/*******************************************************************************
* Copyright (c) 2000, 2008 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 Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.swt.dnd;
/**
* <code>Transfer</code> provides a mechanism for converting between a java
* representation of data and a platform specific representation of data and
* vice versa. It is used in data transfer operations such as drag and drop and
* clipboard copy/paste.
* <p>
* You should only need to become familiar with this class if you are
* implementing a Transfer subclass and you are unable to subclass the
* ByteArrayTransfer class.
* </p>
*
* @see ByteArrayTransfer
* @since 1.3
*/
public abstract class Transfer {
/**
* Returns a list of the platform specific data types that can be converted
* using this transfer agent.
* <p>
* Only the data type fields of the <code>TransferData</code> objects are
* filled in.
* </p>
*
* @return a list of the data types that can be converted using this transfer
* agent
*/
abstract public TransferData[] getSupportedTypes();
/**
* Returns true if the <code>TransferData</code> data type can be converted
* using this transfer agent, or false otherwise (including if transferData is
* <code>null</code>).
*
* @param transferData a platform specific description of a data type; only
* the data type fields of the <code>TransferData</code> object need
* to be filled in
* @return true if the transferData data type can be converted using this
* transfer agent
*/
abstract public boolean isSupportedType( TransferData transferData );
/**
* Returns the platform specific ids of the data types that can be converted
* using this transfer agent.
*
* @return the platform specific ids of the data types that can be converted
* using this transfer agent
*/
abstract protected int[] getTypeIds();
/**
* Returns the platform specific names of the data types that can be converted
* using this transfer agent.
*
* @return the platform specific names of the data types that can be converted
* using this transfer agent.
*/
abstract protected String[] getTypeNames();
/**
* Converts a java representation of data to a platform specific
* representation of the data.
* <p>
* On a successful conversion, the transferData.result field will be set to
* 1.
* If this transfer agent is unable to perform the conversion, the
* transferData.result field will be set to a failure value of 0.
* </p>
*
* <p><strong>IMPORTANT:</strong> This method is <em>not</em> part of the RWT
* public API. It is marked public only so that it can be shared
* within the packages provided by RWT. It should never be accessed
* from application code.
* </p>
*
* @param object a java representation of the data to be converted; the type
* of Object that is passed in is dependent on the
* <code>Transfer</code> subclass.
* @param transferData an empty TransferData object; this object will be filled
* in on return with the platform specific representation of the data
* @exception org.eclipse.swt.SWTException <ul>
* <li>ERROR_INVALID_DATA - if object does not contain data in a
* valid format or is <code>null</code></li>
* </ul>
*/
// [rh] this method is declared as 'protected' in SWT. In RWT, it is declared
// public to be accessible from LCA code. Should be fixed in the future.
abstract public void javaToNative( Object object, TransferData transferData );
/**
* Converts a platform specific representation of data to a java
* representation.
*
* <p><strong>IMPORTANT:</strong> This method is <em>not</em> part of the RWT
* public API. It is marked public only so that it can be shared
* within the packages provided by RWT. It should never be accessed
* from application code.
* </p>
*
* @param transferData the platform specific representation of the data to be
* converted
* @return a java representation of the converted data if the conversion was
* successful; otherwise null. If transferData is <code>null</code>
* then <code>null</code> is returned. The type of Object that is
* returned is dependent on the <code>Transfer</code> subclass.
*/
// [rh] this method is declared as 'protected' in SWT. In RWT, it is declared
// public to be accessible from LCA code. Should be fixed in the future.
abstract public Object nativeToJava( TransferData transferData );
/**
* Registers a name for a data type and returns the associated unique
* identifier.
* <p>
* You may register the same type more than once, the same unique identifier
* will be returned if the type has been previously registered.
* </p>
*
* @param formatName the name of a data type
* @return the unique identifier associated with this data type
*/
public static int registerType( String formatName ) {
return formatName.hashCode();
}
/**
* Test that the object is of the correct format for this Transfer class.
*
* @param object a java representation of the data to be converted
* @return true if object is of the correct form for this transfer type
*/
protected boolean validate( Object object ) {
return true;
}
}