You know how macs make one button pulse?

[Nick George]

If you request focus on one button, you'll get a little blue circle around it. Macs also seem capable of making one button pulse blue, usually the OK button. As an example that is (I think) done in java, look at file -> properties in eclipse. Anyone know how to pulse like that?

Thanks,
Nick
[ June 17, 2008: Message edited by: Nick George ]

[pete stein]

One way to make colors pulse is to create a simple sin-wave of color change. In other words take your starting color and your finishing color and interpolate the colors in between so they fall on a sin curve. This makes for a nice smooth transition of color. For instance:

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;
 
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.Timer;
 
public class PulsingColor
{
  private static final int STEPS = 60;
  private static final int GREEN_VALUE = 0;
  private static final Font LABEL_FONT = new Font(Font.DIALOG, Font.BOLD, 48);
  private static final int DELAY = 24;
  private static final String TEXT = "Pulsing Color";
  private static final int PANEL_SIZE = 50;
  private Color[] colors = new Color[STEPS];
  private JLabel label = new JLabel(TEXT);
  private JPanel colorPanel = new JPanel();
  
  private JPanel mainPanel = new JPanel();
 

  public JPanel getMainPanel()
  {
    return mainPanel;
  }
 
  public PulsingColor()
  {
    initColors();
    label.setFont(LABEL_FONT);
    label.setForeground(colors[0]);
    
    colorPanel.setPreferredSize(new Dimension(PANEL_SIZE, PANEL_SIZE));
    
    mainPanel.add(label);
    mainPanel.add(new JLabel("  "));
    mainPanel.add(colorPanel);
    TimerListener timerListener = new TimerListener();
    timerListener.addColorChanger(new ColorChanger()
    {
      public void setColor(Color c)
      {
        label.setForeground(c);
        colorPanel.setBackground(c);
      }
    });
    new Timer(DELAY, timerListener).start();
    
  }
 
  private void initColors()
  {
    for (int i = 0; i < colors.length; i++)
    {
      int value = (int)(255 * (Math.cos(2 * Math.PI * (double)(i) / colors.length)+1)/2);
      colors[i] = new Color(value, GREEN_VALUE, 255 - value);
    }
  }
 
  private class TimerListener implements ActionListener
  {
    private int counter = 0;
    private List<ColorChanger> colorChangerList = new ArrayList<ColorChanger>();
    
    public void actionPerformed(ActionEvent e)
    {
      for (ColorChanger cc : colorChangerList)
      {
        cc.setColor(colors[counter]);
      }
      counter++;
      counter %= colors.length;
    }
    
    public void addColorChanger(ColorChanger cc)
    {
      colorChangerList.add(cc);
    }
  }
 
  // added to loosen coupling a little bit
  private interface ColorChanger
  {
    void setColor(Color c);
  }
  
  private static void createAndShowUI()
  {
    JFrame frame = new JFrame("Sine Wave Blink");
    frame.getContentPane().add(new PulsingColor().getMainPanel());
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
  }
 
  public static void main(String[] args)
  {
    java.awt.EventQueue.invokeLater(new Runnable()
    {
      public void run()
      {
        createAndShowUI();
      }
    });
  }
}

[ June 17, 2008: Message edited by: pete stein ]