GUI Components: Part 2 - Java: How to Program Early Objects - page 949

and the gridheight variable specifies the number of rows the Component will span in the
grid. Line 76 sets the GridBagConstraints for a component in the GridBagLayout . Meth-
od setConstraints of class GridBagLayout takes a Component argument and a GridBag-
Constraints argument. Line 77 adds the component to the JFrame .
When you execute this application, try resizing the window to see how the constraints
for each GUI component affect its position and size in the window.

GridBagConstraints Constants RELATIVE and REMAINDER
Instead of gridx and gridy , a variation of GridBagLayout uses GridBagConstraints con-
stants RELATIVE and REMAINDER . RELATIVE specifies that the next-to-last component in a
particular row should be placed to the right of the previous component in the row.
REMAINDER specifies that a component is the last component in a row. Any component that
is not the second-to-last or last component on a row must specify values for GridbagCon-
straints variables gridwidth and gridheight . The application in Figs. 22.23-22.24 ar-
ranges components in GridBagLayout , using these constants.

1 // Fig. 22.23: GridBagFrame2.java

2 // Demonstrating GridBagLayout constants.

3 import java.awt.GridBagLayout;

4

import java.awt.GridBagConstraints;

5

import java.awt.Component;

6

import javax.swing.JFrame;

7 import javax.swing.JComboBox;

8 import javax.swing.JTextField;

9 import javax.swing.JList;

10 import javax.swing.JButton;

11
12 public class GridBagFrame2 extends JFrame

13 {

14 private final GridBagLayout layout; // layout of this frame

15 private final GridBagConstraints constraints; // layout's constraints

16

17 // set up GUI

18 public GridBagFrame2()

19 {

20 super ( "GridBagLayout" );

21 layout = new GridBagLayout();

setLayout(layout); // set frame layout 22

23 constraints = new GridBagConstraints(); // instantiate constraints

24
25 // create GUI components

26 String[] metals = { "Copper" , "Aluminum" , "Silver" };

27 JComboBox comboBox = new JComboBox(metals);

28
29 JTextField textField = new JTextField( "TextField" );

30
31 String[] fonts = { "Serif" , "Monospaced" };

32 JList list = new JList(fonts);

33

Fig. 22.23 | GridBagConstraints constants RELATIVE and REMAINDER . (Part 1 of 2.)