Thread: dynamically adding panels...but getteng next panel after minimizing and maximizing the window only why?

import javax.swing.*;
import java.io.*;
import java.awt.*;
import java.awt.event.*;
class sacreate extends JFrame implements ActionListener
{
 
JLabel l1,l2,l3,l4,a,b,c;
Container pane;
JPanel p1,p2,p3;
JTextField t1;
JComboBox c1,c2;
JCheckBox m1;
JButton b1,b2,b3;
public sacreate()
{
try
{
pane=getContentPane();
l1=new JLabel("FieldName"); 
a=new JLabel("                                       ");
l2=new JLabel("DataType");
b=new JLabel("                 ");
l3=new JLabel("NotNull");
c=new JLabel("        ");
l4=new JLabel("Null");
t1=new JTextField(15);
c1=new JComboBox();
c1.addItem("VARCHAR");
c1.addItem("INTEGER");
c1.addItem("CHARACTER");
c2=new JComboBox();
c2.addItem("PrimaryKey");
c2.addItem("ForignKey");
m1=new JCheckBox();
b3=new JButton("Done");
b1=new JButton("+");
b2=new JButton("-");
p1=new JPanel();
p2=new JPanel();
p3=new JPanel();
p1.add(l1);
p1.add(a);
p1.add(l2);
p1.add(b);
p1.add(l3);
p1.add(c);
p1.add(l4);
p2.add(t1);
p2.add(c1);
p2.add(c2);
p2.add(m1);
p2.add(b3);
p2.add(b1);
p2.add(b2);
p3.add(p1);
p3.add(p2);
pane.add(p3);
p1.setLayout(new FlowLayout(FlowLayout.LEFT));
p2.setLayout(new FlowLayout(FlowLayout.LEFT));
p3.setLayout(new BorderLayout());
p3.add(p1,BorderLayout.NORTH);
p3.add(p2,BorderLayout.SOUTH);
setLayout(new FlowLayout());
b1.addActionListener(this);
b2.addActionListener(this);
}
catch(Exception e)
{
System.out.println(e.toString());
}
}
public void actionPerformed(ActionEvent ae)
  {
JPanel p = new JPanel();
Dimension size=p.getSize();
System.out.println(size);
p.setPreferredSize(new Dimension(1600,35));
JTextField t=new JTextField(15);
JComboBox m=new JComboBox();
m.addItem("VARCHAR");
m.addItem("INTEGER");
m.addItem("CHARACTER");
JComboBox n=new JComboBox();
n.addItem("PrimaryKey");
n.addItem("ForignKey");
JCheckBox c=new JCheckBox();
JButton o=new JButton("Done");
JButton r=new JButton("+");/*after pressing this '+' button i have to get next panel with some components but by clicking '+' and by minimizing and maximizing the window only i am able to see the next panel why?*/
r.addActionListener(this);
JButton q=new JButton("-");
q.addActionListener(this);
if(ae.getActionCommand()=="+")
 {
pane.add(p);
p.add(t);
p.add(m);
p.add(n);
p.add(c);
p.add(o);
p.add(r);
p.add(q);
p.revalidate(); 
p.setLayout(new FlowLayout());
}
if(ae.getActionCommand()=="-")
{
/*p.remove(t);
p.remove(m);
p.remove(n);
p.remove(c);
p.remove(o);
p.remove(r);
p.remove(q);*/
 
pane.remove(p);
pane.revalidate();
pane.repaint();
}
}
public static void main(String args[])
{
sacreate a=new sacreate();
a.setSize(300,300);
a.setVisible(true);
a.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
a.setLocationRelativeTo(null);
}
}

thanx for saying i did it...

i kept try catch blocks to caught the errors if any.....if it is removed also there will be no errors...but if == is not kept i am getting an error...= is used for assigning a value and where as == is used to compare to values....

 
import javax.swing.*;
import java.io.*;
import java.awt.*;
import java.awt.event.*;
class sacreate extends JFrame implements ActionListener
{
 
JLabel l1,l2,l3,l4,a,b,c;
Container pane;
JPanel p1,p2,p3;
JTextField t1;
JComboBox c1,c2;
JCheckBox m1;
JButton b1,b2,b3;
public sacreate()
{
 
pane=getContentPane();
l1=new JLabel("FieldName"); 
a=new JLabel("                                       ");
l2=new JLabel("DataType");
b=new JLabel("                 ");
l3=new JLabel("NotNull");
c=new JLabel("        ");
l4=new JLabel("Null");
t1=new JTextField(15);
c1=new JComboBox();
c1.addItem("VARCHAR");
c1.addItem("INTEGER");
c1.addItem("CHARACTER");
c2=new JComboBox();
c2.addItem("PrimaryKey");
c2.addItem("ForignKey");
m1=new JCheckBox();
b3=new JButton("Done");
b1=new JButton("+");
b2=new JButton("-");
p1=new JPanel();
p2=new JPanel();
p3=new JPanel();
p1.add(l1);
p1.add(a);
p1.add(l2);
p1.add(b);
p1.add(l3);
p1.add(c);
p1.add(l4);
p2.add(t1);
p2.add(c1);
p2.add(c2);
p2.add(m1);
p2.add(b3);
p2.add(b1);
p2.add(b2);
p3.add(p1);
p3.add(p2);
pane.add(p3);
p1.setLayout(new FlowLayout(FlowLayout.LEFT));
p2.setLayout(new FlowLayout(FlowLayout.LEFT));
p3.setLayout(new BorderLayout());
p3.add(p1,BorderLayout.NORTH);
p3.add(p2,BorderLayout.SOUTH);
setLayout(new FlowLayout());
b1.addActionListener(this);
b2.addActionListener(this);
}
 
 
 
public void actionPerformed(ActionEvent ae)
  {
 
 JTextField t;
 JComboBox m,n;
 JCheckBox c;
 JButton o,r,q;
 JPanel p;
p = new JPanel();
Dimension size=p.getSize();
System.out.println(size);
p.setPreferredSize(new Dimension(1600,35));
t=new JTextField(15);
m=new JComboBox();
m.addItem("VARCHAR");
m.addItem("INTEGER");
m.addItem("CHARACTER");
n=new JComboBox();
n.addItem("PrimaryKey");
n.addItem("ForignKey");
c=new JCheckBox();
o=new JButton("Done");
r=new JButton("+");
r.addActionListener(this);
q=new JButton("-");
q.addActionListener(this);
if(ae.getActionCommand()=="+")
{
pane.add(p);
p.add(t);
p.add(m);
p.add(n);
p.add(c);
p.add(o);
p.add(r);
p.add(q);
p.revalidate(); 
p.setLayout(new FlowLayout());
}
}
public static void main(String args[]) 
{
 
SwingUtilities.invokeLater(new Runnable() 
{
public void run() 
{
sacreate a=new sacreate();
a.setSize(1600,800);
a.setVisible(true);
a.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
a.setLocationRelativeTo(null);
}
});
}
}