按下JButton后将JTable放在JPanel上

Question

When I run this code, the button shows up on the JPanel but once I click the button, nothing happens. Any suggestions on where I'm going wrong here? Sorry if it's really simple. I'm fairly new when it comes to GUIs.

final JPanel card3 = new JPanel();
//Tetris setup
JButton startGame = new JButton("START GAME");
card3.setLayout(new GridBagLayout());
GridBagConstraints gbc2 = new GridBagConstraints();
gbc.gridx = 0;
gbc.gridy = 0;
gbc.insets = new Insets(2,2,2,2);
card3.add(startGame, gbc2);
gbc.gridy = 1;
startGame.addActionListener(new ActionListener() {          
    @Override
    public void actionPerformed(ActionEvent e) {
        Tetris game = new Tetris();
        JTable table = new JTable(game.getNumRows(), game.getNumCols());
        card3.add(table);
    }
});

Answer 1

Normally you would add the table to a JScrollPane and then add the scrollpane to the panel. This way you will automatically get the table header to appear.

When you add a component to a visible GUI you need code like:

panel.add( scrollPane );
panel.revalidate();

This will cause the layout manager to be invoked to it can lay out all the components again.