5.7 The JCheckBox Class

The JCheckBox^[5] class is shown in various L&Fs in Figure 5-7. JCheckBox is a subclass of JToggleButton and is typically used to allow the user to turn a given feature on or off or to make multiple selections from a set of choices. A JCheckBox is usually rendered by showing a small box into which a "check" is placed when selected (as shown in Figure 5-7). If you specify an icon for the checkbox, this icon replaces the default box. Therefore, if you specify an icon, you should always also supply a selected icon—otherwise, there is no way to tell if a checkbox is selected.

^[5] Note that the java.awt.Checkbox class differs in capitalization from javax.swing.JCheckBox.

Figure 5-7. JCheckBoxes in four L&Fs

5.7.1 Properties

The JCheckBox class inherits most of its properties from its superclasses. The exceptions are shown in Table 5-12. By default, no border is painted on JCheckBoxes, and their horizontalAlignment is to the leading edge (which means to the left in the default locale, in which text reads left to right).^[6] Setting the borderPaintedFlat property to true is a hint to the L&F that the checkbox should be drawn more plainly than usual. (This is used primarily by cell renderers for tables and trees.)

^[6] This locale sensitivity was introduced in SDK 1.4; previously, checkboxes were always aligned to the left.

Table 5-12. JCheckBox properties

Property	Data type	get	is	set	Default value
accessibleContexto	AccessibleContext	·			AccessibleJCheckBox
borderPaintedo	boolean		·	·	false
borderPaintedFlat1.3, b	boolean		·	·	false
horizontalAlignmento	int	·		·	LEADING1.4
UIClassIDo	String	·			"CheckBoxUI"
1.3since 1.3, 1.4since 1.4, b, ooverridden See also properties from JToggleButton (Table 5-10).

5.7.2 Events

See the discussion of JToggleButton (JCheckBox's superclass) events.

5.7.3 Constant

JToggleButton adds one constant for use in PropertyChangeEvents to the list defined by AbstractButton (see Table 5-13).

Table 5-13. JToggleButton constant

Constant	Type	Description
BORDER_PAINTED_FLAT_CHANGED_PROPERTY	String	borderPaintedFlat property has changed
See also the constants defined by AbstractButton in Table 5-7.

5.7.4 Constructors

public JCheckBox( )

Create a checkbox that has no text or icon and is not selected.

public JCheckBox(Action a)

Create a checkbox with property values taken from the specified Action, register the Action to receive ActionEvents fired by the checkbox, and register the checkbox as a ChangeListener of the Action. The checkbox adapts to any future changes made to the Action. The properties set are the ones listed in Table 5-8, except that the SMALL_ICON is not honored since JCheckBox uses its icon property to show its state. (This constructor was introduced with SDK 1.3.)

public JCheckBox(Icon icon)

public JCheckBox(Icon icon, boolean selected)

Create a checkbox that displays the specified icon. If included, the selected parameter determines the initial selection state of the button.

public JCheckBox(String text)

public JCheckBox(String text, boolean selected)

Create a checkbox that displays the specified text. If included, the selected parameter determines the initial selection state of the button.

public JCheckBox(String text, Icon icon)

public JCheckBox(String text, Icon icon, boolean selected)

Create a checkbox that displays the specified text and icon. If included, the selected parameter determines the initial selection state of the button.