Problem with Dynamic GUI in NB

Question

Hi all!
i'm a noob in GUI programming, BTW i created a stand alone class (read app) that can draw a Line Graph.
Let's name this class Drawer.
Drawer extends JPanel, anyway when in my NB project i try to add the Drawer to a JPanel doing
// i added the following code in the initComponents()
Drawer d = new Drawer();
jPanel2.add(d); // jPanel2 is created by Drag & Drop in the IDEit doesn't happen anything, nothing is displayed, neither if i call the methods:
pack();
repaint();
updateUI();
suggestions?
thanks everyone!
Gio-Kun

Answer 1

Here i post the full example code:
this is the main class of the project:
Frame.java
package drawer;
import java.awt.Point;
public class Frame extends javax.swing.JFrame {
    /** Creates new form Frame */
    public Frame() {
        drawer = new Drawer();
        init();
    /*this is the init component modified by me to add the drawer object to the panel*/
    private void init(){
        panel = new javax.swing.JPanel();
        addButton = new javax.swing.JButton();
        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        yField = new javax.swing.JTextField();
        xField = new javax.swing.JTextField();
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        panel.setBorder(new javax.swing.border.LineBorder(new java.awt.Color(0, 0, 0), 1, true));
        panel.setPreferredSize(new java.awt.Dimension(300, 200));
        org.jdesktop.layout.GroupLayout panelLayout = new org.jdesktop.layout.GroupLayout(panel);
        panel.setLayout(panelLayout);
        panelLayout.setHorizontalGroup(
            panelLayout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(0, 298, Short.MAX_VALUE)
        panelLayout.setVerticalGroup(
            panelLayout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(0, 198, Short.MAX_VALUE)
        addButton.setText("Add");
        addButton.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseClicked(java.awt.event.MouseEvent evt) {
                addButtonMouseClicked(evt);
        jLabel1.setText("X");
        jLabel2.setText("Y");
        yField.setText("int y");
        yField.setPreferredSize(new java.awt.Dimension(75, 22));
        xField.setText("int x");
        xField.setPreferredSize(new java.awt.Dimension(75, 22));
        org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                    .add(layout.createSequentialGroup()
                        .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                            .add(panel, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                            .add(layout.createSequentialGroup()
                                .add(35, 35, 35)
                                .add(jLabel1)
                                .add(96, 96, 96)
                                .add(jLabel2)))
                        .add(20, 20, 20))
                    .add(org.jdesktop.layout.GroupLayout.TRAILING, layout.createSequentialGroup()
                        .add(xField, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                        .addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED, 30, Short.MAX_VALUE)
                        .add(yField, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                        .addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED)
                        .add(addButton)
                        .add(95, 95, 95))))
        layout.setVerticalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(panel, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED, 24, Short.MAX_VALUE)
                .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.BASELINE)
                    .add(jLabel1)
                    .add(jLabel2))
                .addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED)
                .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.BASELINE)
                    .add(addButton)
                    .add(yField, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                    .add(xField, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE))
                .add(12, 12, 12))
        /*Here i add the drawer object to the panel*/
        panel.add(drawer);
        /*i revalidate and repaint the panel*/
        panel.revalidate();
        panel.repaint();
        /*validation of the frame*/
        this.validate();
        this.pack();
    /*This method handles the insertion of new points on the Graph*/
    private void addButtonMouseClicked(java.awt.event.MouseEvent evt) {                                      
        Point p;
        int x = 0,y = 0;
        x = Integer.parseInt(xField.getText());
        y = Integer.parseInt(yField.getText());
        p = new Point(x,y);
        System.out.println(p.toString());
        drawer.addPoint(p);
     * @param args the command line arguments
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                Frame frame;
                frame = new Frame();
                frame.setResizable(false);
                frame.setVisible(true);
    // Variables declaration - do not modify                    
    private javax.swing.JButton addButton;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JPanel panel;
    private javax.swing.JTextField xField;
    private javax.swing.JTextField yField;
    // End of variables declaration                  
    private Drawer drawer;
}here there's the other class of the project:
the task of this class is painting the graph.
you can try separately by uncommenting the main.
Drawer.java
package drawer;
import java.util.*;
import java.awt.*;
import javax.swing.*;
import java.lang.Thread;
public class Drawer extends JPanel{
     LinkedList<Point> pointList;
     Graphics g;
     public Drawer(){
          pointList = new LinkedList<Point>();
          setPreferredSize(new Dimension(290,190));
          setBackground(Color.WHITE);
                /*to be used if this class is used as a stand alone application*/
                //pointList.add(new Point(0,0));
          //pointList.add(new Point(30,50));
          //pointList.add(new Point(50,150));
     public void paintComponent(Graphics g){
          super.paintComponent(g);
          g.setColor(Color.BLACK);
          Point start, end;
          //System.out.println(pointList.size());
          start = (Point)pointList.get(0);
          for(int i=1;i<pointList.size();i++){
               end = (Point)pointList.get(i);
               //System.out.println("Start: "+start.toString()+"\tEnd: "+end.toString());
               g.drawLine(start.x,290-start.y,end.x,190-end.y);
               start = end;
        /*this method is called only if you use this class as stand alone application*/
     public void addItems(){
          pointList.add(new Point(70,255));
                pointList.add(new Point(70,352));
                pointList.add(new Point(80,255));
                pointList.add(new Point(110,255));
                repaint();
        public void addPoint(Point p){
            pointList.add(p);
            System.out.println("Successfully added point:"+p.toString()+"to the pointList");
            repaint();
     public static void main(String[] args){
          JFrame frame = new JFrame("Line drawer");
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          Drawer d= new Drawer();
          frame.getContentPane().add(d);
          frame.setResizable(false);
          frame.pack();
          frame.setVisible(true);
          Thread t = new Thread();
          try{
               t.sleep(3000);
          catch(Exception e){}
          d.addItems();
}hope this clarify the problem.
thanks in advance.
sorry camickr, i clicked on the wrong forum but i hope this will be the last question on this problem.
thanks everyone!