Jslider, not appearing on My frame

Question

im trying to make my slider appear on my gui once i run my java project, here is what i >have, any help would be nice :)

so the menu bar appears, the menu shapes appears, and the 3 shapes appear too, i just cant >get the slider to appear on at the bottom of the box

class assignment

package assignment;

public class Assignment {

public static void main(String[] args) {
    
MyFrame pane = new MyFrame();  
   
pane.setVisible(true);
pane.setSize(400,400);

class MyFrame

package assignment;

import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;

public class MyFrame extends javax.swing.JFrame {

/**
 * Creates new form MyFrame
 */
public MyFrame() {
initComponents();
    
// Create the menu
JMenuBar topMenu = new JMenuBar();
this.setJMenuBar(topMenu);
    
//create the menu button "shapes"
JMenu shapes = new JMenu("Shapes");
topMenu.add(shapes);
//Create the 3 shapes for the menu
JMenuItem square = new JMenuItem("Square");
JMenuItem circle = new JMenuItem("Circle");        
JMenuItem triangle = new JMenuItem("Triangle");
    
//add shapes to menu
shapes.add(circle);
shapes.add(triangle);
shapes.add(square);
    
//add the menu
setJMenuBar(topMenu);
    
    
MyControlPanel pane = new MyControlPanel();
this.add(pane);
    
    
}

/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 400, Short.MAX_VALUE)
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 300, Short.MAX_VALUE)
    );

    pack();
}// </editor-fold>

/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.

    try {
        for (javax.swing.UIManager.LookAndFeelInfo info :          javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(MyFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(MyFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(MyFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(MyFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        @Override
        public void run() {
        new MyFrame().setVisible(true);
        }
    });
    
    
}
// Variables declaration - do not modify
// End of variables declaration

}

class MyControlPanel

package assignment;

import javax.swing.JSlider;
import javax.swing.JTextField;


public class MyControlPanel extends javax.swing.JPanel {

/**
 * Creates new form MyControlPanel
 */
public MyControlPanel() {
initComponents();

JSlider slider = new JSlider();
slider.setMajorTickSpacing(10); 
slider.setPaintLabels(true); 
slider.setPaintTicks(true); 
 
JTextField boundary_length = new JTextField("Boundary Length");
JTextField area = new JTextField("Area");
    
 
this.add(slider);
this.add(area);
this.add(boundary_length);
    
}

/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
    this.setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 400, Short.MAX_VALUE)
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 300, Short.MAX_VALUE)
    );
}// </editor-fold>
// Variables declaration - do not modify
// End of variables declaration

}

1. Avoid form designers until you understand what the various layout managers are doing. 2. Use a different layout manager, try `FormLayout` as a test. Have a look at [A Visual Guide to Layout Managers](http://docs.oracle.com/javase/tutorial/uiswing/layout/visual.html) and [Using Layout Managers](http://docs.oracle.com/javase/tutorial/uiswing/layout/using.html) for more information — MadProgrammer, Oct 20 '12 at 01:10
i understand that but i'm sure i'm missing some code some where? — john, Oct 20 '12 at 01:24
@Mad Why `FormLayout` as opposed to (e.g.) `FlowLayout`? Not that I have anything against `FormLayout`, it is very useful, just not a J2SE inbuilt layout. — Andrew Thompson, Oct 20 '12 at 01:27
@AndrewThompson *doh*, yes, that should be `FlowLayout`, it's being a fun 3 days of sick wife :P — MadProgrammer, Oct 20 '12 at 01:28
@MadProgrammer I could still use a bit of help, i Don't understnad why my slider isnt appearing — john, Oct 20 '12 at 01:29
@StevenMcilhone Have you tried using `FlowLayout` to confirm the component appears? — Andrew Thompson, Oct 20 '12 at 01:31
@AndrewThompson im still new to java, im unsure what i have to change for that :( — john, Oct 20 '12 at 01:33
@Steven: you're just adding the JSlider to the GUI without respecting the layout managers at all. I second what everyone else is saying. Go to the [layout manager tutorial](http://docs.oracle.com/javase/tutorial/uiswing/layout/index.html) and read through it, and get rid of your generated code. You need to understand what layouts do and how to use them before anyone can help you. — Hovercraft Full Of Eels, Oct 20 '12 at 01:33
Remove the entire content of `initCoponent()` and replace it with `this.setLayout(new FlowLayout());` or `this.setLayout(new GridLayout(1,0));`. In fact, try both. — Andrew Thompson, Oct 20 '12 at 01:35
I have removed the generated code, and it works, thanks for that help, i'l look into that tut. thanks everyone — john, Oct 20 '12 at 01:36

score 2 · Accepted Answer · answered Oct 20 '12 at 01:37

What you're missing is an understanding of the GroupLayout

If I do this

public MyControlPanel() {
    initComponents();

    JSlider slider = new JSlider();
    slider.setMajorTickSpacing(10);
    slider.setPaintLabels(true);
    slider.setPaintTicks(true);

    JTextField boundary_length = new JTextField("Boundary Length");
    JTextField area = new JTextField("Area");

    setLayout(new FlowLayout());

    this.add(slider);
    this.add(area);
    this.add(boundary_length);

}

I get this...

enter image description here

All I did was change the layout manager to FlowLayout. No offense, but GroupLayout isn't suppose to be created by hand as is really suppose to be used with form editors.

Jslider, not appearing on My frame

1 Answers1