Constant Mouse

Question

Hello. My name is Chris. I took a basic java introduction class during the summer. My teacher created a graph program/sprite/turtle(logo)/keyboard/applet program. I know how to get all of that working. All I need to know is hoe I can have a constant mouse catcher. Here is my code (without all of the other stuff):
while(true) {
//loop forever
mx=g.getMouseX();
//mx is a double
//g.getMouseX(); saves last mouse click x in mx
my=g.getMouseY();
//same as above, only for Y variable (of mouse)
Tim.setPosition(mx,my);
//Send invisible Tim, the Turtle to the place where the mouse was clicked
Tim.forward(.01);
//Tim makes a mark there.
Now what I want is something that will allow me to make lines instead of just dots. So it will pick up when I have the mouse held down. How can I do this?
Thanks,
Chris

Answer 1

Here is my PaintArea class. This should give you some idea about how mouse listeners work, and may be along the lines of what you're looking for.
You are free to use and modify the code, but please do not change the package or take credit for it as your own.
BTW, if you're trying to do this as a challenge, this may be kind of a spoiler, so if you want the thrill of figuring it all out, stop here.
PaintArea.java
===========
* Created on Jun 15, 2005 by @author Tom Jacobs
package tjacobs.ui;
import java.awt.image.BufferedImage;
import java.awt.*;
import java.awt.event.*;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.ImageIcon;
import javax.swing.JComboBox;
import javax.swing.JComponent;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JToolBar;
import javax.swing.SwingUtilities;
import tjacobs.MathUtils;
public class PaintArea extends JComponent {
     BufferedImage mImg; //= new BufferedImage();
     int mBrushSize = 1;
     private boolean mSizeChanged = false;
     private Color mColor1, mColor2;
     static class PaintIcon extends ImageIcon {
          int mSize;
          public PaintIcon(Image im, int size) {
               super(im);
               mSize = size;
     public PaintArea() {
          super();
          setCursor(Cursor.getPredefinedCursor(Cursor.CROSSHAIR_CURSOR));
          addComponentListener(new CListener());
          MListener ml = new MListener();
          addMouseListener(ml);
          addMouseMotionListener(ml);
          setBackground(Color.WHITE);
          setForeground(Color.BLACK);
     public void paintComponent(Graphics g) {
          if (mSizeChanged) {
               handleResize();
          //g.drawImage(mImg, mImg.getWidth(), mImg.getHeight(), null);
          g.drawImage(mImg, 0, 0, null);
          //super.paintComponent(g);
          //System.out.println("Image = " + mImg);
          //System.out.println("Size: " + mImg.getWidth() + "," + mImg.getHeight());
     public void setBackground(Color c) {
          super.setBackground(c);
          if (mImg != null) {
               Graphics g = mImg.getGraphics();
               g.setColor(c);
               g.fillRect(0, 0, mImg.getWidth(), mImg.getHeight());
               g.dispose();
     public void setColor1(Color c) {
          mColor1 = c;
     public void setColor2(Color c) {
          mColor2 = c;
     public Color getColor1() {
          return mColor1;
     public Color getColor2() {
          return mColor2;
     class ToolBar extends JToolBar {
          ToolBar() {
               final ColorButton fore = new ColorButton();
               fore.setToolTipText("Foreground Color");
               final ColorButton back = new ColorButton();
               back.setToolTipText("Background Color");
               JComboBox brushSize = new JComboBox();
               //super.createImage(1, 1).;
               FontMetrics fm = new FontMetrics(getFont()) {};
               int ht = fm.getHeight();
               int useheight = fm.getHeight() % 2 == 0 ? fm.getHeight() + 1 : fm.getHeight();
               final BufferedImage im1 = new BufferedImage(useheight, useheight, BufferedImage.TYPE_INT_RGB);
               Graphics g = im1.getGraphics();
               g.setColor(Color.WHITE);
               g.fillRect(0, 0, useheight, useheight);
