Draw a line using mouse

Question

Hello there:
I'm trying to draw a line using mouse pointer: My code is:
public class DrawLine extends JFrame implements MouseListener, MouseMotionListener
    int x0, y0, x1, y1;  
    public DrawLine()
         addMouseListener(this);
         addMouseMotionListener(this);
    public void mouseDragged(MouseEvent e)
         x1 = e.getX();
         y1 = e.getY();
         repaint();
    public void mouseMoved(MouseEvent e) { }
    public void mouseClicked(MouseEvent e){ }
    public void mouseEntered(MouseEvent e) { }
    public void mouseExited (MouseEvent e) { }
    public void mousePressed(MouseEvent e)
          x0 = e.getX();
          y0 = e.getY();           
    public void mouseReleased(MouseEvent e)
          x1 = e.getX();
          y1 = e.getY();
   public void paint(Graphics g)
             g.setColor(Color.BLACK);
          g.drawLine(x0, y0, x1, y1);
    public static void main(String[] argv)
         DrawLine dr=new DrawLine("Test");
         dr.setVisible(true);
         dr.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}when mouse is dragged, multiple lines are being drawn....
could you else please tell me what should I've to do???
thanks n regards...
Dev

Answer 1

You can implement the listeners on any class, even one that (implicitly) extends Object. What matters is that the listener is added to the component that needs to use it.
That said, why do you want to extend JFrame? Are you adding functionality to the JFrame to justify extending the JFC class? Note that extending JFrame allows the users of your class to access the functionality of a JFrame, is that really indicated here?
one class that extends JFrame, and one can draw a line on JLabel, embedded within JFrame!So you still have to override paintComponent of the JLabel, which implies using an anonymous inner class.
Starting with the example already posted, that would be:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;
public class DrawLineTest
    implements MouseListener, MouseMotionListener {
  JLabel label;
  int x0, y0, x1, y1;
  private void makeUI() {
    JFrame frame = new JFrame("DrawLineTest");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    label = new JLabel("FFFF") {
      public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.setColor(Color.BLACK);
        g.drawLine(x0, y0, x1, y1);
    label.setPreferredSize(new Dimension(500, 500));
    label.addMouseListener(this);
    label.addMouseMotionListener(this);
    frame.add(label);
    frame.pack();
    frame.setVisible(true);
  public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
      public void run() {
        new DrawLineTest().makeUI();
  public void mousePressed(MouseEvent e) {
    x0 = e.getX();
    y0 = e.getY();      
  public void mouseReleased(MouseEvent e) {
    x1 = e.getX();
    y1 = e.getY();
  public void mouseDragged(MouseEvent e) {
    x1 = e.getX();
    y1 = e.getY();
    label.repaint();
  public void mouseMoved(MouseEvent e) { }
  public void mouseClicked(MouseEvent e){ }
  public void mouseEntered(MouseEvent e) { }
  public void mouseExited (MouseEvent e) { }
}Better spend more time with the tutorials, there's a separate section on writing event listeners.
db