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Asked: 2026-05-10T13:38:09+00:00

So I’ve got a JPanel implementing MouseListener and MouseMotionListener : import javax.swing.*; import java.awt.*;

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So I’ve got a JPanel implementing MouseListener and MouseMotionListener:

import javax.swing.*; import java.awt.*; import java.awt.event.*;  public class DisplayArea extends JPanel implements MouseListener, MouseMotionListener  {     public DisplayArea(Rectangle bounds, Display display) {         setLayout(null);         setBounds(bounds);         setOpaque(false);         setPreferredSize(new Dimension(bounds.width, bounds.height));          this.display = display;     }      public void paintComponent(Graphics g) {          Graphics2D g2 = (Graphics2D)g;          if (display.getControlPanel().Antialiasing()) {              g2.addRenderingHints(new RenderingHints(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON));          }          g2.setColor(Color.white);          g2.fillRect(0, 0, getWidth(), getHeight());     }      public void mousePressed(MouseEvent event) {         System.out.println('mousePressed()');         mx1 = event.getX();         my1 = event.getY();     }      public void mouseReleased(MouseEvent event) {         System.out.println('mouseReleased()');         mx2 = event.getX();         my2 = event.getY();          int mode = display.getControlPanel().Mode();         switch (mode) {         case ControlPanel.LINE:              System.out.println('Line from ' + mx1 + ', ' + my1 + ' to ' + mx2 + ', ' + my2 + '.');         }     }      public void mouseEntered(MouseEvent event) {         System.out.println('mouseEntered()');     }      public void mouseExited(MouseEvent event) {         System.out.println('mouseExited()');     }      public void mouseClicked(MouseEvent event) {         System.out.println('mouseClicked()');     }      public void mouseMoved(MouseEvent event) {         System.out.println('mouseMoved()');     }      public void mouseDragged(MouseEvent event) {          System.out.println('mouseDragged()');     }      private Display display = null;      private int mx1 = -1;     private int my1 = -1;     private int mx2 = -1;     private int my2 = -1; }

The trouble is, none of these mouse functions are ever called. DisplayArea is created like this:

da = new DisplayArea(new Rectangle(CONTROL_WIDTH, 0, DISPLAY_WIDTH, DISPLAY_HEIGHT), this);

I am not really a Java programmer (this is part of an assignment), but I can’t see anything glaringly obvious. Can someone smarter than I see anything?

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1 Answer

  1. The implements mouselistener, mousemotionlistener just allows the displayArea class to listen to some, to be defined, Swing component’s mouse events. You have to explicitly define what it should be listening at. So I suppose you could add something like this to the constructor:

    this.addMouseListener(this); this.addMouseMotionListener(this);
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