/*
* Copyright (c) 2004 David Flanagan. All rights reserved.
* This code is from the book Java Examples in a Nutshell, 3nd Edition.
* It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
* You may study, use, and modify it for any non-commercial purpose,
* including teaching and use in open-source projects.
* You may distribute it non-commercially as long as you retain this notice.
* For a commercial use license, or to purchase the book,
* please visit http://www.davidflanagan.com/javaexamples3.
*/
package je3.datatransfer;
import java.awt.*; // Graphics, Rectangle, Stroke, etc.
import java.awt.datatransfer.*; // Transferable, DataFlavor
import java.awt.dnd.*; // Drag-and-drop listeners and events
import java.awt.event.*; // Mouse events
import javax.swing.*; // JComponent
import javax.swing.border.*; // LineBorder and BevelBorder
import java.util.*; // ArrayList, etc.
import java.util.List; // Explicit import to disambiguate from java.awt.List
import je3.graphics.PolyLine; // The Shape of scribbles
/**
* This rewrite of ScribblePane allows individual PolyLine lines to be
* selected, cut, copied, pasted, dragged, and dropped.
*/
public class TransferableScribblePane extends JComponent {
List lines; // The PolyLines that comprise this scribble
PolyLine currentLine; // The line currently being drawn
PolyLine selectedLine; // The line that is current selected
boolean canDragImage; // Can we drag an image of the line?
// Lines are 3 pixels wide, and the selected line is drawn dashed
static Stroke stroke = new BasicStroke(3.0f);
static Stroke selectedStroke = new BasicStroke(3, BasicStroke.CAP_BUTT,
BasicStroke.JOIN_ROUND, 0f,
new float[] { 3f, 3f, },0f);
// Different borders indicate receptivity to drops
static Border normalBorder = new LineBorder(Color.black, 3);
static Border canDropBorder = new BevelBorder(BevelBorder.LOWERED);
// The constructor method
public TransferableScribblePane() {
setPreferredSize(new Dimension(450,200)); // We need a default size
setBorder(normalBorder); // and a border.
lines = new ArrayList(); // Start with an empty list of lines
// Register interest in mouse button and mouse motion events.
enableEvents(AWTEvent.MOUSE_EVENT_MASK |
AWTEvent.MOUSE_MOTION_EVENT_MASK);
// Enable drag-and-drop by specifying a listener that will be
// notified when a drag begins. dragGestureListener is defined later.
DragSource dragSource = DragSource.getDefaultDragSource();
dragSource.createDefaultDragGestureRecognizer(this,
DnDConstants.ACTION_COPY_OR_MOVE,
dragGestureListener);
// Enable drops on this component by registering a listener to
// be notified when something is dragged or dropped over us.
this.setDropTarget(new DropTarget(this, dropTargetListener));
// Check whether the system allows us to drag an image of the line
canDragImage = dragSource.isDragImageSupported();
}
/** We override this method to draw ourselves. */
public void paintComponent(Graphics g) {
// Let the superclass do its painting first
super.paintComponent(g);
// Make a copy of the Graphics context so we can modify it
Graphics2D g2 = (Graphics2D) (g.create());
// Our superclass doesn't paint the background, so do this ourselves.
g2.setColor(getBackground());
g2.fillRect(0, 0, getWidth(), getHeight());
// Set the line width and color to use for the foreground
g2.setStroke(stroke);
g2.setColor(this.getForeground());
// Now loop through the PolyLine shapes and draw them all
int numlines = lines.size();
for(int i = 0; i < numlines; i++) {
PolyLine line = (PolyLine)lines.get(i);
if (line == selectedLine) { // If it is the selected line
g2.setStroke(selectedStroke); // Set dash pattern
g2.draw(line); // Draw the line
g2.setStroke(stroke); // Revert to solid lines
}
else g2.draw(line); // Otherwise just draw the line
}
}
/**
* This method is called on mouse button events. It begins a new line
* or tries to select an existing line.
