JButton wont show components

I want to make a simple Frame that would show a text field if I click on one button and would show a JLabel if I click on the other, but its not working and I'm not sure why?

I tried setting the variables to public but the result was the same, I also tried another commands in the button commands and it worked like showMessageDialog so I'm confused why it wont work

import java.awt.*;
import javax.swing.*;


public class CheckBoxFrame extends JFrame
{
    private JTextField textField1;
    private JLabel label1;
    private JButton txt;
    private JButton label;
    public CheckBoxFrame()
    {

        super ("JCheckBox Test" );
        textField1= new JTextField ("Text Field 1", 20 );
        textField1.setFont ( new Font ("Serif", Font.PLAIN,14));
        add(textField1);
        textField1.setVisible(false);

        label1 = new JLabel("Label1", JLabel.CENTER);
        add(label1);
        label1.setVisible(false);

        txt = new JButton ("Text Field");
        ButtonHandler b1 = new ButtonHandler();
        txt.addActionListener(b1);
        add(txt);

        label = new JButton ("label ");
        add(label);

        setLayout( new FlowLayout() );
        setVisible(true);
        setSize(400,400);

    }


    private class ButtonHandler implements ActionListener
    {
        public void actionPerformed   (ActionEvent a)
        {
            if (a.getSource() == txt)
            {
                label1.setVisible(false);
                textField1.setVisible(true);

            }

            if (a.getSource() == label)
            {
                label1.setVisible(true);
                textField1.setVisible(false);

            }
        }
    }



}