Graphical User Interfaces - Building Java Programs: A Back to Basics Approach - page 838

You can construct a JPanel object with no parameters, or you can specify the lay-
out manager to use. Once you've constructed the panel, you can add components to it
using its add method:
// creates a JPanel container with a FlowLayout
JPanel panel = new JPanel(new FlowLayout());
panel.add(new JButton("button 1"));
panel.add(new JButton("button 2"));
A common strategy is to use a BorderLayout for the frame, then add panels to
some or all of its five regions. For example, the following code produces a window
that looks like a telephone keypad, using a panel with a GridLayout in the center
region of the frame and a second panel with a FlowLayout in the south region of
the frame:
1 // A GUI that resembles a telephone keypad.
2
3 import java.awt.*;
4 import javax.swing.*;
5
6 public class Telephone {
7 public static void main(String[] args) {
8 JFrame frame = new JFrame();
9 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
10 frame.setSize( new Dimension(250, 200));
11 frame.setTitle("Telephone");
12
13 frame.setLayout( new BorderLayout());
14
15 // main phone buttons
16 JPanel centerPanel = new JPanel( new GridLayout(4, 3));
17 for ( int i = 1; i <= 9; i++) {
18 centerPanel.add( new JButton("" + i));
19 }
20 centerPanel.add( new JButton("*"));
21 centerPanel.add( new JButton("0"));
22 centerPanel.add( new JButton("#"));
23 frame.add(centerPanel, BorderLayout.CENTER);
24
25 // south status panel
26 JPanel southPanel = new JPanel( new FlowLayout());
27 southPanel.add( new JLabel("Number to dial: "));
28 southPanel.add( new JTextField(10));
29 frame.add(southPanel, BorderLayout.SOUTH);