I'm trying to use a List but I get an error I can't debug!

[Sorc.Polgara]

Ok, I've spent a couple hours trying to figure out what this error I'm getting means and how to fix it.  I've surfed google trying to see if I can get any hints on what the problem might be but I've been unsuccessful!  Please help.

Here is the error message:

Exception in thread "main" java.lang.IllegalArgumentException: cannot add to layout: constraints must be a GridBagConstraint
        at java.awt.GridBagLayout.addLayoutComponent(GridBagLayout.java:608)
        at java.awt.Container.addImpl(Container.java:1058)
        at java.awt.Container.add(Container.java:899)
        at WindowLayout.makeList(WindowLayout.java:88)
        at WindowLayout.makeLayout(WindowLayout.java:101)
        at WindowLayout2.getWindow(WindowLayout2.java:60)
        at Tester.main(Tester.java:11)

Here is the Code:

Code Select Expand


import javax.swing.*;
import java.awt.*;
import java.awt.BorderLayout;
import java.util.*;
import java.applet.Applet;


public class WindowLayout2 extends Applet
{
private DefaultListModel listModel;
private JList list;

public WindowLayout2(){
//
setLayout(new BorderLayout());
}

protected void makeList(GridBagLayout gridbag, GridBagConstraints c)
{
JList list = new JList();

gridbag.setConstraints(list, c);

                listModel = new DefaultListModel();
                listModel.addElement("Holy Light");
                listModel.addElement("Denial");
                listModel.addElement("Teleport");
                listModel.addElement("Chakra Magic");

                list = new JList(listModel);
                list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
                list.setSelectedIndex(0);
                list.setVisibleRowCount(-1);
                JScrollPane listScrollPane = new JScrollPane(list);

                add(listScrollPane, BorderLayout.CENTER);
add(list);
}

public void makeLayout()
{
GridBagLayout gridbag = new GridBagLayout();
GridBagConstraints c = new GridBagConstraints();

setFont(new Font("Helvetica", Font.PLAIN, 14));
setLayout(gridbag);

c.weightx = 1.0;
makeList(gridbag, c);

setSize(300, 100);
}

public JFrame getWindow()
{
JFrame f = new JFrame("List Test");
WindowLayout2 ex1 = new WindowLayout2();

                ex1.makeLayout();                        // Line 60

f.add("Center", ex1);
f.pack();
f.setSize(f.getPreferredSize());
f.show();

return f;
}
}


Here is the Tester program:

Code Select Expand


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

public class Tester{
    public static void main(String[] args)
    {
    WindowLayout2 windowLayout = new WindowLayout2();
    JFrame frame = new JFrame();
        frame = windowLayout.getWindow();           // Line 10
    }
}



Please help.

[Kp]

According to the backtrace, your closing brace on main is causing a problem.  Have you tried disabling it?

[Sorc.Polgara]

According to the backtrace, your closing brace on main is causing a problem.  Have you tried disabling it?

wtf, I don't see how my closing brace on the main function in the tester would be causing a problem... I need that closing brace there.

[Dynobird]

You can't instantiate List, it's abstract. That's your error. Try ArrayList or LinkedList, they're some of its derived concrete classes. Or try using my classes for your lists, posted here .