5.2 The DefaultButtonModel Class

Swing provides an implementation of the ButtonModel interface called DefaultButtonModel. This class is used directly by the AbstractButton class and indirectly by the other button classes. JToggleButton defines an inner class extending DefaultButtonModel that it and its descendants use to manage their state data.

5.2.1 Properties

The DefaultButtonModel class gets most of its properties from ButtonModel. The default values set by this class are shown in Table 5-3.

Table 5-3. DefaultButtonModel properties

Property	Data type	get	is	set	Default value
actionCommando	String	·		·	null
armedo	boolean		·	·	false
enabledo	boolean		·	·	true
groupo, *	ButtonGroup	·		·	null
mnemonico	int	·		·	KeyEvent.VK_UNDEFINED
pressedo	boolean		·	·	false
rollovero	boolean		·	·	false
selectedo	boolean		·	·	false
selectedObjects	Object[]	·			null
ooverridden, *getter was introduced in SDK 1.3

The only property here that does not come from the ButtonModel interface is the selectedObjects property. DefaultButtonModel provides a getSelectedObjects( ) method because it is mandated by the ItemSelectable interface, but it always returns null. SDK 1.3 added the getGroup( ) method.

5.2.2 Events

The events fired by DefaultButtonModel are those required by ButtonModel and listed in Table 5-2. An ActionEvent is fired when the button is pressed, an ItemEvent is fired when the button's state is changed, and a ChangeEvent is fired when a change has occurred to the button's properties.

This class implements the following standard methods:

public void addActionListener(ActionListener l)

public void removeActionListener(ActionListener l)

public ActionListener[] getActionListeners( ) (added in SDK 1.3)

public void addItemListener(ItemListener l)

public void removeItemListener(ItemListener l)

public ItemListener[] getItemListeners( ) (added in SDK 1.3)

public void addChangeListener(ChangeListener l)

public void removeChangeListener(ChangeListener l)

public ChangeListener[] getChangeListeners( ) (added in SDK 1.3)

public EventListener[] getListeners(Class listenerType) (added in SDK 1.4)

Note that the ButtonModel properties are not technically "bound properties" as defined by the JavaBeans specification because the lighter-weight ChangeEvent is sent when they change, rather than the standard PropertyChangeEvent.

5.2.3 Constants

DefaultButtonModel uses the constants shown in Table 5-4 to store internal state.

Table 5-4. DefaultButtonModel constants

Constant	Type
ARMED	int
ENABLED	int
PRESSED	int
ROLLOVER	int
SELECTED	int

5.2.4 Constructor

public DefaultButtonModel( )

Instantiates a new model. The model's properties are shown in Table 5-3.