Java Reference
In-Depth Information
Understanding AbstractButton Icons
AbstractButton
has seven specific icon properties. The natural or default icon is the
icon
prop-
erty. It is used for all cases unless a different icon is specified or there is a default behavior
provided by the component. The
selectedIcon
property is the icon used when the button is
selected. The
pressedIcon
is used when the button is pressed. Which of these two icons is used
depends on the component, because a
JButton
is pressed but not selected, whereas a
JCheckBox
is selected but not pressed.
The
disabledIcon
and
disabledSelectedIcon
properties are used when the button has
been disabled with
setEnabled(false)
. By default, if the icon is an
ImageIcon
, a grayscaled
version of the icon will be used.
The remaining two icon properties,
rolloverIcon
and
rolloverSelectedIcon
, allow you to
display different icons when the mouse moves over the button (and
rolloverEnabled
is
true
).
Understanding Internal AbstractButton Positioning
The
horizontalAlignment
,
horizontalTextPosition
,
verticalAlignment
, and
verticalTextPosition
properties share the same settings and behavior as the
JLabel
class.
They're listed in Table 4-13.
Table 4-13.
AbstractButton Position Constants
Position Property
Available Settings
horizontalAlignment
LEFT
,
CENTER
,
RIGHT
horizontalTextPosition
LEFT
,
CENTER
,
RIGHT
verticalAlignment
TOP
,
CENTER
,
BOTTOM
verticalTextPosition
TOP
,
CENTER
,
BOTTOM
Handling AbstractButton Events
Although you do not create
AbstractButton
instances directly, you do create subclasses.
All of them share a common set of event-handling capabilities. You can register
PropertyChangeListener
,
ActionListener
,
ItemListener
, and
ChangeListener
objects with
abstract buttons. The
PropertyChangeListener
object will be discussed here, and the
remaining objects listed will be discussed in later chapters, with the appropriate components.
Like the
JComponent
class, the
AbstractButton
component supports the registering of
PropertyChangeListener
objects to detect when bound properties of an instance of the class
change. Unlike the
JComponent
class, the
AbstractButton
component provides the following set
of class constants to signify the different property changes:
• BORDER_PAINTED_CHANGED_PROPERTY
• CONTENT_AREA_FILLED_CHANGED_PROPERTY
• DISABLED_ICON_CHANGED_PROPERTY
• DISABLED_SELECTED_ICON_CHANGED_PROPERTY
• FOCUS_PAINTED_CHANGED_PROPERTY
