16.1. Displaying Messages
on the Screen of Wireless Devices: alert() Function
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:
 Sony
Ericsson T68i
|
 Nokia
Mobile Browser 4.0
|
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:
 Sony
Ericsson T68i
|
 Nokia
Mobile Browser 4.0
|
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:
 Sony
Ericsson T68i
|
 Nokia
Mobile Browser 4.0
|
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