org.eclipse.emf.edit.ui.dnd.LocalTransfer Maven / Gradle / Ivy
/**
*
*
* Copyright (c) 2002-2004 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM - Initial API and implementation
*
*
*
* $Id: LocalTransfer.java,v 1.2 2005/06/08 06:20:52 nickb Exp $
*/
package org.eclipse.emf.edit.ui.dnd;
import org.eclipse.swt.dnd.ByteArrayTransfer;
import org.eclipse.swt.dnd.TransferData;
/**
* This derived implementation of a byte array transfer short circuits the transfer process
* so that a local transfer does not serialize the object
* and hence can and will return the original object, not just a clone.
* You only really need ever know about {@link #getInstance LocalTransfer.getInstance()},
* so that you can include it in when adding drag support to a viewer.
* See {@link EditingDomainViewerDropAdapter} and {@link ViewerDragAdapter} for more details.
*
* As an addded guard, the time is recorded and serialized in javaToNative
* to that navive to java can ensure that it's returns the value that was really to have been transferred.
*/
public class LocalTransfer extends ByteArrayTransfer
{
/**
* This is the register transfer type name.
*/
protected static final String TYPE_NAME = "local-transfer-format";
/**
* This is the ID that is registered to the name.
*/
protected static final int TYPE_ID = registerType(TYPE_NAME);
/**
* This is initialized and returned by {@link #getInstance}.
*/
protected static LocalTransfer instance;
/**
* This returns the one instance of this transfer agent.
*/
public static LocalTransfer getInstance()
{
if (instance == null)
{
instance = new LocalTransfer();
}
return instance;
}
/**
* This records the time at which the transfer data was recorded.
*/
protected long startTime;
/**
* This records the data being transferred.
*/
protected Object object;
/**
* This creates an instance; typically you get one from {@link #getInstance}.
*/
protected LocalTransfer()
{
}
/**
* This returns the transfer ids that this agent supports.
*/
protected int[] getTypeIds()
{
return new int[] { TYPE_ID };
}
/**
* This returns the transfer names that this agent supports.
*/
public String[] getTypeNames()
{
return new String[] { TYPE_NAME };
}
/**
* This records the object and current time and encodes only the current time into the transfer data.
*/
public void javaToNative(Object object, TransferData transferData)
{
startTime = System.currentTimeMillis();
this.object = object;
if (transferData != null)
{
super.javaToNative(String.valueOf(startTime).getBytes(), transferData);
}
}
/**
* This decodes the time of the transfer and returns the recorded the object if the recorded time and the decoded time match.
*/
public Object nativeToJava(TransferData transferData)
{
byte[] bytes = (byte[])super.nativeToJava(transferData);
if (bytes == null) return null;
try
{
long startTime = Long.valueOf(new String(bytes)).longValue();
return this.startTime == startTime ? object : null;
}
catch (NumberFormatException exception)
{
return null;
}
}
}