javax.swing
Class JComboBox

java.lang.Object
  |
  +--java.awt.Component
        |
        +--java.awt.Container
              |
              +--javax.swing.JComponent
                    |
                    +--javax.swing.JComboBox

public class JComboBox

extends JComponent

implements ItemSelectable, ListDataListener, ActionListener, Accessible

Swing's implementation of a ComboBox -- a combination of a text field and drop-down list that lets the user either type in a value or select it from a list that is displayed when the user asks for it. The editing capability can also be disabled so that the JComboBox acts only as a drop down list.

For the keyboard keys used by this component in the standard Look and Feel (L&F) renditions, see the JComboBox key assignments.

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. A future release of Swing will provide support for long term persistence.

See Also:

Serialized Form

Inner Class Summary

protected class	JComboBox.AccessibleJComboBox The class used to obtain the accessible role for this object.
static interface	JComboBox.KeySelectionManager The interface that defines a KeySelectionManager.

Inner classes inherited from class javax.swing.JComponent

JComponent.AccessibleJComponent

Field Summary

protected String	actionCommand
protected ComboBoxModel	dataModel
protected ComboBoxEditor	editor
protected boolean	isEditable
protected JComboBox.KeySelectionManager	keySelectionManager
protected boolean	lightWeightPopupEnabled
protected int	maximumRowCount
protected ListCellRenderer	renderer
protected Object	selectedItemReminder

Fields inherited from class javax.swing.JComponent

accessibleContext, listenerList, TOOL_TIP_TEXT_KEY, ui, UNDEFINED_CONDITION, WHEN_ANCESTOR_OF_FOCUSED_COMPONENT, WHEN_FOCUSED, WHEN_IN_FOCUSED_WINDOW

Fields inherited from class java.awt.Component

BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT

Constructor Summary

JComboBox()
Creates a JComboBox with a default data model.

JComboBox(ComboBoxModel aModel)
Creates a JComboBox that takes its items from an existing ComboBoxModel.

JComboBox(Object[] items)
Creates a JComboBox that contains the elements in the specified array.

JComboBox(Vector items)
Creates a JComboBox that contains the elements in the specified Vector.

