Creating a Swing Dashboard Widget - Part 5 (Info Button)

Widgets have an info button which when pressed flips the widget over to the back so the user can edit their preferences.

It has a number of visual states:
- usually invisible
- when cursor is over the widget the 'i' fades in.
- when the cursor is over the button a background appears

Changing the state of the button's ButtonModel as the mouse cursor moves over various code is simple. The painting code looks at the model to decide what to paint.
Fading is more tricky, especially as the TimingFramework isn't integrated into the JDK.
So I just used a straight forward Swing Timer that varies the alpha value of the button 'i'. When the state changes the timer is kicked off, and for every timer beat the painting transparency is slightly altered until it's either completely transparent or completely opaque.
It would have been better to use a curve rather than the liner adjustment.

<br />public class InfoButton extends AbstractButton {<br /> private float textAlpha = 0f;<br /><br /> private Timer fadeTimer = new Timer(25, new ActionListener(){<br /> public void actionPerformed(ActionEvent ae){<br /> if (getModel().isRollover()) {<br /> textAlpha += 0.06;<br /> if (textAlpha >= 1f) {<br /> textAlpha = 1f;<br /> fadeTimer.stop();<br /> }<br /> }<br /> else {<br /> textAlpha -= 0.06;<br /> if (textAlpha <= 0f) {<br /> textAlpha = 0f;<br /> fadeTimer.stop();<br /> }<br /> }<br /> repaint();<br /> }<br /> });<br /><br /> public InfoButton(JComponent rolloverComp) {<br /> setOpaque(false);<br /> setSize(new Dimension(13, 13));<br /> setModel(new DefaultButtonModel());<br /> setFont(new Font("Serif", Font.BOLD | Font.ITALIC, 13));<br /><br /> addMouseListener(new MouseAdapter() {<br /> public void mouseClicked(MouseEvent e) {<br /> if (getShape().contains(e.getPoint()))<br /> fireActionPerformed(new ActionEvent(InfoButton.this,<br /> ActionEvent.ACTION_PERFORMED,<br /> "Info"));<br /> }<br /><br /> public void mouseEntered(MouseEvent e) {<br /> getModel().setArmed(true);<br /> getModel().setRollover(true);<br /> }<br /><br /> public void mouseExited(MouseEvent e) {<br /> getModel().setArmed(false);<br /> }<br /> });<br /><br /> rolloverComp.addMouseListener(new MouseAdapter() {<br /> public void mouseEntered(MouseEvent e) {<br /> getModel().setRollover(true);<br /> fadeTimer.start();<br /> }<br /><br /> public void mouseExited(MouseEvent e) {<br /> getModel().setRollover(false);<br /> fadeTimer.start();<br /> }<br /> });<br /> }<br /><br /> private Shape getShape() {<br /> return new Ellipse2D.Float(0, 0, getWidth() - 1, getHeight() - 1);<br /> }<br /><br /> @Override<br /> protected void paintComponent(Graphics g) {<br /> super.paintComponent(g);<br /> Graphics2D g2 = (Graphics2D)g.create();<br /> g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,<br /> RenderingHints.VALUE_ANTIALIAS_ON);<br /><br /> Shape disc = getShape();<br /><br /> // background<br /> if (getModel().isArmed()) {<br /> g2.setColor(new Color(1f, 1f, 1f, .2f));<br /> g2.fill(disc);<br /> }<br /><br /> // symbol<br /> g2.setFont(getFont());<br /> g2.setColor(new Color(1f, 1f, 1f, textAlpha));<br /> int iw = SwingUtilities.computeStringWidth(g2.getFontMetrics(), "i");<br /> g2.drawString("i", (getWidth() / 2) - (iw / 2),<br /> (getHeight() / 2) + g2.getFontMetrics().getHeight() / 2 -<br /> 2);<br /> }<br />}
So now I have this: