Java Magazine - January/February 2012

LISTING 7

Figure 4

Figure 5

crazy with JLayer by building a magnifying glass that will magnify whatever is underneath the mouse as the mouse moves, as shown in Figure 6.

The code shown in Listing 7 is roughly the same as before. The difference is that this time it scales the graphics before drawing into an image. Then it draws the image back to the screen with a nice round clip.

Drawing components into a temporary image is a really useful technique because there are so many ways to post-process an image. To further extend the magnifying glass, you could add a distortion filter to give the scaled image a rounded effect.

@Override
public void paint(Graphics g, JComponent c) {
//draw regular
super.paint(g,c);

//draw into buffer Graphics2D g2 = img.createGraphics(); int ih = img.getHeight(); int iw = img.get Width();

//fill with white g2.setPaint(Color.WHITE); g2.fillRect(0, 0, img.get Width(), img.getHeight());

//render view component scaled and translated Graphics2D g3 = (Graphics2D) g2.create(); g3.translate(-pt.x + iw, -pt.y + ih* 2); g3.scale( 2, 2); g3.translate(-pt.x/2 - iw/4, -pt.y/2 - ih/4); super.paint(g3,c); g3.dispose();

//draw black border g2.setPaint(Color.BLACK); g2.setRenderingHint( RenderingHints.KEY_ANTIALIASING, RenderingHints.

VALUE_ANTIALIAS_ON); g2.setStroke(new BasicStroke( 3)); g2.draw(new Ellipse2D.Double(0,0,iw,ih)); g2.drawRect(0,0, iw- 1, ih- 1); g2.dispose();

//draw image to screen Shape oldClip = g.getClip(); int mx = pt.x-img.get Width()/2; int my = pt.y-img.getHeight(); g.setClip(new Ellipse2D.Double(mx,my,iw,ih)); g.drawImage(img, mx, my, null); g.setClip(oldClip);

}

COMMUNITY JAVA IN ACTION

Conclusion

JLayer is a very powerful addition to Swing that makes many previously hard or impossible effects easy to do in a clean and supported way. JLayer proves that Swing still has a lot of life left in it, and Java SE 7 provides new ways of extending Swing to do interesting things. (And being more generified is always nice, too.)

The examples shown here are just the tip of the iceberg. You could use JLayer to implement status overlays, busy indicators, global right-click menus, and much more. </article>

ABOUT US

Figure 6

that final image to the screen. Figure 4 shows an example of a button that can be blurred, and Figure 5 shows a blurred button.

Because the JLayer repaints any time its view control changes, we don’t need to track any state. A toggle button can simply toggle the enabled property of the button, and Swing takes care of the rest.