Designing Graphical Interfaces - Beginning Java Programming: The Object-Oriented Approach - page 482

gridBaglayout
The GridBagLayout layout manager is one of the most flexible and complex layout managers Java
provides, while still being easy enough to use in a manual manner ( GroupLayout and SpringLayout
are even more flexible, but almost impossible to use by hand).

A GridBagLayout allows components to be placed in a grid of rows and columns, just like the
GridLayout manager, but unlike GridLayout , cells in a GridBagLayout can have different widths
and heights. In addition, it is possible for components to span across cells.

To arrange components, the GridBagLayout layout manager bases itself on the preferred sizes
set for each component, as well as a series of so‐called constraints, formulated by means of a
GridBagConstraints object. Before you read more about these constraints, the following Try It
Out introduces the GridBagLayout layout manager.

Creating the pocket Calculator with GridBagLayout

try it out

In this Try It Out, you change your pocket calculator from the previous Try It Out to use
GridBagLayout to demonstrate the added flexibility of this layout manager.
1. As always, feel free to create a new project in Eclipse when you want to. Create a class called

GridBagLayoutFrame with the following content:
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.util.HashMap;
import java.util.Map;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextField;

public class GridBagLayoutFrame {

public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setTitle("GridLayout frame");

frame.getContentPane().setLayout(new GridBagLayout());

Map<String, JButton> buttons = makeButtons(
"7", "8", "9", "0", "4", "5", "6", "C",
"1", "2", "3", "=", "+", "-", "*", "/"
);

JTextField resultBox = new JTextField("*** BATTERY EMPTY ***");
resultBox.setEditable(false);

GridBagConstraints constraints = new GridBagConstraints();

// Add number buttons