Java Reference
In-Depth Information
Note EXIT_ON_CLOSE was introduced into the JFrame class in Java 1.3, and
subsequently added to WindowsConstants in Java 1.4 (for completeness).
New Lightweight Components and Containers
Swing's lightweight components and containers are implemented by subclasses of the
abstract javax.swing.JComponent class, which extends Container . (I previ-
ouslymentionedthatcomponentsandcontainerscreatedfromcustom Component and
Container subclasses are known as lightweight components and containers.) They
donothavepeersbutreusethepeersoftheir closest heavyweight ancestors. Afterall,
Swing must eventually ensure that the platform's windowing system can display them.
JComponent introduces several new features, including tooltips, borders, and the
option of creating nonrectangular components:
• A tooltip isasmall(typicallyrectangular)windowappearingoveracomponent
with a small amount of help text. JComponent declares a void
setToolTipText(String text) methodforspecifyingthecomponent's
tooltip text.
• A border isanobjectthatsitsbetweenaSwingcomponent'sedgesandthatof
itscontainer. JComponent declaresa void setBorder(Border bor-
der) method for setting the border to border , which is an instance of a
class that implements the javax.swing.border.Border interface. The
javax.swing.BorderFactory class declares several class methods for
returning different kinds of borders. For example, Border cre-
ateEtchedBorder(int type) createsanetchedborderbyinstantiating
the javax.swing.border.EtchedBorder class. The argument passed
to type must be one of EtchedBorder.RAISED or
EtchedBorder.LOWERED .
• Predefined AWT components (such as buttons) are rectangular because their
(bysubclassing JComponent ),youcanmakethemnonrectangularbypassing
false to JComponent 's void setOpaque(boolean isOpaque)
method, which indicates that not every pixel is painted (so background pixels
canshowthrough).Passing true tothismethodindicatesthatthecomponent
paints every pixel. (The default value is false.)
I'll demonstrate tooltips and borders later in this chapter.
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