com.google.gwt.view.client.SelectionChangeEvent.java Source code

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Here is the source code for com.google.gwt.view.client.SelectionChangeEvent.java

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/*
 * Copyright 2010 Google Inc.
 * 
 * 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.google.gwt.view.client;

import com.google.gwt.event.shared.EventHandler;
import com.google.gwt.event.shared.GwtEvent;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.event.shared.HasHandlers;

/**
 * Represents a selection change event.
 */
public class SelectionChangeEvent extends GwtEvent<SelectionChangeEvent.Handler> {

    /**
     * Handler interface for {@link SelectionChangeEvent} events.
     */
    public static interface Handler extends EventHandler {

        /**
         * Called when a {@link SelectionChangeEvent} is fired.
         *
         * @param event the {@link SelectionChangeEvent} that was fired
         */
        void onSelectionChange(SelectionChangeEvent event);
    }

    /**
     * Interface specifying that a class can add
     * {@code SelectionChangeEvent.Handler}s.
     */
    public interface HasSelectionChangedHandlers extends HasHandlers {
        /**
         * Adds a {@link SelectionChangeEvent} handler.
         * 
         * @param handler the handler
         * @return {@link HandlerRegistration} used to remove this handler
         */
        HandlerRegistration addSelectionChangeHandler(Handler handler);
    }

    /**
     * Handler type.
     */
    private static Type<SelectionChangeEvent.Handler> TYPE;

    /**
     * Fires a selection change event on all registered handlers in the handler
     * manager. If no such handlers exist, this method will do nothing.
     *
     * @param source the source of the handlers
     */
    public static void fire(HasSelectionChangedHandlers source) {
        if (TYPE != null) {
            SelectionChangeEvent event = new SelectionChangeEvent();
            source.fireEvent(event);
        }
    }

    /**
     * Gets the type associated with this event.
     *
     * @return returns the handler type
     */
    public static Type<SelectionChangeEvent.Handler> getType() {
        if (TYPE == null) {
            TYPE = new Type<SelectionChangeEvent.Handler>();
        }
        return TYPE;
    }

    /**
     * Creates a selection change event.
     */
    SelectionChangeEvent() {
    }

    @Override
    public final Type<SelectionChangeEvent.Handler> getAssociatedType() {
        return TYPE;
    }

    @Override
    protected void dispatch(SelectionChangeEvent.Handler handler) {
        handler.onSelectionChange(this);
    }
}