Method Summary

void	actionPerformed(ActionEvent e) This method is public as an implementation side effect.
void	addActionListener(ActionListener l) Adds an ActionListener.
void	addItem(Object anObject) Adds an item to the item list.
void	addItemListener(ItemListener aListener) Adds an ItemListener.
void	configureEditor(ComboBoxEditor anEditor, Object anItem) Initializes the editor with the specified item.
void	contentsChanged(ListDataEvent e) This method is public as an implementation side effect.
protected JComboBox.KeySelectionManager	createDefaultKeySelectionManager() Returns an instance of the default key-selection manager.
protected void	fireActionEvent() Notify all listeners that have registered interest for notification on this event type.
protected void	fireItemStateChanged(ItemEvent e) Notify all listeners that have registered interest for notification on this event type.
AccessibleContext	getAccessibleContext() Get the AccessibleContext associated with this JComponent
String	getActionCommand() Returns the action commnand that is included in the event sent to action listeners.
ComboBoxEditor	getEditor() Returns the editor used to paint and edit the selected item in the JComboBox field.
Object	getItemAt(int index) Returns the list item at the specified index.
int	getItemCount() Returns the number of items in the list.
JComboBox.KeySelectionManager	getKeySelectionManager() Returns the list's key-selection manager.
int	getMaximumRowCount() Returns the maximum number of items the combo box can display without a scrollbar
ComboBoxModel	getModel() Returns the data model currently used by the JComboBox.
ListCellRenderer	getRenderer() Returns the renderer used to display the selected item in the JComboBox field.
int	getSelectedIndex() Returns the index of the currently selected item in the list.
Object	getSelectedItem() Returns the currently selected item.
Object[]	getSelectedObjects() Returns an array containing the selected item.
ComboBoxUI	getUI() Returns the L&F object that renders this component.
String	getUIClassID() Returns the name of the L&F class that renders this component.
void	hidePopup() Causes the combo box to close its popup window
void	insertItemAt(Object anObject, int index) Inserts an item into the item list at a given index.
protected void	installAncestorListener()
void	intervalAdded(ListDataEvent e) Invoked items have been added to the internal data model.
void	intervalRemoved(ListDataEvent e) Invoked when values have been removed from the data model.
boolean	isEditable() Returns true if the JComboBox is editable.
boolean	isFocusTraversable() Returns true if the component can receive the focus.
boolean	isLightWeightPopupEnabled() Returns true if lightweight (all-Java) popups are in use, or false if heavyweight (native peer) popups are being used.
boolean	isPopupVisible() Determine the visibility of the popup
protected String	paramString() Returns a string representation of this JComboBox.
void	processKeyEvent(KeyEvent e) Handles KeyEvents, looking for the Tab key.
void	removeActionListener(ActionListener l) Removes an ActionListener
void	removeAllItems() Removes all items from the item list.
void	removeItem(Object anObject) Removes an item from the item list.
void	removeItemAt(int anIndex) Removes the item at anIndex This method works only if the JComboBox uses the default data model.
void	removeItemListener(ItemListener aListener) Removes an ItemListener
protected void	selectedItemChanged() This method is called when the selected item changes.
boolean	selectWithKeyChar(char keyChar) Selects the list item that correponds to the specified keyboard character and returns true, if there is an item corresponding to that character.
void	setActionCommand(String aCommand) Sets the action commnand that should be included in the event sent to action listeners.
void	setEditable(boolean aFlag) Determines whether the JComboBox field is editable.
void	setEditor(ComboBoxEditor anEditor) Sets the editor used to paint and edit the selected item in the JComboBox field.
void	setEnabled(boolean b) Enables the combo box so that items can be selected.
void	setKeySelectionManager(JComboBox.KeySelectionManager aManager) Sets the object that translates a keyboard character into a list selection.
void	setLightWeightPopupEnabled(boolean aFlag) When displaying the popup, JComboBox choose to use a light weight popup if it fits.
void	setMaximumRowCount(int count) Sets the maximum number of rows the JComboBox displays.
void	setModel(ComboBoxModel aModel) Sets the data model that the JComboBox uses to obtain the list of items.
void	setPopupVisible(boolean v) Set the visiblity of the popup
void	setRenderer(ListCellRenderer aRenderer) Sets the renderer that paints the item selected from the list in the JComboBox field.
void	setSelectedIndex(int anIndex) Selects the item at index anIndex.
void	setSelectedItem(Object anObject) Sets the selected item in the JComboBox by specifying the object in the list.
void	setUI(ComboBoxUI ui) Sets the L&F object that renders this component.
void	showPopup() Causes the combo box to display its popup window
void	updateUI() Notification from the UIFactory that the L&F has changed.

Methods inherited from class javax.swing.JComponent

addAncestorListener, addNotify, addPropertyChangeListener, addVetoableChangeListener, computeVisibleRect, contains, createToolTip, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, fireVetoableChange, getActionForKeyStroke, getAlignmentX, getAlignmentY, getAutoscrolls, getBorder, getBounds, getClientProperty, getComponentGraphics, getConditionForKeyStroke, getDebugGraphicsOptions, getGraphics, getHeight, getInsets, getInsets, getLocation, getMaximumSize, getMinimumSize, getNextFocusableComponent, getPreferredSize, getRegisteredKeyStrokes, getRootPane, getSize, getToolTipLocation, getToolTipText, getToolTipText, getTopLevelAncestor, getVisibleRect, getWidth, getX, getY, grabFocus, hasFocus, isDoubleBuffered, isFocusCycleRoot, isLightweightComponent, isManagingFocus, isOpaque, isOptimizedDrawingEnabled, isPaintingTile, isRequestFocusEnabled, isValidateRoot, paint, paintBorder, paintChildren, paintComponent, paintImmediately, paintImmediately, processComponentKeyEvent, processFocusEvent, processMouseMotionEvent, putClientProperty, registerKeyboardAction, registerKeyboardAction, removeAncestorListener, removeNotify, removePropertyChangeListener, removeVetoableChangeListener, repaint, repaint, requestDefaultFocus, requestFocus, resetKeyboardActions, reshape, revalidate, scrollRectToVisible, setAlignmentX, setAlignmentY, setAutoscrolls, setBackground, setBorder, setDebugGraphicsOptions, setDoubleBuffered, setFont, setForeground, setMaximumSize, setMinimumSize, setNextFocusableComponent, setOpaque, setPreferredSize, setRequestFocusEnabled, setToolTipText, setUI, setVisible, unregisterKeyboardAction, update

