GUI BASICS - Introduction to Java Programming - page 452

12.5.1 FlowLayout
FlowLayout is the simplest layout manager. The components are arranged in the container
from left to right in the order in which they were added. When one row is filled, a new row is
started. You can specify the way the components are aligned by using one of three constants:
FlowLayout.RIGHT , FlowLayout.CENTER , or FlowLayout.LEFT . You can also specify
the gap between components in pixels. The class diagram for FlowLayout is shown in
Figure 12.4.

VideoNote

Use FlowLayout

The get and set methods for these data
fields are provided in the class, but
omitted in the UML diagram for brevity.

java.awt.FlowLayout

-alignment: int
-hgap: int
-vgap: int

The alignment of this layout manager (default: CENTER ).
The horizontal gap between the components (default: 5 pixels).
The vertical gap between the components (default: 5 pixels).

+FlowLayout()
+FlowLayout(alignment: int)
+FlowLayout(alignment: int, hgap:
int, vgap: int)

Creates a default FlowLayout manager.
Creates a FlowLayout manager with a specified alignment.
Creates a FlowLayout manager with a specified alignment,
horizontal gap, and vertical gap.

F IGURE 12.4

FlowLayout lays out components row by row.

Listing 12.3 gives a program that demonstrates flow layout. The program adds three labels
and text fields to the frame with a FlowLayout manager, as shown in Figure 12.5.

L ISTING 12.3 ShowFlowLayout.java
1 import javax.swing.JLabel;

2 import javax.swing.JTextField;

3 import javax.swing.JFrame;

4 import java.awt.FlowLayout;

5
6 public class ShowFlowLayout extends JFrame {

extends JFrame

7 public ShowFlowLayout() {
8 // Set FlowLayout, aligned left with horizontal gap 10
9 // and vertical gap 20 between components
10 setLayout(

new FlowLayout(FlowLayout.LEFT, 10 , 20 ) );

set layout

11
12 // Add labels and text fields to the frame
13 add( new JLabel( "First Name" ));
14 add( new JTextField( 8 ));
15 add( new JLabel( "MI" ));
16 add( new JTextField( 1 ));
17 add( new JLabel( "Last Name" ));
18 add( new JTextField( 8 ));
19 }
20
21 /** Main method */
22 public static void main(String[] args) {
23 ShowFlowLayout frame = new ShowFlowLayout();
24 frame.setTitle( "ShowFlowLayout" );
25 frame.setSize( 200 , 200 );

add label
add text field