Creating a User Interface - Beginning J2ME: From Novice to Professional - page 62

Figure 5-6. Alerts are similar to modal dialog boxes in a desktop windowing system.
Alerts are represented by instances of the javax.microedition.lcdui.Alert class, which
offers the following constructors:
public Alert()
public Alert(String title, String alertText, Image alertImage, AlertType alertType)
Any or all of the parameters in the second constructor may be null . (Don't worry about the
Image class right now; we'll discuss it in the next chapter in the section on List s.)
By default, timed Alerts are created using a default timeout value; you can find out the
default value by calling getDefaultTimeout() . To change the Alert 's timeout, call setTimeout()
with the timeout value in milliseconds. A special value, FOREVER , may be used to indicate that
the Alert is modal.
You could create a simple timed Alert with the following code:
Alert alert = new Alert("Sorry", "I'm sorry, Dave...", null, null);
To explicitly set the timeout value to five seconds, you could do this:
alert.setTimeout(5000);
If, instead, you wanted a modal alert, you would use the special value FOREVER :
alert.setTimeout(Alert.FOREVER);
The MIDP implementation will automatically supply a way to dismiss a modal alert. Sun's
reference implementation, for example, provides a Done command mapped to a soft button.
This command is exposed as the static member DISMISS_COMMAND , allowing you to register your
own command listener and explicitly recognize this command. You can add your own commands
to an Alert using the usual addCommand() method. The first time you call addCommand() , the
system's Done command is removed.