Java Foundation Classes in a Nutshell

method of the Transferable object to actually transfer the data. This phase of

the data transfer is done exactly as it is in cut-and-paste. Finally, the compo-

nent calls the

dropComplete() method of the DropTargetDropEvent, passing

true if the transfer was successful or false if something went wrong and the

transfer did not succeed.

A Data Source

Example 6-2 shows the ColorSource class. This is a simple JComponent subclass

that displays a small block of a solid color and makes that color available for trans-

fer via both cut-and-paste and drag-and-drop. The

copy() method copies the color

to the clipboard, making it available for pasting, while the

dragGestureRecog-

nized()

method initiates a drag operation. This example relies upon the Trans-

ferableColor class of Example 6-1, of course. For simplicity, the copy() method is

invoked when the user clicks on the component—ther e is no Ctrl-C keyboard

binding or Edit menu command.

Example 6−2: ColorSour ce.java

import java.awt.*;

import java.awt.event.*;

import java.awt.datatransfer.*;

import java.awt.dnd.*;

import javax.swing.*;

import javax.swing.border.*;

import java.io.*;

/**

* This simple component displays a solid color and allows that color

*tobedragged. Also, it copies the color to the clipboard when the

* user clicks on it.

*/

public class ColorSource extends JComponent

implements ClipboardOwner, DragGestureListener, DragSourceListener

{

Color color; // ...