From Forum Nokia Wiki

ID	CS000957	Creation date	May 14, 2008
Platform	S60 3rd Edition, MR S60 3rd Edition, FP1	Tested on devices	Nokia E61i Nokia N95 8GB
Category	Java ME	Subcategory	Hardware

Keywords (APIs, classes, methods, functions): javax.microedition.lcdui.Display, javax.microedition.lcdui.Display.flashBacklight()

Overview

This snippet demonstrates how to flash the backlight of the device for a specified duration. In practice, the MIDlet constructs a menu item through which the user can flash the backlight.

Source

Flashing the backlight can be implemented as follows:

// Flash the backlight for 5 seconds
Display.getDisplay(this).flashBacklight(5000);

Here is a complete example:

import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.midlet.MIDlet;

public class ExampleMIDlet extends MIDlet implements CommandListener {
    private Command flashCommand;
    private Command exitCommand;
    private Form mainForm;
 
    /**
     * Constructor. Constructs the object and initializes displayables.
     */
    public ExampleMIDlet() {
        mainForm = new Form("ExampleMIDlet");
 
        flashCommand = new Command("Flash", Command.SCREEN, 0);
        mainForm.addCommand(flashCommand);
 
        exitCommand = new Command("Exit", Command.EXIT, 0);
        mainForm.addCommand(exitCommand);
 
        mainForm.setCommandListener(this);
    }
 
    /**
     * Called when the MIDlet is started.
     */
    public void startApp() {
        Display.getDisplay(this).setCurrent(mainForm);
    }
 
    // Other inherited methods omitted for brevity
    // ...
 
    /**
     * From CommandListener.
     * Called by the system to indicate that a command has been invoked on a
     * particular displayable.
     * @param command the command that was invoked
     * @param displayable the displayable where the command was invoked
     */
    public void commandAction(Command command, Displayable displayable) {
        if (command == flashCommand) {
            // Flash the backlight for 5 seconds
            boolean flashAllowed = Display.getDisplay(this).flashBacklight(5000);
            if (!flashAllowed) {
                // TODO: Flashing is not allowed. Inform the user.
            }
        } else if (command == exitCommand) {
            // Exit the MIDlet
            destroyApp(true);
            notifyDestroyed();
        }
    }

Postconditions

If the user selects the Flash menu item, the backlight is flashed for 5 seconds.