Line in a JLabel that disappear when adding to a new frame

Question

Hi,
I have the main frame (SampleFrame), where I put a JPanel with CardLayout, I want when I click on a button, a new JPanel (SamplePanel) is shown.
The problem is this new JPanel shows a picture (a line in a JLabel), the poblem is the picture does not appear...
The code is the following:
package sample;
//Main Class
public class Main {
    public static void main(String[] args) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new SampleFrame().setVisible(true);
//SampleFrame
package sample;
import  javax.swing.JPanel;
import javax.swing.*;
import java.awt.*;
public class SampleFrame extends javax.swing.JFrame {
    private SamplePanel samplePanel;
    private boolean flag;
     /** Creates new form SampleFrame */
    public SampleFrame() {
        initComponents();
        flag=false;
        samplePanel = new SamplePanel();
        jPanel1.add(samplePanel,"sample");
    /** 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.
    // <editor-fold defaultstate="collapsed" desc=" Generated Code ">                         
    private void initComponents() {
        jPanel1 = new javax.swing.JPanel();
        jButton1 = new javax.swing.JButton();
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        jPanel1.setLayout(new java.awt.CardLayout());
        jButton1.setText("OK");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
        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()
                .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                    .add(layout.createSequentialGroup()
                        .addContainerGap()
                        .add(jPanel1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 189, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE))
                    .add(layout.createSequentialGroup()
                        .add(81, 81, 81)
                        .add(jButton1)))
                .addContainerGap(org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        layout.setVerticalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(jPanel1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 182, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED, 19, Short.MAX_VALUE)
                .add(jButton1)
                .addContainerGap())
        pack();
    }// </editor-fold>                       
    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                        
// TODO add your handling code here:
        CardLayout cl = (CardLayout)(jPanel1.getLayout());
        cl.show(jPanel1, "sample");
        flag=true;
      /*  this.setVisible(false);
        this.setVisible(true);*/
     public void paint(Graphics g)
        super.paint(g);
        if(flag)samplePanel.ReDraw();
    public void printAll(Graphics g)
        super.printAll( g);
        if(flag)samplePanel.ReDraw();
    // Variables declaration - do not modify                    
    private javax.swing.JButton jButton1;
    private javax.swing.JPanel jPanel1;
    // End of variables declaration                  
//SamplePanel
package sample;
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
public class SamplePanel extends javax.swing.JPanel {
    /** Creates new form SamplePanel */
    public SamplePanel() {
        initComponents();
    /** 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.
    // <editor-fold defaultstate="collapsed" desc=" Generated Code ">                         
    private void initComponents() {
        jLabel1 = new javax.swing.JLabel();
        org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(this);
        this.setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(jLabel1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 150, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        layout.setVerticalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(jLabel1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 150, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
    }// </editor-fold>                       
     public void paint(Graphics g)
        super.paint(g);
        ReDraw();
    public void printAll(Graphics g)
        super.printAll( g);
        ReDraw();
    public void ReDraw()
        Graphics g = jLabel1.getGraphics();
        g.drawLine(0,0,100,100);
    // Variables declaration - do not modify                    
    private javax.swing.JLabel jLabel1;
    // End of variables declaration                  
}I have discovered that with the comment lines in SampleFrame (method jButton1ActionPerformed):
/*  this.setVisible(false);
this.setVisible(true);*/works properly, but I dont like this way...
Can anyone helps me? Thanks ;)

Answer 1

Hi again crwood!!
Okay, you're taking the content pane, a Container, from a top�level container (you mentioned a frame, "oldFrame"). And this container contains some JLabels which have lines drawn in them. You want to add this container to a card in a Cardlayout. Okay, so far so good.
That�s exactly what I want ;).
So (using your code):
I have the panel:
class SP extends JPanel {
    private int x1;
    private int y1;
    private int x2;
    private int y2;
    private Color color;
     private JLabel label;
    public SP(int x1, int y1, int x2, int y2, Color c) {
        this.x1 = x1;
        this.y1 = y1;
        this.x2 = x2;
        this.y2 = y2;
        color = c;
        setLayout(new BorderLayout());
        label =new JLabel();
        add(label);
    protected void paintComponent(Graphics g) {
                super.paintComponent(g);
          label.getGraphics().setColor(color);
          label.getGraphics().drawLine(x1, y1, x2, y2);
    public Dimension getPreferredSize() {
        return new Dimension(300, 200);
}And the main frame:
public class SF extends JFrame {
    private JPanel jPanel1;
    public SF() {
        // Initialize components.
        jPanel1 = new JPanel(new CardLayout());
        jPanel1.add(new SP(10,10,100,100,Color.red), "sample 1");
        jPanel1.add(new SP(50,150,200,50,Color.blue), "sample 2");
        JButton jButton1 = new JButton("OK");
        jButton1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent evt) {
                CardLayout cl = (CardLayout)(jPanel1.getLayout());
                cl.next(jPanel1);
        JPanel south = new JPanel();
        south.add(jButton1);
        // Configuration and assemble JFrame.
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        add(jPanel1);   // Default center section.
        add(south, "Last");
        pack();
        setLocation(200,200);
        setVisible(true);
    public static void main(String[] args) {
        new SF();
}The problem is I cant see the black line...
(I am able to see it by moving the window until hide part of it)