Reconstructing JPanel by an event

Question

Hai there'
i have an app , when a button clicked it should add a set of components in row wise in JPanel which is in a JScrollPane.
I have problem that JPanel losts the previous components at each click.How could i make the Viewport to show components added previously.

Answer 1

The choice of layout manager can be crucial.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class AddingComponents extends JPanel
    GridBagConstraints gbc;
    public AddingComponents()
        setLayout(new GridBagLayout());
        gbc = new GridBagConstraints();
        gbc.insets = new Insets(5,5,5,5);
        gbc.weightx = 1.0;
        gbc.weighty = 1.0;
    private JPanel getUIPanel()
        JButton add = new JButton("add components");
        add.addActionListener(new ActionListener()
            int count = 0;
            public void actionPerformed(ActionEvent e)
                for(int j = 0; j < 4; j++)
                    if((j + 1) % 4 == 0)
                        gbc.gridwidth = gbc.REMAINDER;
                    else
                        gbc.gridwidth = 1;
                    add(new JButton("button " + ++count), gbc);
                revalidate();
        JPanel panel = new JPanel();
        panel.add(add);
        return panel;
    public static void main(String[] args)
        AddingComponents ac = new AddingComponents();
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(ac.getUIPanel(), "North");
        f.getContentPane().add(new JScrollPane(ac));
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
}