com.google.gwt.event.logical.shared.BeforeSelectionEvent Maven / Gradle / Ivy
/*
* 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 before selection event.
*
* @param the type about to be selected
*/
public class BeforeSelectionEvent extends
GwtEvent> {
/**
* Handler type.
*/
private static Type> TYPE;
/**
* Fires a before selection event on all registered handlers in the handler
* manager. If no such handlers exist, this method will do nothing.
*
* @param the item type
* @param source the source of the handlers
* @param item the item
* @return the event so that the caller can check if it was canceled, or null
* if no handlers of this event type have been registered
*/
public static BeforeSelectionEvent fire(
HasBeforeSelectionHandlers source, T item) {
// If no handlers exist, then type can be null.
if (TYPE != null) {
BeforeSelectionEvent event = new BeforeSelectionEvent();
event.setItem(item);
source.fireEvent(event);
return event;
}
return null;
}
/**
* Gets the type associated with this event.
*
* @return returns the handler type
*/
public static Type> getType() {
if (TYPE == null) {
TYPE = new Type>();
}
return TYPE;
}
private T item;
private boolean canceled;
/**
* Creates a new before selection event.
*/
protected BeforeSelectionEvent() {
}
/**
* Cancel the before selection event.
*
* Classes overriding this method should still call super.cancel().
*/
public void cancel() {
canceled = true;
}
// 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> getAssociatedType() {
return (Type) TYPE;
}
/**
* Gets the item.
*
* @return the item
*/
public T getItem() {
return item;
}
/**
* Has the selection event already been canceled?
*
* @return is canceled
*/
public boolean isCanceled() {
return canceled;
}
@Override
protected void dispatch(BeforeSelectionHandler handler) {
handler.onBeforeSelection(this);
}
/**
* Sets the item.
*
* @param item the item
*/
protected final void setItem(T item) {
this.item = item;
}
}