Color Drag Source
/*
* This example is from the book "Java Foundation Classes in a Nutshell".
* Written by David Flanagan. Copyright (c) 1999 by O'Reilly & Associates.
* You may distribute this source code for non-commercial purposes only.
* You may study, modify, and use this example for any purpose, as long as
* this notice is retained. Note that this example is provided "as is",
* WITHOUT WARRANTY of any kind either expressed or implied.
*/
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
* to be dragged. 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; // The color to display
TransferableColor tcolor; // The color, encapsulated for data transfer
DragSource dragSource; // We need this object for drag-and-drop
/** A ColorSource normally displays itself with this border */
protected static Border defaultBorder = new BevelBorder(BevelBorder.LOWERED);
/** When we are the clipboard owner, uses this border */
protected static Border highlightBorder =
new CompoundBorder(defaultBorder, new LineBorder(Color.black, 2));
/** Create a new ColorSource object that displays the speciifed color */
public ColorSource(Color color) {
// Save the color. Encapsulate it in a Transferable object so that
// it can be used with cut-and-paste and drag-and-drop
this.color = color;
this.tcolor = new TransferableColor(color);
// Set our default border
this.setBorder(defaultBorder);
// Listen for mouse clicks, and copy the color to the clipboard.
this.addMouseListener(new MouseAdapter() {
public void mouseClicked(MouseEvent e) { copy(); }
});
// Set up a DragGestureRecognizer that will detect when the user
// begins a drag. When it detects one, it will notify us by calling
// the dragGestureRecognized() method of the DragGestureListener
// interface we implement below
this.dragSource = DragSource.getDefaultDragSource();
dragSource.createDefaultDragGestureRecognizer(this, // Look for drags on us
DnDConstants.ACTION_COPY_OR_MOVE, // Recognize these types
this); // Tell us when recognized
}
// These are component methods that make this class work as a component.
// They specify how big the component is, and what it it looks like.
protected static Dimension mysize = new Dimension(25, 25);
public Dimension getMinimumSize() { return mysize; }
public Dimension getPreferredSize() { return mysize; }
public void paintComponent(Graphics g) {
g.setColor(color);
Dimension s = this.getSize();
Insets i = this.getInsets();
g.fillRect(i.left, i.top,
s.width-i.left-i.right, s.height-i.top-i.bottom);
}
// The methods below support cut-and-paste
/** This method copies the color to the clipboard. */
public void copy() {
// Get system clipboard
Clipboard c = this.getToolkit().getSystemClipboard();
// Put our TransferableColor object on the clipboard.
// Also, we'll get notification when we no longer own the clipboard
c.setContents(tcolor, this);
// Set a special border on ourselves that indicates that we're the
// current color available for pasting.
this.setBorder(highlightBorder);
}
// This ClipboardOwner method is called when something else is
// placed on the clipboard. It means that our color is no longer
// available for pasting, and we should not display the highlight border
public void lostOwnership(Clipboard clipboard, Transferable contents) {
this.setBorder(defaultBorder);
}
// The methods below support drag-and-drop
// This DragGestureListener method is called when the DragGestureRecognizer
// detects that the user has dragged the mouse. It is responsible
// for beginning the drag-and-drop process.
public void dragGestureRecognized(DragGestureEvent e) {
// Create an image we can drag along with us.
// Not all systems support this, but it doesn't hurt to try.
Image colorblock = this.createImage(25,25);
Graphics g = colorblock.getGraphics();
g.setColor(color);
g.fillRect(0,0,25,25);
// Start dragging our transferable color object.
e.startDrag(DragSource.DefaultMoveDrop, // The initial drag cursor
colorblock, new Point(0,0), // The image to drag
tcolor, // The data being dragged
this); // Who to notify during drag
}
// These methods implement DragSourceListener.
// Since we passed this object to startDrag, these methods will be
// called at interesting points during the drag. We could use them,
// for example to implement custom cursors or other "drag over" effects
public void dragEnter(DragSourceDragEvent e) {}
public void dragExit(DragSourceEvent e) {}
public void dragDropEnd(DragSourceDropEvent e) {}
public void dragOver(DragSourceDragEvent e) {}
public void dropActionChanged(DragSourceDragEvent e) {}
}
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