Exceptions - Java Software Solutions: Foundations of Program Design - page 561

LISTING 11.9 continued

public LightBulbPanel()
{
lightOn = new ImageIcon ("lightBulbOn.gif");
lightOff = new ImageIcon ("lightBulbOff.gif");

setBackground (Color.black);

on = true ;
imageLabel = new JLabel (lightOff);
add (imageLabel);
}

//-----------------------------------------------------------------
// Paints the panel using the appropriate image.
//-----------------------------------------------------------------
public void paintComponent (Graphics page)
{
super .paintComponent(page);

if (on)
imageLabel.setIcon (lightOn);
else
imageLabel.setIcon (lightOff);
}

//-----------------------------------------------------------------
// Sets the status of the light bulb.
//-----------------------------------------------------------------
public void setOn ( boolean lightBulbOn)
{
on = lightBulbOn;
}
}

The LightBulbControls class shown in Listing 11.10 is a panel that contains
the on and off buttons. Both of these buttons have tool tips assigned to them,
and both use mnemonics. Also, when one of the buttons is enabled, the other is
disabled, and vice versa. When the light bulb is on, there is no reason for the On
button to be enabled. Likewise, when the light bulb is off, there is no reason for
the Off button to be enabled.

VideoNote

Exploring GUI
design details.