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Vaadin is a web application framework for Rich Internet Applications (RIA).
Vaadin enables easy development and maintenance of fast and
secure rich web
applications with a stunning look and feel and a wide browser support.
It features a server-side architecture with the majority of the logic
running
on the server. Ajax technology is used at the browser-side to ensure a
rich
and interactive user experience.
/*
* Copyright 2000-2014 Vaadin Ltd.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.vaadin.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;
import com.google.gwt.user.client.ui.Widget;
/**
* 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.
*
* Possible current registration is given as parameter. The returned
* registration (possibly the same as given, should be store for next update.
*
* Pseudocode what helpers do:
*
*
*
* 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
*
*
*
*
*/
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 if no handler has been
* registered previously
* @return a new registration handler that can be used to unregister the
* handler later
*/
public static HandlerRegistration updateFocusHandler(
T connector, HandlerRegistration handlerRegistration) {
return updateHandler(connector, FOCUS, handlerRegistration,
FocusEvent.getType(), connector.getWidget());
}
/**
* 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 if no handler has been
* registered previously
* @param widget
* The widget which emits focus events
* @return a new registration handler that can be used to unregister the
* handler later
*/
public static HandlerRegistration updateFocusHandler(
T connector, HandlerRegistration handlerRegistration, Widget widget) {
return updateHandler(connector, FOCUS, handlerRegistration,
FocusEvent.getType(), widget);
}
/**
* 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 if no handler has been
* registered previously
* @return a new registration handler that can be used to unregister the
* handler later
*/
public static HandlerRegistration updateBlurHandler(
T connector, HandlerRegistration handlerRegistration) {
return updateHandler(connector, BLUR, handlerRegistration,
BlurEvent.getType(), connector.getWidget());
}
/**
* 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 if no handler has been
* registered previously
* @param widget
* The widget which emits blur events
*
* @return a new registration handler that can be used to unregister the
* handler later
*/
public static HandlerRegistration updateBlurHandler(
T connector, HandlerRegistration handlerRegistration, Widget widget) {
return updateHandler(connector, BLUR, handlerRegistration,
BlurEvent.getType(), widget);
}
private static HandlerRegistration updateHandler(
ComponentConnector connector, String eventIdentifier,
HandlerRegistration handlerRegistration, Type type, Widget widget) {
if (connector.hasEventListener(eventIdentifier)) {
if (handlerRegistration == null) {
handlerRegistration = widget.addDomHandler((H) connector, type);
}
} else if (handlerRegistration != null) {
handlerRegistration.removeHandler();
handlerRegistration = null;
}
return handlerRegistration;
}
}