*/
public void processMouseEvent(MouseEvent e) {
if (e.getButton() == MouseEvent.BUTTON1) { // Left mouse button
if (e.getID() == MouseEvent.MOUSE_PRESSED) { // Pressed down
if (e.isShiftDown()) { // with Shift key
// If the shift key is down, try to select a line
int x = e.getX();
int y = e.getY();
// Loop through the lines checking to see if we hit one
PolyLine selection = null;
int numlines = lines.size();
for(int i = 0; i < numlines; i++) {
PolyLine line = (PolyLine)lines.get(i);
if (line.intersects(x-2, y-2, 4, 4)) {
selection = line;
e.consume();
break;
}
}
// If we found an intersecting line, save it and repaint
if (selection != selectedLine) { // If selection changed
selectedLine = selection; // remember which is selected
repaint(); // will make selection dashed
}
}
else if (!e.isControlDown()) { // no shift key or ctrl key
// Start a new line on mouse down without shift or ctrl
currentLine = new PolyLine(e.getX(), e.getY());
lines.add(currentLine);
e.consume();
}
}
else if (e.getID() == MouseEvent.MOUSE_RELEASED) {// Left Button Up
// End the line on mouse up
if (currentLine != null) {
currentLine = null;
e.consume();
}
}
}
// The superclass method dispatches to registered event listeners
super.processMouseEvent(e);
}
/**
* This method is called for mouse motion events.
* We don't have to detect gestures that initiate a drag in this method.
* That is the job of the DragGestureRecognizer we created in the
* constructor: it will notify the DragGestureListener defined below.
*/
public void processMouseMotionEvent(MouseEvent e) {
if (e.getID() == MouseEvent.MOUSE_DRAGGED && // If we're dragging
currentLine != null) { // and a line exists
currentLine.addSegment(e.getX(), e.getY()); // Add a line segment
e.consume(); // Eat the event
repaint(); // Redisplay all lines
}
super.processMouseMotionEvent(e); // Invoke any listeners
}
/** Copy the selected line to the clipboard, then delete it */
public void cut() {
if (selectedLine == null) return; // Only works if a line is selected
copy(); // Do a Copy operation...
lines.remove(selectedLine); // and then erase the selected line
selectedLine = null;
repaint(); // Repaint because a line was removed
}
/** Copy the selected line to the clipboard */
public void copy() {
if (selectedLine == null) return; // Only works if a line is selected
// Get the system Clipboard object.
Clipboard c = this.getToolkit().getSystemClipboard();
// Wrap the selected line in a TransferablePolyLine object
// and pass it to the clipboard, with an object to receive notification
// when some other application takes ownership of the clipboard
c.setContents(new TransferablePolyLine((PolyLine)selectedLine.clone()),
new ClipboardOwner() {
public void lostOwnership(Clipboard c,Transferable t){
// This method is called when something else
// is copied to the clipboard. We could use it
// to deselect the selected line, if we wanted.
}
});
}
/** Get a PolyLine from the clipboard, if one exists, and display it */
public void paste() {
// Get the system Clipboard and ask for its Transferable contents
Clipboard c = this.getToolkit().getSystemClipboard();
Transferable t = c.getContents(this);
// See if we can extract a PolyLine from the Transferable object
PolyLine line;
try {
line = (PolyLine)t.getTransferData(TransferablePolyLine.FLAVOR);
}
catch(Exception e) { // UnsupportedFlavorException or IOException
// If we get here, the clipboard doesn't hold a PolyLine we can use
getToolkit().beep(); // So beep to indicate the error
return;
}
lines.add(line); // We got a line from the clipboard, so add it to list
repaint(); // And repaint to make the line appear
}
/** Erase all lines and repaint. */
public void clear() {
lines.clear();
repaint();
}
/**
* This DragGestureListener is notified when the user initiates a drag.
* We passed it to the DragGestureRecognizer we created in the constructor.
*/
public DragGestureListener dragGestureListener = new DragGestureListener(){
public void dragGestureRecognized(DragGestureEvent e) {
// Don't start a drag if there isn't a selected line
if (selectedLine == null) return;
// Find out where the drag began
MouseEvent trigger = (MouseEvent)e.getTriggerEvent();
int x = trigger.getX();
int y = trigger.getY();
// Don't do anything if the drag was not near the selected line
if (!selectedLine.intersects(x-4, y-4, 8, 8)) return;
// Make a copy of the selected line, adjust the copy so that
// the point under the mouse is (0,0), and wrap the copy in a
// Tranferable wrapper.
