Java Foundation Classes in a Nutshell

Some layout managers requir e additional information about the components they

ar e to arrange. This information takes the form of a constraint string or constraint

object passed to the

add() method when the component is added to its container.

java.awt.BorderLayout is the most commonly used of these layout managers: its

constraint object is a string that specifies where the child should be positioned

within the container. Example 2-1 showed a typical use of

BorderLayout.

Every AWT and Swing container has a default layout manager. If you explicitly set

the layout manager to

null, however, you can arrange your components using

hardcoded sizes and positions. Set the size and position with methods such as

setSize() and setLocation(). However, hardcoding the layout of your compo-

nents makes your GUI less portable, harder to customize, and harder to translate

into other languages.

Event Handling

Using a layout manager to arrange components within a container may result in a

GUI that looks good, but in order to make it do anything, you have to handle

events. An event typically signifies an action by the user, such as striking a key or

clicking the mouse over a

JButton component. But it can also refer to any other

action perfor med by the user or the program. An event can be generated when

the value of component’s property changes or when a specified amount of time

elapses, for example.

The event model used in ...