import java.applet.Applet; import java.awt.*; import java.awt.event.*; public class ClickMeErase extends Applet implements MouseListener { private Spot spot = new Spot(RADIUS); private Spot previousSpot = new Spot(RADIUS); private static final int RADIUS = 7; public void init() { addMouseListener(this); } public void update(Graphics g) { // erase the old spot g.setColor(Color.white); if (previousSpot.x != -1 && previousSpot.y != -1) { g.fillOval(previousSpot.x - RADIUS, previousSpot.y - RADIUS, RADIUS * 2, RADIUS * 2); } // draw the spot g.setColor(Color.red); if (spot.x != -1 && spot.y != -1) { g.fillOval(spot.x - RADIUS, spot.y - RADIUS, RADIUS * 2, RADIUS * 2); } } public void paint(Graphics g) { // draw a black border and a white background g.setColor(Color.white); g.fillRect(0, 0, getSize().width - 1, getSize().height - 1); g.setColor(Color.black); g.drawRect(0, 0, getSize().width - 1, getSize().height - 1); update(g); } public void mousePressed(MouseEvent event) { previousSpot.x = spot.x; previousSpot.y = spot.y; spot.x = event.getX(); spot.y = event.getY(); repaint(); } public void mouseClicked(MouseEvent event) {} public void mouseReleased(MouseEvent event) {} public void mouseEntered(MouseEvent event) {} public void mouseExited(MouseEvent event) {} }