GUI Components: Part 1 - Java: How to Program Early Objects - page 533

izontally to the sides of the container and are as tall as the components placed in those
regions. The EAST and WEST regions expand vertically between the NORTH and SOUTH
regions and are as wide as the components placed in those regions. The component placed
in the CENTER region expands to fill all remaining space in the layout (which is the reason the
JTextArea in Fig. 12.37 occupies the entire window). If all five regions are occupied, the
entire container's space is covered by GUI components. If the NORTH or SOUTH region is not
occupied, the GUI components in the EAST , CENTER and WEST regions expand vertically to
fill the remaining space. If the EAST or WEST region is not occupied, the GUI component
in the CENTER region expands horizontally to fill the remaining space . If the CENTER region is
not occupied, the area is left empty —the other GUI components do not expand to fill the
remaining space. The application of Figs. 12.41-12.42 demonstrates the BorderLayout
layout manager by using five JButton s.

1

// Fig. 12.41: BorderLayoutFrame.java

2

// BorderLayout containing five buttons.

3

import java.awt.BorderLayout;

4

import java.awt.event.ActionListener;

5

import java.awt.event.ActionEvent;

6

import javax.swing.JFrame;

7

import javax.swing.JButton;

8
9 public class BorderLayoutFrame extends JFrame implements ActionListener

10 {

11 private final JButton[] buttons; // array of buttons to hide portions

12 private static final String[] names = { "Hide North" , "Hide South" ,

13 "Hide East" , "Hide West" , "Hide Center" };

14 private final BorderLayout layout;

15
16 // set up GUI and event handling

17 public BorderLayoutFrame()

18 {

19 super ( "BorderLayout Demo" );

20
21 layout = new BorderLayout( 5 , 5 ); // 5 pixel gaps

22 setLayout(layout);

23 buttons = new JButton[names.length];

24
25 // create JButtons and register listeners for them

26 for ( int count = 0 ; count < names.length; count++)

27 {

28 buttons[count] = new JButton(names[count]);

29 buttons[count].addActionListener( this );

30 }

31
32 add(buttons[ 0 ], BorderLayout.NORTH );

33 add(buttons[ 1 ], BorderLayout.SOUTH );

34 add(buttons[ 2 ], BorderLayout.EAST );

35 add(buttons[ 3 ], BorderLayout.WEST) ;

36 add(buttons[ 4 ], BorderLayout.CENTER );

37 }

Fig. 12.41 | BorderLayout containing five buttons. (Part 1 of 2.)