Calling a JPanel in a JFrame of another Class

Question

I have created a class with one JPanel which will be used for the CardLayout, this works fine if I remove the comment // which has the window size at the bottom of the code. It will run that way and everything functions perfectly. However when I try to call it from another class which has a JFrame in it, it doesn't work.

CardDemo.java:

import java.awt.CardLayout;
import java.awt.Color;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import java.awt.*;

public class CardDemo extends JPanel implements ListSelectionListener {

CardLayout cl;
JPanel p1, p2, p3, p4, p5;
JList l1;


public CardDemo(){

    p1 = new JPanel();
    p1.setBackground(Color.red);   //the top panel

    String[] list1 = { "One", "Two", "Three"};
    l1 = new JList(list1);
    l1.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
    l1.addListSelectionListener(this);

    p1.add(l1);

    p2 = new JPanel();
    p2.setBackground(Color.blue);  //bottom panel - we never actually see this

    cl = new CardLayout();
    p2.setLayout(cl);


    p3 = new JPanel();
    p3.setBackground(Color.green);
    p4 = new JPanel();
    p4.setBackground(Color.yellow); 
    p5 = new JPanel();
    p5.setBackground(Color.cyan);


    p2.add(p3, "One");
    p2.add(p4, "Two");
    p2.add(p5, "Three");

    //this.setSize(500,400);
   //this.setVisible(true);
   this.setLayout(new GridLayout(2,2));
   this.add(p1);
   this.add(p2);

}

/** The actionPerformed method handles button clicks
 */
public void valueChanged(ListSelectionEvent e) {
    String listLabel = (String) ((JList)e.getSource()).getSelectedValue();    //get the label of the button that was clicked
    cl.show(p2, listLabel);             //use the label to display the relevant panel
}
}

Test.java

import javax.swing.*;
import java.awt.*;

public class Test extends JFrame
{

public Test()
{
  JFrame frame = new JFrame("CardLayoutDemo");
  frame.setDefaultCloseOperation(EXIT_ON_CLOSE);

  CardDemo b = new CardDemo();
  b.add(frame);

  frame.pack();
  frame.setVisible(true);
}


}

Everything compiles just fine, but when I run Test.java I get the following error:

java.lang.IllegalArgumentException: adding a window to a container (in java.awt.Container)

What is it that I am doing wrong as I can't seem to pinpoint it.

Regarding `"PLEASE DO NOT APPROVE THIS AS I DO NOT WANT THIS KEPT ON HERE, I WISH TO DELETE THIS AFTER AS I DON'T WANT MY WORK TO REMAIN ON THE NET, MUCH APPRECIATED."` -- you can't do this. If it is posted here it should remain here as questions posted here are not for your benefit alone but are for all future visitors with similar problems. I have deleted this from your question so that there is no doubt. — Hovercraft Full Of Eels, Nov 03 '13 at 13:39
Question rolled back to previous state. Please don't alter your code without explanation. — Hovercraft Full Of Eels, Nov 03 '13 at 13:47
No one is going to steal your code. And regardless, I stand by my previous comment, that these questions are not for the asker's benefit only but are mainly for future visitors to this site. — Hovercraft Full Of Eels, Nov 03 '13 at 13:54

score 1 · Accepted Answer · edited Nov 03 '13 at 15:10

1

You need to change

b.add(frame);

to

frame.add(b);

edited Nov 03 '13 at 15:10

Eel Lee

3,513
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answered Nov 03 '13 at 13:38

Mengjun

3,159
1
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score 0 · Answer 2 · answered Nov 03 '13 at 13:37

You're adding your JFrame to your JPanel. It should be the other way around. The frame variable refers to a JFrame which is a top level window. This is the top level container of all your components, and so you'll want to add components to it, not the other way around.

Calling a JPanel in a JFrame of another Class

2 Answers2