where to define eventhandler

[shree vijay]

Hi,
I have a class called POFrame which has instance variables:
1. Panel1
2.Panel2
3.Panel3
4.Panel4
5.Panel5.
Panel3 encloses Panel1 and Panel2.
In Panel1 there is a Choice object where i have
1. Option1
2. Option2.
There is a List Object in Panel2. When i create it , i populate it with 3 items corresponding to the Option1 in Panel1.
Now, here is my problem:
If after the frame is displayed, the user selects Option2 (an ItemEvent), then i should change the 3 items in the list in Panel2 corresponding to the new Option. How do i go about it?
I tried to remove the List from the Panel2 and repopulate it and then add it.
Also, where should i write the eventhandler? I wrote it in a separate class, but when i compile it gives me the error that it is not able to find Panel1,Panel2,and so on, though Panel1...Panel5 are all default instance variables of the POFrame class.
Rgds,
Shree
p.s. If i have not made a good job of explaining the problem, i
will post the program... I guessed people wouldn't prefer going through a lot of lines of code...

[shree vijay]

Hi,
Shown below is the whole program:
If i remove the comments , the program doesn't compile. I tried quite a bit to solve this on my own, but couldn't. Also, am i doing it right when i am defining the event handler as i have done here? All the code gets packed into the constructor and this class itself, i sense something awkward about it.
/* Creating a purchase order screen */
import java.awt.*;
import javax.swing.*;
import java.text.*;
import java.util.*;

public class POFrame extends JFrame
{
public Panel leftPanel;
public Panel rightPanel;
public Panel topPanel;
public Panel paymentPanel;
public Panel submitCancelPanel;


// constructor
public POFrame()
{
super("Purchase Order");

setBounds(50,50,600,500);
setDefaultCloseOperation(EXIT_ON_CLOSE);
getContentPane().setLayout(new GridLayout(3,0));


leftPanel=new Panel();
rightPanel=new Panel();
topPanel=new Panel();
paymentPanel=new Panel();
submitCancelPanel=new Panel();

// Filling the TopPanel

leftPanel.setLayout(new GridLayout(4,1));
leftPanel.add(new Label("Date"));
Date today = new Date();
DateFormat df = DateFormat.getDateInstance(DateFormat.LONG,Locale.US);
String prntDate = df.format(today);
TextField dateText = new TextField();
dateText.setText(prntDate);
leftPanel.add(dateText);
leftPanel.add(new Label("ITEM CATEGORY"));
Choice item_category = new Choice();
item_category.addItem("Hardware");
item_category.addItem("Software");

// CategoryListener cl = new CategoryListener();
//item_category.addItemListener(cl);

leftPanel.add(item_category);


rightPanel.setLayout(new GridLayout(4,1));
rightPanel.add(new Label("ITEM DESCRIPTION"));
rightPanel.add(new TextArea());
rightPanel.add(new Label("ITEM COMPONENT"));

CompList cList = new CompList("Hardware");

rightPanel.add(cList);

topPanel.setLayout(new GridLayout(1,2));
topPanel.add(leftPanel);
topPanel.add(rightPanel);

paymentPanel.setLayout(new GridLayout(4,1));
paymentPanel.add(new Label("PAYMENT METHOD"));

CheckboxGroup cbg=new CheckboxGroup();
Checkbox cbx1=new Checkbox("Visa",false,cbg);
Checkbox cbx2=new Checkbox("MasterCard",false,cbg);
Checkbox cbx3=new Checkbox("American Express",false,cbg);
// paymentPanel.add(cbg);

paymentPanel.add(cbx1);
paymentPanel.add(cbx2);
paymentPanel.add(cbx3);



// Filling the submitCancelPanel

// add Buttons

Button CancelButton = new Button("Cancel");
Button SubmitButton = new Button("Submit");

CancelButton.setBackground(Color.blue);
SubmitButton.setBackground(Color.red);

submitCancelPanel.add(CancelButton);
submitCancelPanel.add(SubmitButton);


getContentPane().add(topPanel);
getContentPane().add(paymentPanel);
getContentPane().add(submitCancelPanel);
setVisible(true);


}


}

/* class CategoryListener implements ItemListener
{
public void itemStateChanged(ItemEvent ie)
{
Choice catgList = (Choice)(ie.getSource());
String catgChosen = catgList.getSelectedItem();
if (catgChosen.equals("Hardware"))
{
rightPanel.removeAll();
rightPanel.add(new Label("ITEM COMPONENT"));
CompList cList = new CompList("Hardware");
rightPanel.add(cList);
}
else
{
rightPanel.removeAll();
rightPanel.add(new Label("ITEM COMPONENT"));
CompList cList = new CompList("Hardware");
rightPanel.add(cList);
}
}
} */

Also, the program that i run to create the Frame is just this:
/* Program to create a window */
import java.awt.*;
import javax.swing.*;
public class POCreate
{
public static void main(String[] args)
{
POFrame pof = new POFrame();
}
}

[shree vijay]

Hi,
The CompList class in the above example is as follows:
I forgot to add that before:

import java.awt.*;

public class CompList extends List
{
String[] hComps = {"RAM","CDROM","MOTHERBOARD"};
String[] sComps = {"Windows","Weblogic","Flash"};
public CompList(String type)
{
super(3,false);

if (type.equals("Hardware"))
{
for (int i=0;i<hComps.length;i++)>
{
add(hComps[i]);
}
}
else
{
for (int i=0;i<sComps.length;i++)>
{
add(sComps[i]);
}
}
}
}

[shree vijay]

Hi,
The CompList class in the above example is as follows:
I forgot to add that before:

import java.awt.*;

public class CompList extends List
{
String[] hComps = {"RAM","CDROM","MOTHERBOARD"};
String[] sComps = {"Windows","Weblogic","Flash"};
public CompList(String type)
{
super(3,false);

if (type.equals("Hardware"))
{
for (int i=0;i<hComps.length;i++)>
{
add(hComps[i]);
}
}
else
{
for (int i=0;i<sComps.length;i++)>
{
add(sComps[i]);
}
}
}
}

[Randall Twede]

im not sure how much this will help. I have a Choice in my Applet named picts.
public class Farm extends java.applet.Applet implements ItemListener {
picts.addItemListener(this); //makes the applet the listener
//the method of the applet that handles the event
synchronized public void itemStateChanged(final java.awt.event.ItemEvent p1) {
selection = picts.getSelectedIndex();
Image im = this.getImage(this.getDocumentBase(),picts.getSelectedItem());
an.updateImage(im);
}

[This message has been edited by Randall Twede (edited November 29, 2000).]
[This message has been edited by Randall Twede (edited November 29, 2000).]