methods in interfaces

[kanna chakravarthi]

Dear sir/Madam,

Refer attached document
please tell me how the following methods are being invoked
"public void mouseClicked(MouseEvent me)"
"public void mouseEntered(MouseEvent me)".... etc
when i am clicking the mouse button, how the "public void mouseClicked(MouseEvent me)" is being called

whats the connection between my mouse button and that method.
as interfaces only define the methods and we have to implement and add the logic inside that method,then how this method is being invoked when my mouse is clicked, i didnot write any code to let the jvm invoke this particular method when i press the button
as in applets there are no instances created JVM will invoke the methods but how does JVM knows to invoke that particular method when i clicked the mouse button.

waiting for reply and thank you very much in advance

Rgds

[Michael Dunn]

Refer attached document

http://docs.oracle.com/javase/tutorial/uiswing/events/intro.html

[Campbell Ritchie]

And welcome to the Ranch

[kanna chakravarthi]

Michael Dunn wrote:Refer attached document

http://docs.oracle.com/javase/tutorial/uiswing/events/intro.html

sir i came to know how to handle events but coudnt understand whats actually happening inside when i am clicking a mouse button
mouseListener interface is having 5 methods but when i click the mouse button the mouseClicked method is being invoked
why not another method such as mouseEntered is not being invoked.how this exact mapping of my mouse and these methods are
done.how this is being done

[kanna chakravarthi]

thank you sir very glad to hear from you

[kanna chakravarthi]

Campbell Ritchie wrote:And welcome to the Ranch

thank you sir

[Michael Dunn]

> why not another method such as mouseEntered is not being invoked

how do you know that to be true?

post some code showing that mouseEntered does not fire

[kanna chakravarthi]

Michael Dunn wrote:> why not another method such as mouseEntered is not being invoked

how do you know that to be true?

post some code showing that mouseEntered does not fire

please find the attached filw sir

[kanna chakravarthi]

import java.awt.*;
import java.awt.event.*;
import java.applet.*;
/*
<applet code="mouseevents" width=300 height=300>
</applet>
*/

public class mouseevents extends Applet implements MouseListener,MouseMotionListener
{
String msg="";
int mouseX=0,mouseY=0;

public void init()
{
addMouseListener(this);
addMouseMotionListener(this);
}
public void mouseClicked(MouseEvent me)
{
mouseX=0;
mouseY=10;
msg="mouseclicked";
repaint();
}

public void mouseEntered(MouseEvent me)
{
mouseX=0;
mouseY=10;
msg="mouseentered";
repaint();
}

public void mouseExited(MouseEvent me)
{
mouseX=0;
mouseY=10;
msg="mouseExited";
repaint();
}

public void mousePressed(MouseEvent me)
{
mouseX=me.getX();
mouseY=me.getY();
msg="down";
repaint();
}

public void mouseReleased(MouseEvent me)
{
mouseX=me.getX();
mouseY=me.getY();
msg="up";
repaint();
}

public void mouseDragged(MouseEvent me)
{
mouseX=me.getX();
mouseY=me.getY();
msg="*";
showStatus("dragging mouse at"+mouseX+","+mouseY);
repaint();
}

public void mouseMoved(MouseEvent me)
{
showStatus("mouse moving at"+me.getX()+","+me.getY());
}

public void paint(Graphics g)
{
g.drawString(msg,mouseX,mouseY);
}
}

[Michael Dunn]

the posted code proves all methods fire, so what's the problem?

[kanna chakravarthi]

sir yes all methods are firing when i do the appropriate operation on the output screen.
my question is how the mouseClicked method is being fired when i click the mouse button.How this invocation is being done.
actually we should call a method without any call how this method is being invoked.will jvm observe the mouse operations and invoke ?
if so when i click my mouse button how does jvm know to invoke mouseClicked method particularly.

[Michael Dunn]

Swing is 'event' driven - all events are fired.

your program registers listeners for specific events it wants to be notified when happened (mouse/key/action/whatever).

here's a simple program to play around with.
click anywhere on the panel (there's no mouseListener 'added' to the panel).

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class Testing
{
  Point pt = new Point(0,0);
  public void buildGUI()
  {
    final JPanel p = new JPanel(){
      public void paintComponent(Graphics g){
        super.paintComponent(g);
        g.drawString("Clicked here.",pt.x-8,pt.y-25);
      }
    };
    JFrame f = new JFrame();
    f.add(p);
    f.setSize(800,600);
    f.setLocationRelativeTo(null);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setVisible(true);
    Toolkit.getDefaultToolkit().addAWTEventListener( new AWTEventListener()
    {
      public void eventDispatched(AWTEvent e)
      {
        if(e.getID() == MouseEvent.MOUSE_PRESSED)
        {
          pt = ((MouseEvent)e).getPoint();
          p.repaint();
        }
      }
    },AWTEvent.MOUSE_EVENT_MASK);
  }
  public static void main(String[] args)
  {
    SwingUtilities.invokeLater(new Runnable(){
      public void run(){
        new Testing().buildGUI();
      }
    });
  }
}