Ideally, I would want to add a small wait period after each key stroke before
the event is actually triggered and throttle the last event if another one
comes in before the time period expires.
Antti Mattila wrote:
>
> Problem:
> I want to validate input as user types it, but validation takes a long
> time
> on the server. When validation result for the first input is returned,
> user
> might have caused several more input events to be validated. These
> validation requests are pending execution on Wicket Ajax Channel. At this
> point I'm only interested in validating the latest input, but before this
> happens, all pending validation requests are processed. This is
> unnecessary
> and takes a lot of time so I want to cancel all the pending requests.
>
> Solution:
> I did this by using named Channel and clearing all pending requests before
> requesting the latest validation. I couldn't find a solution for this
> problem, so I'm posting it here. Hopefully this might help someone else
> and
> please give me some feedback if this solution was not a good one.
>
> Thanks,
> Antti Mattila
>
> Here's the code:
>
> public class ClearPendingAjaxRequests extends AjaxCallDecorator {
> private final String clearPendingRequestsScript;
>
> public ClearPendingAjaxRequests(final String channel) {
> clearPendingRequestsScript = "if (typeof
> Wicket.channelManager.channels['" + channel + "'] != 'undefined')
> Wicket.channelManager.channels['" + channel + "'].callbacks = new
> Array();";
> }
>
> @Override
> public CharSequence decorateScript(final CharSequence script) {
> return clearPendingRequestsScript + script;
> }
> }
>
> public class UsersInputFieldOnChangeAjaxBehavior extends
> AjaxFormComponentUpdatingBehavior {
> public UsersInputFieldOnChangeAjaxBehavior() {
> super("onkeyup");
> setThrottleDelay(Duration.milliseconds(500));
> }
>
> @Override
> protected IAjaxCallDecorator getAjaxCallDecorator() {
> return new ClearPendingAjaxRequests(getChannelName());
> }
>
> @Override
> protected String getChannelName() {
> return "ChannelForValidatingThisSpecificInput";
> }
>
> @Override
> protected void onUpdate(final AjaxRequestTarget target) {
> // Validate user's input, this takes a long time.
> // Update UI.
> }
> }
>
>
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