Java Reference
In-Depth Information
Look-and-Feel Observation 12.5
Swing GUI components allow you to specify a uniform look-and-feel for your application
across
all
platforms
or
to use each platform's custom look-and-feel. An application can
even
change
the look-and-feel during execution to enable users to choose their own pre-
ferred look-and-feel.
Lightweight vs. Heavyweight GUI Components
Most Swing components are
lightweight components
—they're written, manipulated and
displayed completely in Java. AWT components are
heavyweight components
, because
they rely on the local platform's
windowing system
to determine their functionality and
their look-and-feel. Several Swing components are
heavyweight
components.
Superclasses of Swing's Lightweight GUI Components
The UML class diagram of Fig. 12.5 shows an
inheritance hierarchy
of classes from which
lightweight Swing components inherit their common attributes and behaviors.
Object
Component
Container
JComponent
Fig. 12.5
|
Common superclasses of the lightweight Swing components.
Class
Component
(package
java.awt
) is a superclass that declares the common features
of GUI components in packages
java.awt
and
javax.swing
. Any object that
is a
Con-
tainer
(package
java.awt
) can be used to organize
Component
s by
attaching
the
Compo-
nent
s to the
Container
.
Container
s can be placed in other
Container
s to organize a GUI.
Class
JComponent
(package
javax.swing
) is a subclass of
Container
.
JComponent
is
the superclass of all
lightweight
Swing components and declares their common attributes
and behaviors. Because
JComponent
is a subclass of
Container
, all lightweight Swing com-
ponents are also
Container
s. Some common features supported by
JComponent
include:
1.
A
pluggable look-and-feel
for
customizing
the appearance of components (e.g.,
for use on particular platforms). You'll see an example of this in Section 22.6.
2.
Shortcut keys (called
mnemonics
) for direct access to GUI components through
the keyboard. You'll see an example of this in Section 22.4.
3.
Brief descriptions of a GUI component's purpose (called
tool tips
) that are dis-
played when the
mouse cursor is positioned over the component
for a short time.
You'll see an example of this in the next section.
4.
Support for
accessibility
, such as braille screen readers for the visually impaired.
5.
Support for user-interface
localization
—that is, customizing the user interface to
display in different languages and use local cultural conventions.
