Snippet79.java

/*******************************************************************************
 * Copyright (c) 2000, 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 Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.swt.snippets;

/*
 * Drag and Drop example snippet: define my own data transfer type
 *
 * For a list of all SWT example snippets see
 * http://www.eclipse.org/swt/snippets/
 * 
 * @since 3.1
 */
import java.io.*;

import org.eclipse.swt.*;
import org.eclipse.swt.dnd.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;

public class Snippet79 {

/* The data being transferred is an <bold>array of type MyType</bold> where MyType is define as: */
static class MyType {
	String fileName;
	long fileLength;
	long lastModified;
}

static class MyTransfer extends ByteArrayTransfer {

	private static final String MYTYPENAME = "name_for_my_type";
	private static final int MYTYPEID = registerType (MYTYPENAME);
	private static MyTransfer _instance = new MyTransfer ();

public static MyTransfer getInstance () {
	return _instance;
}

@Override
public void javaToNative (Object object, TransferData transferData) {
	if (!checkMyType(object) || !isSupportedType (transferData)) {
		DND.error(DND.ERROR_INVALID_DATA);
	}
	MyType [] myTypes = (MyType []) object;
	try {
		// write data to a byte array and then ask super to convert to pMedium
		ByteArrayOutputStream out = new ByteArrayOutputStream ();
		DataOutputStream writeOut = new DataOutputStream (out);
		for (int i = 0, length = myTypes.length; i < length; i++) {
			byte [] buffer = myTypes [i].fileName.getBytes ();
			writeOut.writeInt (buffer.length);
			writeOut.write (buffer);
			writeOut.writeLong (myTypes [i].fileLength);
			writeOut.writeLong (myTypes [i].lastModified);
		}
		byte [] buffer = out.toByteArray ();
		writeOut.close ();
		super.javaToNative (buffer, transferData);
	}
	catch (IOException e) {}
}

@Override
public Object nativeToJava (TransferData transferData) {
	if (isSupportedType (transferData)) {
		byte [] buffer = (byte []) super.nativeToJava (transferData);
		if (buffer == null) return null;

		MyType [] myData = new MyType [0];
		try {
			ByteArrayInputStream in = new ByteArrayInputStream (buffer);
			DataInputStream readIn = new DataInputStream (in);
			while (readIn.available () > 20) {
				MyType datum = new MyType ();
				int size = readIn.readInt ();
				byte [] name = new byte [size];
				readIn.read (name);
				datum.fileName = new String (name);
				datum.fileLength = readIn.readLong ();
				datum.lastModified = readIn.readLong ();
				MyType [] newMyData = new MyType [myData.length + 1];
				System.arraycopy (myData, 0, newMyData, 0, myData.length);
				newMyData [myData.length] = datum;
				myData = newMyData;
			}
			readIn.close ();
		}
		catch (IOException ex) {
			return null;
		}
		return myData;
	}

	return null;
}

@Override
protected String [] getTypeNames () {
	return new String [] {MYTYPENAME};
}

@Override
protected int [] getTypeIds () {
	return new int [] {MYTYPEID};
}

boolean checkMyType(Object object) {
	if (object == null || 
		!(object instanceof MyType[]) || 
		((MyType[])object).length == 0) {
		return false;
	}
	MyType[] myTypes = (MyType[])object;
	for (int i = 0; i < myTypes.length; i++) {
		if (myTypes[i] == null || 
			myTypes[i].fileName == null || 
			myTypes[i].fileName.length() == 0) {
			return false;
		}
	}
	return true;
}

@Override
protected boolean validate(Object object) {
	return checkMyType(object);
}
}

public static void main (String [] args) {
	Display display = new Display ();
	Shell shell = new Shell (display);
	shell.setLayout (new FillLayout ());
	final Label label1 = new Label (shell, SWT.BORDER | SWT.WRAP);
	label1.setText ("Drag Source for MyData[]");
	final Label label2 = new Label (shell, SWT.BORDER | SWT.WRAP);
	label2.setText ("Drop Target for MyData[]");

	DragSource source = new DragSource (label1, DND.DROP_COPY);
	source.setTransfer (new Transfer [] {MyTransfer.getInstance ()});
	source.addDragListener (new DragSourceAdapter () {
		@Override
		public void dragSetData (DragSourceEvent event) {
			MyType myType1 = new MyType ();
			myType1.fileName = "C:\\abc.txt";
			myType1.fileLength = 1000;
			myType1.lastModified = 12312313;
			MyType myType2 = new MyType ();
			myType2.fileName = "C:\\xyz.txt";
			myType2.fileLength = 500;
			myType2.lastModified = 12312323;
			event.data = new MyType [] {myType1, myType2};
		}
	});
	DropTarget target = new DropTarget (label2, DND.DROP_COPY | DND.DROP_DEFAULT);
	target.setTransfer (new Transfer [] {MyTransfer.getInstance ()});
	target.addDropListener (new DropTargetAdapter () {
		@Override
		public void dragEnter (DropTargetEvent event) {
			if (event.detail == DND.DROP_DEFAULT) {
				event.detail = DND.DROP_COPY;
			}
		}

		@Override
		public void dragOperationChanged (DropTargetEvent event) {
			if (event.detail == DND.DROP_DEFAULT) {
				event.detail = DND.DROP_COPY;
			}
		}

		@Override
		public void drop (DropTargetEvent event) {
			if (event.data != null) {
				MyType [] myTypes = (MyType []) event.data;
				if (myTypes != null) {
					String string = "";
					for (int i = 0; i < myTypes.length; i++) {
						string += myTypes [i].fileName + " ";
					}
					label2.setText (string);
				}
			}
		}

	});
	shell.setSize (200, 200);
	shell.open ();
	while (!shell.isDisposed ()) {
		if (!display.readAndDispatch ()) display.sleep ();
	}
	display.dispose ();
}
}