vaadin-framework/server/src/main/java/com/vaadin/event/dd/acceptcriteria/SourceIsTarget.java

/*
 * Copyright 2000-2016 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.acceptcriteria;

import com.vaadin.event.Transferable;
import com.vaadin.event.TransferableImpl;
import com.vaadin.event.dd.DragAndDropEvent;
import com.vaadin.event.dd.DropTarget;
import com.vaadin.ui.Component;

/**
 *
 * A criterion that ensures the drag source is the same as drop target. Eg.
 * {code Tree} or {@code Table} could support only re-ordering of items, but no
 * {@link Transferable}s coming outside.
 * <p>
 * Note! Class is singleton, use {@link #get()} method to get the instance.
 *
 * @since 6.3
 *
 */
public class SourceIsTarget extends ClientSideCriterion {

    private static final long serialVersionUID = -451399314705532584L;
    private static final SourceIsTarget instance = new SourceIsTarget();

    private SourceIsTarget() {
    }

    @Override
    public boolean accept(DragAndDropEvent dragEvent) {
        if (dragEvent.getTransferable() instanceof TransferableImpl) {
            Component sourceComponent = dragEvent.getTransferable()
                    .getSourceComponent();
            DropTarget target = dragEvent.getTargetDetails().getTarget();
            return sourceComponent == target;
        }
        return false;
    }

    public static synchronized SourceIsTarget get() {
        return instance;
    }

}