How to set the component's size inside a GridBagLayout

Question

As I've read, it's really hard to treat to resize components inside GridLayout and GrigBagLayout. In my case, I have a GridBagLayout with 2 columns and 2 rows. In the first row there are 2 labels and in the second row there are 2 components (type Tablero) which extend JTable.

My problem is, I can't make these 2 JTables fill the JFrame until its bottom. I've tried setSize(), setPreferredSize(), setBounds()... but they don't work at all. I've also tried to do it by constraints.fill = GridBagConstraints.VERTICAL/SOUTH/CENTER... but I get absolutly nothing. I've also tried to set the size of the JPanel inside of the JFrame, but it doesn't work...

This is my code:

public static void main(String[] args)
{

    JFrame pantalla = new JFrame();

    pantalla.getContentPane().setLayout(new GridBagLayout());
    GridBagConstraints constraints = new GridBagConstraints();

    JLabel tab1Label = new JLabel("Tablero 1");
    JLabel tab2Label = new JLabel("Tablero 2");

    Tablero tablero1 = new Tablero();
    Tablero tablero2 = new Tablero();
    tablero1.setPreferredSize(new Dimension(400,400));
    tablero1.setBounds(0, 0, 400, 400);

    tablero1.setBorder(new LineBorder(Color.gray, 2));

    constraints.gridx = 0;
    constraints.gridy = 0;
    constraints.gridwidth = 1;
    constraints.gridheight = 1;
    constraints.insets = new Insets(0, 0, 20, 0);
    pantalla.getContentPane().add(tab1Label, constraints);

    constraints.gridx = 1;
    constraints.gridy = 0;
    constraints.gridwidth = 1;
    constraints.gridheight = 1;
    constraints.insets = new Insets(0, 0, 20, 0);
    pantalla.getContentPane().add(tab2Label, constraints);

    constraints.insets = new Insets(0, 0, 0, 0);

    constraints.fill = GridBagConstraints.VERTICAL;
    constraints.gridx = 0;
    constraints.gridy = 1;
    constraints.gridwidth = 1;
    constraints.gridheight = 1;
    pantalla.getContentPane().add(tablero1, constraints);

    constraints.fill = GridBagConstraints.VERTICAL;
    constraints.gridx = 1;
    constraints.gridy = 1;
    constraints.gridwidth = 1;
    constraints.gridheight = 1;
    pantalla.getContentPane().add(tablero2, constraints);

    pantalla.pack();
    pantalla.setSize(800, 400);
    pantalla.setVisible(true);
    pantalla.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
}

And here is the result:

I know there are other ways easier to make it, but to use GridBagLayout is actually a requeriment.

Answer 1

Try to add constraints.weightx = 1; and constraints.weighty = 1; to your JTables constraints.

Also remove those lines:

tablero1.setPreferredSize(new Dimension(400,400));
tablero1.setBounds(0, 0, 400, 400);