16.1. Displaying Messages on the Screen of Wireless Devices: alert() Function

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The alert() function of the Dialogs standard library is used to display a message on the screen of a wireless device. The WML browser goes back to the original card when the user confirms he/she has read it. Its syntax is like this:

Dialogs.alert(message);

message is the message to be displayed. The alert() function returns an empty string if everything works fine. It returns an invalid value if errors occur.

The following WML/WMLScript example illustrates how to use the alert() function:

(alertEg1.wml)

<?xml version="1.0"?>
<!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.3//EN" "http://www.wapforum.org/DTD/wml13.dtd">

<wml>
  <card id="card1" title="alert() Example">
    <p>
      Enter a number between 1-100:<br/>
      <input name="number"/><br/><br/>
      <a href="alertEg1.wmls#checkRange($(number))">Continue</a>
    </p>
  </card>

  <card id="card2" title="alert() Example">
    <p>
      The number you entered is $(number).
    </p>
  </card>
</wml>

(alertEg1.wmls)

extern function checkRange(number)
{
  if (number < 1)
    Dialogs.alert("Number too small. Please enter again.");
  else if (number > 100)
    Dialogs.alert("Number too large. Please enter again.");
  else
    WMLBrowser.go("#card2");
}

The following screenshots show what you will see if you open the WML document of the above example in some mobile phone browsers:

If you enter 999 in the input field and click the "Continue" anchor link, a warning message is given informing you that the number is too large:

Click the "Yes" button of the Sony Ericsson T68i emulator or the "OK" softkey of the Nokia Mobile Browser 4.0 to go back to the original card:

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