Absolute Positioning

[Brian Winkler]

I have this test code I am trying with a panel that uses absolute positioning, but when I run the code, it doesn't like the setLayout(null) line. Can one of you please look at it and let me know what I have wrong? Thanks.

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

package test;
 
/*
 * 
 */
 
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
 
public class Test extends JFrame
{
    private JPanel panel;
    
    public void buildPanel() 
    {
        panel.setLayout(null);
        panel = new JPanel();
 
        JButton b1 = new JButton("MC");
        JButton b2 = new JButton("MR");
        JButton b3 = new JButton("MS");
        JButton b4 = new JButton("M+");
        JButton b5 = new JButton("M-");
 
        panel.add(b1);
        panel.add(b2);
        panel.add(b3);
        panel.add(b4);
        panel.add(b5);
 
        //Insets insets = pane.getInsets();
        //Dimension size = b1.getPreferredSize();
        b1.setBounds(5, 5, 42, 42);
        //size = b2.getPreferredSize();
        b2.setBounds(52, 5, 42, 42);
        //size = b3.getPreferredSize();
        b3.setBounds(99, 5, 42, 42);
        b4.setBounds(146, 5, 42, 42);
        b5.setBounds(193, 5, 42, 42);
    }
 
    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private Test() 
    {
        //Create and set up the window.
        
        JFrame frame = new JFrame("AbsoluteLayoutDemo");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
        //Set up the content pane.
        buildPanel();
        add(panel);
 
        //Size and display the window.
        setSize(400, 400);
        setVisible(true);
    }
 
    public static void main(String[] args) 
    {
        new Test();
    }

}

[Michael Dunn]

panel.setLayout(null);
panel = new JPanel();

reverse the lines

[Brian Winkler]

Michael Dunn wrote:panel.setLayout(null);
panel = new JPanel();

reverse the lines

ha, I just figured it out at the same time you answers that. Thank you.

One other question, I am trying to take that panel and insert it into a JFrame with a border layout as the SOUTH panel, but when I run the code, nothing shows. Should I be able to do this? or am I doing something wrong?

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

package test;
 
/*
 * 
 */
 
import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
 
public class Test extends JFrame
{
    private JPanel panel;
    
    public void buildPanel() 
    {
        panel = new JPanel();
        panel.setLayout(null);
        
        JButton b1 = new JButton("MC");
        JButton b2 = new JButton("MR");
        JButton b3 = new JButton("MS");
        JButton b4 = new JButton("M+");
        JButton b5 = new JButton("M-");
 
        //Insets insets = pane.getInsets();
        //Dimension size = b1.getPreferredSize();
        b1.setBounds(5, 5, 42, 42);
        //size = b2.getPreferredSize();
        b2.setBounds(52, 5, 42, 42);
        //size = b3.getPreferredSize();
        b3.setBounds(99, 5, 42, 42);
        b4.setBounds(146, 5, 42, 42);
        b5.setBounds(193, 5, 42, 42);
        
        panel.add(b1);
        panel.add(b2);
        panel.add(b3);
        panel.add(b4);
        panel.add(b5);
    }
 
    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private Test() 
    {
        //Create and set up the window.
        
        super("AbsoluteLayoutDemo");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new BorderLayout());
 
        //Set up the content pane.
        buildPanel();
        add(panel, BorderLayout.SOUTH);
 
        //Size and display the window.
        setSize(400, 400);
        setVisible(true);
    }
 
    public static void main(String[] args) 
    {
        new Test();
    }

}

[Michael Dunn]

because 'panel' is a null layout it has no
preferred size i.e. a preferred size (0,0)

BorderLayout uses the preferred size to
layout the components, so add
panel.setPreferredSize(new Dimension(400,100));
where 400,100 can be anything you want.
then use
frame.pack();
instead of
frame.setSize();

[Brian Winkler]

Michael Dunn wrote:because 'panel' is a null layout it has no
preferred size i.e. a preferred size (0,0)

BorderLayout uses the preferred size to
layout the components, so add
panel.setPreferredSize(new Dimension(400,100));
where 400,100 can be anything you want.
then use
frame.pack();
instead of
frame.setSize();

I love this site. This worked perfectly. Thanks again for your help!