Ajax? No problem.
If the page is only redisplayed due to error then try this:
void onPrepareForRender() {
// If fresh start, populate screen with initial values
if (form.isValid()) {
// Do init here...
}
}
However, if the page is being redisplayed even when there are no errors, add a
hidden field, say "inited", to the form:
private boolean inited;
void onPrepareForRender() {
// If not initialised, populate screen with initial values
if (!inited) {
// Do init here…
// Then at the end…
inited = true;
}
}
"Inited" won't reset to false until you do a page render request or explicitly
set it to false.
I've successfully used this approach in the AjaxFormLoop examples, e.g.
http://jumpstart.doublenegative.com.au/jumpstart/examples/ajax/formloop1
Cheers,
Geoff
On 05/05/2012, at 1:31 AM, Norman Franke wrote:
> On May 4, 2012, at 8:53 AM, Arno Haase wrote:
>
>>>> onPrepare() is called before data binding, but it is called
>>>> again after data binding. So simple initialization code in
>>>> onPrepare() would overwrite the form data with the default.
>>>
>>> This isn't correct. It's called once per request. And Tapestry
>>> uses redirect-after-post, so the form submission and the form
>>> rendering are never in the same request (unless you're doing the
>>> submission though AJAX).
>>
>> Thanks for pointing this out.
>>
>> But since I am using AJAX - does anyone have a recommendation for
>> where to put the initializations?
>
>
> Good question. I never came up with a good solution, either, without having
> two events. One can do onActivate(), but if you are doing something slow,
> like reading values from a database, I wouldn't recommend it. This is because
> onActivate is called to construct the URL in any referencing page. As a
> result, my start page calls onActivate for like 30 pages and is very slow on
> startup.
>
> @SetupRender is another potential place, but I don't think it's called for
> AJAX, so I often just call it from my AJAX listener. Seems we really need an
> @OnInitGoesHere or something. :)
>
> Norman Franke
> Answering Service for Directors, Inc.
> www.myasd.com
>
>
>
