Problem of dynamically change components in Applet

Question

Hello, All,
I need to dynamically change Applet components. For example, remove a button, and replace it with drop down list etc. I use remove and add methods to perform the task. But it does not work. Applet just become blank. And repaint does not help either. Any of you know how to solve the problem. I will really apprecation that.
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Answer 1

/*    <applet code="AddAndRemove" width="400" height="300"></applet>
*  use: >appletviewer AddAndRemove.java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class AddAndRemove extends JApplet {
  ButtonListener buttonListener = new ButtonListener();
  JButton
    addButton,
    removeButton;
  JPanel centerPanel;
  JLabel statusLabel;
  GridBagConstraints gbc;
  int buttonCount = 0;
  public void init() {
    addButton = new JButton("add");
    removeButton = new JButton("remove");
    addButton.addActionListener(buttonListener);
    removeButton.addActionListener(buttonListener);
    JPanel northPanel = new JPanel();
    northPanel.add(addButton);
    northPanel.add(removeButton);
    centerPanel = new JPanel(new GridBagLayout());
    centerPanel.setBackground(Color.yellow);
    gbc = new GridBagConstraints();
    gbc.weightx = 1.0;
    gbc.weighty = 1.0;
    gbc.gridwidth = gbc.REMAINDER;
    statusLabel = new JLabel(" ", JLabel.CENTER);
    Container cp = getContentPane();
    cp.setLayout(new BorderLayout());
    cp.add(northPanel, "North");
    cp.add(new JScrollPane(centerPanel), "Center");
    cp.add(statusLabel, "South");
  private class ButtonListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
      JButton button = (JButton)e.getSource();
      if(button == addButton) {
        centerPanel.add(new JButton("Button " + ++buttonCount), gbc);
        // JComponent method
        centerPanel.revalidate();
        Component[] components = centerPanel.getComponents();
        statusLabel.setText("Currently " + components.length + " buttons showing");
      if(button == removeButton) {
        Component[] components = centerPanel.getComponents();
        if(components.length == 0)
          return;
        centerPanel.remove(components[components.length - 1]);
        // container method
        centerPanel.validate();
        // comment this out to see what happens without it
        centerPanel.repaint();
        statusLabel.setText("Currently " + (components.length - 1) + " buttons showing");
  public static void main(String[] args) {
    JFrame f = new JFrame("Add And Remove Applet");
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JApplet applet = new AddAndRemove();
    f.getContentPane().add(applet);
    f.setSize(400,300);
    f.setLocation(400,300);
    applet.init();
    applet.start();
    f.setVisible(true);
}