com.google.gwt.event.logical.shared.SelectionEvent.java Source code

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Here is the source code for com.google.gwt.event.logical.shared.SelectionEvent.java

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/*
 * Copyright 2008 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.event.logical.shared;

import com.google.gwt.event.shared.GwtEvent;

/**
 * Represents a selection event.
 * 
 * @param <T> the type being selected
 */
public class SelectionEvent<T> extends GwtEvent<SelectionHandler<T>> {

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

    /**
     * Fires a selection event on all registered handlers in the handler
     * manager.If no such handlers exist, this method will do nothing.
     * 
     * @param <T> the selected item type
     * @param source the source of the handlers
     * @param selectedItem the selected item
     */
    public static <T> void fire(HasSelectionHandlers<T> source, T selectedItem) {
        if (TYPE != null) {
            SelectionEvent<T> event = new SelectionEvent<T>(selectedItem);
            source.fireEvent(event);
        }
    }

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

    private final T selectedItem;

    /**
     * Creates a new selection event.
     * 
     * @param selectedItem selected item
     */
    protected SelectionEvent(T selectedItem) {
        this.selectedItem = selectedItem;
    }

    // The instance knows its BeforeSelectionHandler is of type I, but the TYPE
    // field itself does not, so we have to do an unsafe cast here.
    @SuppressWarnings("unchecked")
    @Override
    public final Type<SelectionHandler<T>> getAssociatedType() {
        return (Type) TYPE;
    }

    /**
     * Gets the selected item.
     * 
     * @return the selected item
     */
    public T getSelectedItem() {
        return selectedItem;
    }

    @Override
    protected void dispatch(SelectionHandler<T> handler) {
        handler.onSelection(this);
    }
}