               g.setColor(Color.BLACK);
               g.fillOval(useheight / 2, useheight / 2, 1, 1);
               g.dispose();
               //im1.setRGB(useheight / 2 + 1, useheight / 2 + 1, 0xFFFFFF);
               final BufferedImage im2 = new BufferedImage(useheight, useheight, BufferedImage.TYPE_INT_RGB);
               g = im2.getGraphics();
               g.setColor(Color.WHITE);
               g.fillRect(0, 0, useheight, useheight);
               g.setColor(Color.BLACK);
               g.fillOval(useheight / 2 - 1, useheight / 2 - 1, 3, 3);
               g.dispose();
//               im2.setRGB(useheight / 2 - 1, useheight / 2 - 1, 3, 3, new int[] {     0, 0xFFFFFF, 0,
//                                                            0xFFFFFF, 0xFFFFFFF, 0xFFFFFF,
//                                                            0, 0xFFFFFF, 0}, 0, 1);
               final BufferedImage im3 = new BufferedImage(useheight, useheight, BufferedImage.TYPE_INT_RGB);
               g = im3.getGraphics();
               g.setColor(Color.WHITE);
               g.fillRect(0, 0, useheight, useheight);
               g.setColor(Color.BLACK);
               g.fillOval(useheight / 2 - 2, useheight / 2 - 2, 5, 5);
               g.dispose();
//               im3.setRGB(useheight / 2 - 2, useheight / 2 - 2, 5, 5, new int[] {     0, 0, 0xFFFFFF, 0, 0, 
//                                                            0, 0xFFFFFF, 0xFFFFFFF, 0xFFFFFF, 0,
//                                                            0xFFFFFF, 0xFFFFFF, 0xFFFFFF, 0xFFFFFF, 0xFFFFFF,
//                                                            0, 0xFFFFFF, 0xFFFFFFF, 0xFFFFFF, 0,
//                                                            0, 0, 0xFFFFFF, 0, 0}, 0, 1);
               //JLabel l1 = new JLabel("1 pt", new ImageIcon(im1), JLabel.LEFT);
               //JLabel l2 = new JLabel("3 pt", new ImageIcon(im2), JLabel.LEFT);
               //JLabel l3 = new JLabel("5 pt", new ImageIcon(im3), JLabel.LEFT);
               brushSize.addItem(new PaintIcon(im1, 1));
               brushSize.addItem(new PaintIcon(im2, 3));
               brushSize.addItem(new PaintIcon(im3, 5));
               //brushSize.addItem("Other");
               add(fore);
               add(back);
               add(brushSize);
               PropertyChangeListener pl = new PropertyChangeListener() {
                    public void propertyChange(PropertyChangeEvent ev) {
                         Object src = ev.getSource();
                         if (src != fore && src != back) {
                              return;
                         Color c = (Color) ev.getNewValue();
                         if (ev.getSource() == fore) {
                              mColor1 = c;
                         else {
                              mColor2 = c;
               fore.addPropertyChangeListener("Color", pl);
               back.addPropertyChangeListener("Color", pl);
               fore.changeColor(Color.BLACK);
               back.changeColor(Color.WHITE);
               brushSize.addItemListener(new ItemListener() {
                    public void itemStateChanged(ItemEvent ev) {
                         System.out.println("ItemEvent");
                         if (ev.getID() == ItemEvent.DESELECTED) {
                              return;
                         System.out.println("Selected");
                         Object o = ev.getItem();
                         mBrushSize = ((PaintIcon) o).mSize;
               //Graphics g = im1.getGraphics();
               //g.fillOval(0, 0, 1, 1);
               //BufferedImage im1 = new BufferedImage();
               //BufferedImage im1 = new BufferedImage();
     protected class MListener extends MouseAdapter implements MouseMotionListener {
          Point mLastPoint;
          public void mouseDragged(MouseEvent me) {
               Graphics g = mImg.getGraphics();
               if ((me.getModifiers() & InputEvent.BUTTON1_MASK) != 0) {
                    g.setColor(mColor1);
               } else {
                    g.setColor(mColor2);
               Point p = me.getPoint();
