRenderingHints(hints);

g2.setColor(new Color(255, 255, 255, (int) (alphaLevel * shield)));

g2.fillRect(0, 0, getWidth(), getHeight( ));

for (int i = 0; i < ticker.length; i++)

{

int channel = 224 - 128 / (i + 1);

g2.setColor(new Color(channel, channel, channel, alphaLevel));

g2.fill(ticker[i]);

}

}

}