java AWT中的.add()在actionPerformed之后不起作用

import java.awt.*;
import java.awt.event.*;

public class MyFrame extends Frame implements ActionListener {
    private Button button;

    public MyFrame() {
        button = new Button("Click me");
        button.addActionListener(this);
        add(button);
    }

    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == button) {
            Label label = new Label("New Label");
            add(label);
            revalidate();
            repaint();
        }
    }

    public static void main(String[] args) {
        MyFrame frame = new MyFrame();
        frame.setLayout(new FlowLayout());
        frame.setSize(300, 200);
        frame.setVisible(true);
    }
}