               if (mLastPoint == null) {
                    g.fillOval(p.x - mBrushSize / 2, p.y - mBrushSize / 2, mBrushSize, mBrushSize);
                    //g.drawLine(p.x, p.y, p.x, p.y);
               else {
                    g.drawLine(mLastPoint.x, mLastPoint.y, p.x, p.y);
                    //g.fillOval(p.x - mBrushSize / 2, p.y - mBrushSize / 2, mBrushSize, mBrushSize);
                    double angle = MathUtils.angle(mLastPoint, p);
                    if (angle < 0) {
                         angle += 2 * Math.PI;
                    double distance = MathUtils.distance(mLastPoint, p) * 1.5;
                    if (angle < Math.PI / 4 || angle > 7 * Math.PI / 4 || Math.abs(Math.PI - angle) < Math.PI / 4) {
                         for (int i = 0; i < mBrushSize / 2; i ++) {
                              g.drawLine(mLastPoint.x, mLastPoint.y + i, p.x, p.y + i);
                              g.drawLine(mLastPoint.x, mLastPoint.y - i, p.x, p.y - i);
//                              System.out.println("y");
//                              System.out.println("angle = " + angle / Math.PI * 180);
                    else {
                         for (int i = 0; i < mBrushSize / 2; i ++) {
                              g.drawLine(mLastPoint.x + i, mLastPoint.y, p.x + i, p.y);
                              g.drawLine(mLastPoint.x  - i, mLastPoint.y, p.x - i, p.y);
//                              System.out.println("x");
//                    System.out.println("new = " + PaintUtils.printPoint(p));
//                    System.out.println("last = " + PaintUtils.printPoint(mLastPoint));
                    //System.out.println("distance = " + distance);
                    //Graphics2D g2 = (Graphics2D) g;
                    //g2.translate(mLastPoint.x + mBrushSize / 2, mLastPoint.y);
                    //g2.rotate(angle);
                    //g2.fillRect(0, 0, (int) Math.ceil(distance), mBrushSize);
                    //g2.rotate(-angle);
                    //g2.translate(-mLastPoint.x + mBrushSize / 2, -mLastPoint.y);
//                    g.setColor(Color.RED);
//                    g.drawRect(p.x, p.y, 1, 1);
               mLastPoint = p;
               g.dispose();
               repaint();
          public void mouseMoved(MouseEvent me) {}
          public void mouseReleased(MouseEvent me) {
               mLastPoint = null;
     private void handleResize() {
          Dimension size = getSize();
          mSizeChanged = false;
          if (mImg == null) {
               mImg = new BufferedImage(size.width, size.height, BufferedImage.TYPE_INT_RGB);
               Graphics g = mImg.getGraphics();
               g.setColor(getBackground());
               g.fillRect(0, 0, mImg.getWidth(), mImg.getHeight());
               g.dispose();
          else {
               int newWidth = Math.max(mImg.getWidth(),getWidth());
               int newHeight = Math.max(mImg.getHeight(),getHeight());
               if (newHeight == mImg.getHeight() && newWidth == mImg.getWidth()) {
                    return;
               BufferedImage bi2 = new BufferedImage(newWidth, newHeight, BufferedImage.TYPE_INT_RGB);
               Graphics g = bi2.getGraphics();
               g.setColor(getBackground());
               g.fillRect(0, 0, bi2.getWidth(), bi2.getHeight());
               g.drawImage(mImg, mImg.getWidth(), mImg.getHeight(), null);
               g.dispose();
               mImg = bi2;
     public JToolBar getToolBar() {
          if (mToolBar == null) {
               mToolBar = new ToolBar();
          return mToolBar;
     private ToolBar mToolBar;
     public static void main (String args[]) {
          PaintArea pa = new PaintArea();
          JPanel parent = new JPanel();
          parent.setLayout(new BorderLayout());
          parent.add(pa, BorderLayout.CENTER);
          pa.setPreferredSize(new Dimension(150, 150));
          parent.add(pa.getToolBar(), BorderLayout.NORTH);
          WindowUtilities.visualize(parent);
     protected class CListener extends ComponentAdapter {
          public void componentResized(ComponentEvent ce) {
               mSizeChanged = true;
}