PolyLine copy = (PolyLine)selectedLine.clone();
copy.translate(-x, -y);
Transferable t = new TransferablePolyLine(copy);
// If the system allows custom images to be dragged, make
// an image of the line on a transparent background
Image dragImage = null;
Point hotspot = null;
if (canDragImage) {
Rectangle box = copy.getBounds();
dragImage = createImage(box.width, box.height);
Graphics2D g = (Graphics2D)dragImage.getGraphics();
g.setColor(new Color(0,0,0,0)); // transparent bg
g.fillRect(0, 0, box.width, box.height);
g.setColor(getForeground());
g.setStroke(selectedStroke);
g.translate(-box.x, -box.y);
g.draw(copy);
hotspot = new Point(-box.x, -box.y);
}
// Now begin dragging the line, specifying the listener
// object to receive notifications about the progress of
// the operation. Note: the startDrag() method is defined by
// the event object, which is unusual.
e.startDrag(null, // Use default drag-and-drop cursors
dragImage, // Use the image, if supported
hotspot, // Ditto for the image hotspot
t, // Drag this object
dragSourceListener); // Send notifications here
}
};
/**
* If this component is the source of a drag, then this DragSourceListener
* will receive notifications about the progress of the drag. The only
* one we use here is dragDropEnd() which is called after a drop occurs.
* We could use the other methods to change cursors or perform other
* "drag over effects"
*/
public DragSourceListener dragSourceListener = new DragSourceListener() {
// Invoked when dragging stops
public void dragDropEnd(DragSourceDropEvent e) {
if (!e.getDropSuccess()) return; // Ignore failed drops
// If the drop was a move, then delete the selected line
if (e.getDropAction() == DnDConstants.ACTION_MOVE) {
lines.remove(selectedLine);
selectedLine = null;
repaint();
}
}
// The following methods are unused here. We could implement them
// to change custom cursors or perform other "drag over effects".
public void dragEnter(DragSourceDragEvent e) {}
public void dragExit(DragSourceEvent e) {}
public void dragOver(DragSourceDragEvent e) {}
public void dropActionChanged(DragSourceDragEvent e) {}
};
/**
* This DropTargetListener is notified when something is dragged over
* this component.
*/
public DropTargetListener dropTargetListener = new DropTargetListener() {
// This method is called when something is dragged over us.
// If we understand what is being dragged, then tell the system
// we can accept it, and change our border to provide extra
// "drag under" visual feedback to the user to indicate our
// receptivity to a drop.
public void dragEnter(DropTargetDragEvent e) {
if (e.isDataFlavorSupported(TransferablePolyLine.FLAVOR)) {
e.acceptDrag(e.getDropAction());
setBorder(canDropBorder);
}
}
// Revert to our normal border if the drag moves off us.
public void dragExit(DropTargetEvent e) { setBorder(normalBorder); }
// This method is called when something is dropped on us.
public void drop(DropTargetDropEvent e) {
// If a PolyLine is dropped, accept either a COPY or a MOVE
if (e.isDataFlavorSupported(TransferablePolyLine.FLAVOR))
e.acceptDrop(e.getDropAction());
else { // Otherwise, reject the drop and return
e.rejectDrop();
return;
}
// Get the dropped object and extract a PolyLine from it
Transferable t = e.getTransferable();
PolyLine line;
try {
line =
(PolyLine)t.getTransferData(TransferablePolyLine.FLAVOR);
}
catch(Exception ex) { // UnsupportedFlavor or IOException
getToolkit().beep(); // Something went wrong, so beep
e.dropComplete(false); // Tell the system we failed
return;
}
// Figure out where the drop occurred, and translate so the
// point that was formerly (0,0) is now at that point.
Point p = e.getLocation();
line.translate((float)p.getX(), (float)p.getY());
// Add the line to our list, and repaint
lines.add(line);
repaint();
// Tell the system that we successfully completed the transfer.
// This means it is safe for the initiating component to delete
// its copy of the line
e.dropComplete(true);
}
// We could provide additional drag under effects with this method.
public void dragOver(DropTargetDragEvent e) {}
// If we used custom cursors, we would update them here.
public void dropActionChanged(DropTargetDragEvent e) {}
};
}
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