GridLayout

How GridLayout works

A GridLayout is a layout manager which places components inside a grid with equal cell sizes. You can set the number of rows, columns, the horizontal gap and the vertical gap using the following methods:

setRows(int rows)
setColumns(int columns)
setHgap(int hgap)
setVgap(int vgap)

or you can set them with the following constructors:

GridLayout(int rows, int columns)
GridLayout(int rows, int columns, int hgap, int vgap)

If the number of rows or columns is unknown, you can set the respective variable to 0. For example:

new GridLayout(0, 3)

This will cause the GridLayout to have 3 columns and as many rows as needed.

The following example demonstrates how a GridLayout lays out components with different values for rows, columns, horizontal gap, vertical gap and screen size.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.GridLayout;

import javax.swing.BorderFactory;
import javax.swing.Box;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSpinner;
import javax.swing.SpinnerNumberModel;
import javax.swing.WindowConstants;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class GridLayoutExample {

    private GridLayout gridLayout;
    private JPanel gridPanel, contentPane;
    private JSpinner rowsSpinner, columnsSpinner, hgapSpinner, vgapSpinner;

    public void createAndShowGUI() {
        gridLayout = new GridLayout(5, 5, 3, 3);

        gridPanel = new JPanel(gridLayout);

        final ChangeListener rowsColumnsListener = new ChangeListener() {
            @Override
            public void stateChanged(ChangeEvent e) {
                gridLayout.setRows((int) rowsSpinner.getValue());
                gridLayout.setColumns((int) columnsSpinner.getValue());
                fillGrid();
            }
        };

        final ChangeListener gapListener = new ChangeListener() {
            @Override
            public void stateChanged(ChangeEvent e) {
                gridLayout.setHgap((int) hgapSpinner.getValue());
                gridLayout.setVgap((int) vgapSpinner.getValue());
                gridLayout.layoutContainer(gridPanel);
                contentPane.revalidate();
                contentPane.repaint();
            }
        };

        rowsSpinner = new JSpinner(new SpinnerNumberModel(gridLayout.getRows(), 1, 10, 1));
        rowsSpinner.addChangeListener(rowsColumnsListener);

        columnsSpinner = new JSpinner(new SpinnerNumberModel(gridLayout.getColumns(), 1, 10, 1));
        columnsSpinner.addChangeListener(rowsColumnsListener);

        hgapSpinner = new JSpinner(new SpinnerNumberModel(gridLayout.getHgap(), 0, 50, 1));
        hgapSpinner.addChangeListener(gapListener);

        vgapSpinner = new JSpinner(new SpinnerNumberModel(gridLayout.getVgap(), 0, 50, 1));
        vgapSpinner.addChangeListener(gapListener);

        JPanel actionPanel = new JPanel();
        actionPanel.add(new JLabel("Rows:"));
        actionPanel.add(rowsSpinner);
        actionPanel.add(Box.createHorizontalStrut(10));
        actionPanel.add(new JLabel("Columns:"));
        actionPanel.add(columnsSpinner);
        actionPanel.add(Box.createHorizontalStrut(10));
        actionPanel.add(new JLabel("Horizontal gap:"));
        actionPanel.add(hgapSpinner);
        actionPanel.add(Box.createHorizontalStrut(10));
        actionPanel.add(new JLabel("Vertical gap:"));
        actionPanel.add(vgapSpinner);

        contentPane = new JPanel(new BorderLayout(0, 10));
        contentPane.add(gridPanel);
        contentPane.add(actionPanel, BorderLayout.SOUTH);
        
        fillGrid();

        JFrame frame = new JFrame("GridLayout Example");
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.setContentPane(contentPane);
        frame.setSize(640, 480);
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private void fillGrid() {
        gridPanel.removeAll();
        for (int row = 0; row < gridLayout.getRows(); row++) {
            for (int col = 0; col < gridLayout.getColumns(); col++) {
                JLabel label = new JLabel("Row: " + row + " Column: " + col);
                label.setHorizontalAlignment(JLabel.CENTER);
                label.setBorder(BorderFactory.createLineBorder(Color.GRAY));
                gridPanel.add(label);
            }
        }
        contentPane.revalidate();
        contentPane.repaint();
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                new GridLayoutExample().createAndShowGUI();
            }
        });
    }

}