Detect browser back or forward button clicked

[Anita]

Hi,

How can I detect on GWT client side that browser's back or forward
button is clicked? Because on click of back and forward button i want
to perform custom operation.

Thank You.

[Tercio]

You can't.

What you can is handle history changes, that occurs when user push
back and forward in the browser, but only works for links in the same
page(#anchor).

public class Dummy implements ValueChangeHandler<String>
{
public Dummy()
{
// Register ourselves with the History API.
History.addValueChangeHandler(this);
}

public void onValueChange(ValueChangeEvent<String> event)
{
// User has clicked back or forward, the event parameter has the
value itself.
}
}

Regards,

[Anita]

Hi Tercio,

thanks for the quick reply. Is it possible that i can get it from DOM
or from javascript native code.

[Rogério Valente]

I don't know if this can help you but, we just add a script in
<appName>.html to disable some functions key (F5 to refresh).
Take a look at the code below. Put it in a javascript file in
<appName>/war/js and add a script tag on the head section of your app
main html file ..
something like <script type="text/javascript" language="javascript"
src="js/disableFunctionKey.js"></script>

Maybe you can find a solution to disable the buttons.

[CODE]

//Disable F5 - Refresh
var isIE = ( navigator.userAgent.toLowerCase().indexOf("msie") !=
-1 );
function interceptKeyDown(e) {
keyCode = e.keyCode;
//F5
if ( keyCode == 116 ) {
if(isIE) {
// IE only
e.keyCode = 505;
}
return false;
}
}
function interceptKeyPress(e) {
if( !e ) {
if (window.event)
e = window.event;
else
return;
}
//NS 4, NS 6+, Mozilla 0.9+, Opera
if(typeof(e.which) == 'number') {
var keyCode = e.keyCode ? e.keyCode : e.which ? e.which :
void 0;
if(e.charCode == null || e.charCode == 0 ) {
// F5
if ( keyCode == 116 ) {
e.stopPropagation();
e.preventDefault();
}
}
}
}
function attachEventListener( obj, type, func, capture ) {
if(window.addEventListener) {
//Mozilla, Netscape, Firefox
obj.addEventListener( type, func, capture );
} else {
//IE
obj.attachEvent( 'on' + type, func );
}
}

attachEventListener(document,"keydown",interceptKeyDown,true);
attachEventListener(document,"keypress",interceptKeyPress,true);

[END-CODE]

[Anita]

Hi Rogério Valente,

Thanks for the reply.
If i disable the buttons how will i come to know that the back button
is clicked ?

[Rogério Valente]

Well, in fact you don't "disable" the buttons.
In the disableFunctionKey.js file, the function just intercept the
keydown or keypress
and return a value tha is not the expected by the browser.

As I wrote, maybe you can find a solution that intercept the browser
back button click.