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/*
* 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.event.dd;
import java.io.Serializable;
import com.vaadin.event.Transferable;
import com.vaadin.event.dd.acceptcriteria.AcceptAll;
import com.vaadin.event.dd.acceptcriteria.AcceptCriterion;
import com.vaadin.event.dd.acceptcriteria.ServerSideCriterion;
/**
* DropHandlers contain the actual business logic for drag and drop operations.
* <p>
* The {@link #drop(DragAndDropEvent)} method is used to receive the transferred
* data and the {@link #getAcceptCriterion()} method contains the (possibly
* client side verifiable) criterion whether the dragged data will be handled at
* all.
*
* @since 6.3
*
*/
public interface DropHandler extends Serializable {
/**
* Drop method is called when the end user has finished the drag operation
* on a {@link DropTarget} and {@link DragAndDropEvent} has passed
* {@link AcceptCriterion} defined by {@link #getAcceptCriterion()} method.
* The actual business logic of drag and drop operation is implemented into
* this method.
*
* @param event
* the event related to this drop
*/
public void drop(DragAndDropEvent event);
/**
* Returns the {@link AcceptCriterion} used to evaluate whether the
* {@link Transferable} will be handed over to
* {@link DropHandler#drop(DragAndDropEvent)} method. If client side can't
* verify the {@link AcceptCriterion}, the same criteria may be tested also
* prior to actual drop - during the drag operation.
* <p>
* Based on information from {@link AcceptCriterion} components may display
* some hints for the end user whether the drop will be accepted or not.
* <p>
* Vaadin contains a variety of criteria built in that can be composed to
* more complex criterion. If the build in criteria are not enough,
* developer can use a {@link ServerSideCriterion} or build own custom
* criterion with client side counterpart.
* <p>
* If developer wants to handle everything in the
* {@link #drop(DragAndDropEvent)} method, {@link AcceptAll} instance can be
* returned.
*
* @return the {@link AcceptCriterion}
*/
public AcceptCriterion getAcceptCriterion();
}
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