Swing Hacks

Build a Colorful Vector-Based Button #62

Chapter 8, Rendering

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315

HACK

g2.drawRoundRect(

(int)x, (int)y,

(int)w, (int)h,

(int)ax, (int)ay

);

}

Finally, you may have noticed the

pressed

boolean in

drawLiquidButton( )

.

JButton provides a way of knowing when the button has been selected, but

there is no way to know when it is pressed or released during the clicking

process. Most applications have no need for this information, but because

this hack involves rendering changes, you’ll need to know the pressed state

in order to draw the button properly. Since

JButton

doesn’t tell you the cur-

rent state, you have to detect it with a mouse listener that looks for press

and release events:

/* mouse listener implementation */

protected boolean pressed = false;

public void mouseExited(MouseEvent evt) { }

public void mouseEntered(MouseEvent evt) { }

public void mouseClicked(MouseEvent evt) { }

public void mouseReleased(MouseEvent evt) {

pressed = false;

}

public void mousePressed(MouseEvent evt) {

pressed = true;

}

Hacking the Hack

The VectorButton takes an awful lot of drawing code. This isn’t so much

because it scales, but simply because recreating the work of Apple’s talented

graphic designers with Swing code is difficult. One possible improvement

would be to use SVG files instead of direct Java2D code. This would let you

develop the actual look of the button in a graphics program instead of the

slow code/compile/run cycle we are all used to as programmers. It would

also let you pass the work on to a real graphic designer while you focus on

speed and functionality.

VectorButton shows the potential of vector-based interfaces, but it’s just the

tip of the iceberg. Imagine if you had an entire Look and Feel based on vec-

tors, where all the buttons scaled according to the font size. Then you could

change the font size to scale the entire application—while it’s running! You

could even do proper DPI calculations based on the physical size and shape

of the user’s screen to make your application look identical on any device,

scaling from PDAs all the way up to high resolution HDTVs.