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/*
@VaadinApache2LicenseForJavaFiles@
*/
package com.vaadin.terminal.gwt.client;
import static com.vaadin.shared.EventId.BLUR;
import static com.vaadin.shared.EventId.FOCUS;
import com.google.gwt.event.dom.client.BlurEvent;
import com.google.gwt.event.dom.client.BlurHandler;
import com.google.gwt.event.dom.client.DomEvent.Type;
import com.google.gwt.event.dom.client.FocusEvent;
import com.google.gwt.event.dom.client.FocusHandler;
import com.google.gwt.event.shared.EventHandler;
import com.google.gwt.event.shared.HandlerRegistration;
/**
* Helper class for attaching/detaching handlers for Vaadin client side
* components, based on identifiers in UIDL. Helpers expect Paintables to be
* both listeners and sources for events. This helper cannot be used for more
* complex widgets.
* <p>
* Possible current registration is given as parameter. The returned
* registration (possibly the same as given, should be store for next update.
* <p>
* Pseudocode what helpers do:
*
* <pre>
*
* if paintable has event listener in UIDL
* if registration is null
* register paintable as as handler for event
* return the registration
* else
* if registration is not null
* remove the handler from paintable
* return null
*
*
* </pre>
*
*/
public class EventHelper {
/**
* Adds or removes a focus handler depending on if the connector has focus
* listeners on the server side or not.
*
* @param connector
* The connector to update. Must implement focusHandler.
* @param handlerRegistration
* The old registration reference or null no handler has been
* registered previously
* @return a new registration handler that can be used to unregister the
* handler later
*/
public static <T extends ComponentConnector & FocusHandler> HandlerRegistration updateFocusHandler(
T connector, HandlerRegistration handlerRegistration) {
return updateHandler(connector, FOCUS, handlerRegistration,
FocusEvent.getType());
}
/**
* Adds or removes a blur handler depending on if the connector has blur
* listeners on the server side or not.
*
* @param connector
* The connector to update. Must implement BlurHandler.
* @param handlerRegistration
* The old registration reference or null no handler has been
* registered previously
* @return a new registration handler that can be used to unregister the
* handler later
*/
public static <T extends ComponentConnector & BlurHandler> HandlerRegistration updateBlurHandler(
T connector, HandlerRegistration handlerRegistration) {
return updateHandler(connector, BLUR, handlerRegistration,
BlurEvent.getType());
}
private static <H extends EventHandler> HandlerRegistration updateHandler(
ComponentConnector connector, String eventIdentifier,
HandlerRegistration handlerRegistration, Type<H> type) {
if (connector.hasEventListener(eventIdentifier)) {
if (handlerRegistration == null) {
handlerRegistration = connector.getWidget().addDomHandler(
(H) connector, type);
}
} else if (handlerRegistration != null) {
handlerRegistration.removeHandler();
handlerRegistration = null;
}
return handlerRegistration;
}
}
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