Displaying a Shape?

Question

I am creating an application that does screen capture of the desktop. I have it working for the most part. I am using the Robot class to capture a 640x480 Rectangle on the screen that is centered using the current position of the mouse.
So that the user can see the area that is being captured I would like to add a visual Rectangle to the screen that just has the stroke outlined? I am at a loss for where or how to do this. It seams like all the examples I see for drawing shapes has you draw them to a JFrame or some other component. Could you guys suggest to me how I may just add a Raw Outlined Rectangle to the screen? Once I know how to do that I am pretty sure I can get it to follow the Mouse.
-Matthew

Answer 1

You can't really paint over the screen in general (I mean you can, but you've got to create a (J)Window and fill it with a screen-captured Image first) but if you're talking about screen capture over a java app, check out this class
package tjacobs.ui.drag;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Component;
import java.awt.Container;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Stroke;
import java.awt.event.*;
import java.util.ArrayList;
import java.util.Iterator;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import tjacobs.ui.util.WindowClosingActions;
* See the public static method addAMouseDragOutliner
public class MouseDragOutliner extends MouseAdapter implements MouseMotionListener {
     public static final BasicStroke DASH_STROKE = new BasicStroke(1.0f, BasicStroke.CAP_SQUARE, BasicStroke.JOIN_BEVEL, 10.0f, new float[] {8, 8}, 0);
     public static final boolean RECTANGLE = true;
     public static final boolean OVAL = false;
     private boolean mUseMove = false;
     private Point mStart;
     private Point mEnd;
     private boolean mShape = RECTANGLE;
     private Component mComponent;
     private MyRunnable mRunner= new MyRunnable();
     private ArrayList mListeners = new ArrayList(1);
     public MouseDragOutliner() {
          super();
     public MouseDragOutliner(boolean useMove) {
          this();
          mUseMove = useMove;
     public void setShape(boolean b) {
          mShape = b;
     public void mouseDragged(MouseEvent me) {
          doMouseDragged(me);
     public void mousePressed(MouseEvent me) {
          mStart = me.getPoint();
     public void mouseEntered(MouseEvent me) {
          mStart = me.getPoint();
     public void mouseReleased(MouseEvent me) {
          Iterator i = mListeners.iterator();
          Point end = me.getPoint();
          while (i.hasNext()) {
               ((OutlineListener)i.next()).mouseDragEnded(mStart, end);
          //mStart = null;
     public void mouseMoved(MouseEvent me) {
          if (mUseMove) {
               doMouseDragged(me);
     public     void addOutlineListener(OutlineListener ol) {
          mListeners.add(ol);
     public void removeOutlineListener(OutlineListener ol) {
          mListeners.remove(ol);
     private class MyRunnable implements Runnable {
          public void run() {
               Graphics g = mComponent.getGraphics();
               if (g == null) {
                    return;
               Graphics2D g2 = (Graphics2D) g;
               Stroke s = g2.getStroke();
               g2.setStroke(DASH_STROKE);
               int x = Math.min(mStart.x, mEnd.x);
               int y = Math.min(mStart.y, mEnd.y);
               int w = Math.abs(mEnd.x - mStart.x);
               int h = Math.abs(mEnd.y - mStart.y);
               g2.setXORMode(Color.WHITE);
               if (mShape == RECTANGLE) g2.drawRect(x, y, w, h);
               else g2.drawOval(x, y, w, h);
               g2.setStroke(s);
     public void doMouseDragged(MouseEvent me) {
          mEnd = me.getPoint();
          if (mStart != null) {
               mComponent = me.getComponent();
               mComponent.repaint();
               SwingUtilities.invokeLater(mRunner);
     public static MouseDragOutliner addAMouseDragOutliner(Component c) {
          MouseDragOutliner mdo = new MouseDragOutliner();
          c.addMouseListener(mdo);
          c.addMouseMotionListener(mdo);
          return mdo;
     public static interface OutlineListener {
          public void mouseDragEnded(Point start, Point finish);
     public static void main(String[] args) {
          JFrame f = new JFrame("MouseDragOutliner Test");
          Container c = f.getContentPane();
          JPanel p = new JPanel();
          //p.setBackground(Color.BLACK);
          c.add(p);
          MouseDragOutliner outliner = addAMouseDragOutliner(p);
          outliner.setShape(OVAL);
          f.setBounds(200, 200, 400, 400);
          f.addWindowListener(new WindowClosingActions.Exit());
          f.setVisible(true);
}