Methods inherited from class java.awt.Container

add, add, add, add, add, addContainerListener, addImpl, countComponents, deliverEvent, doLayout, findComponentAt, findComponentAt, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getLayout, insets, invalidate, isAncestorOf, layout, list, list, locate, minimumSize, paintComponents, preferredSize, print, printComponents, processContainerEvent, processEvent, remove, remove, removeAll, removeContainerListener, setLayout, validate, validateTree

Methods inherited from class java.awt.Component

action, add, addComponentListener, addFocusListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addPropertyChangeListener, bounds, checkImage, checkImage, coalesceEvents, contains, createImage, createImage, disable, disableEvents, dispatchEvent, enable, enable, enableEvents, enableInputMethods, getBackground, getBounds, getColorModel, getComponentOrientation, getCursor, getDropTarget, getFont, getFontMetrics, getForeground, getInputContext, getInputMethodRequests, getLocale, getLocation, getLocationOnScreen, getName, getParent, getPeer, getSize, getToolkit, getTreeLock, gotFocus, handleEvent, hide, imageUpdate, inside, isDisplayable, isEnabled, isLightweight, isShowing, isValid, isVisible, keyDown, keyUp, list, list, list, location, lostFocus, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, postEvent, prepareImage, prepareImage, printAll, processComponentEvent, processInputMethodEvent, processMouseEvent, remove, removeComponentListener, removeFocusListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removePropertyChangeListener, repaint, repaint, repaint, resize, resize, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setLocale, setLocation, setLocation, setName, setSize, setSize, show, show, size, toString, transferFocus

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

dataModel

protected ComboBoxModel dataModel

renderer

protected ListCellRenderer renderer

editor

protected ComboBoxEditor editor

maximumRowCount

protected int maximumRowCount

isEditable

protected boolean isEditable

selectedItemReminder

protected Object selectedItemReminder

keySelectionManager

protected JComboBox.KeySelectionManager keySelectionManager

actionCommand

protected String actionCommand

lightWeightPopupEnabled

protected boolean lightWeightPopupEnabled

Constructor Detail

JComboBox

public JComboBox(ComboBoxModel aModel)

Creates a JComboBox that takes its items from an existing ComboBoxModel.

Parameters:

aModel - the ComboBoxModel that provides the displayed list of items

JComboBox

public JComboBox(Object[] items)

Creates a JComboBox that contains the elements in the specified array.

JComboBox

public JComboBox(Vector items)

Creates a JComboBox that contains the elements in the specified Vector.

JComboBox

public JComboBox()

Creates a JComboBox with a default data model. The default data model is an empty list of objects. Use addItem to add items.

Method Detail

installAncestorListener

protected void installAncestorListener()

setUI

public void setUI(ComboBoxUI ui)

Sets the L&F object that renders this component.

Parameters:

ui - the ComboBoxUI L&F object

See Also:

UIDefaults.getUI(javax.swing.JComponent)

updateUI

public void updateUI()

Notification from the UIFactory that the L&F has changed.

Overrides:

updateUI in class JComponent

See Also:

JComponent.updateUI()

getUIClassID

public String getUIClassID()

Returns the name of the L&F class that renders this component.

Returns:

"ComboBoxUI"

Overrides:

getUIClassID in class JComponent

See Also:

JComponent.getUIClassID(), UIDefaults.getUI(javax.swing.JComponent)

getUI

public ComboBoxUI getUI()

Returns the L&F object that renders this component.

Returns:

the ComboBoxUI object that renders this component

setModel

public void setModel(ComboBoxModel aModel)

Sets the data model that the JComboBox uses to obtain the list of items.

Parameters:

aModel - the ComboBoxModel that provides the displayed list of items

getModel

public ComboBoxModel getModel()

Returns the data model currently used by the JComboBox.

Returns:

the ComboBoxModel that provides the displayed list of items

setLightWeightPopupEnabled

public void setLightWeightPopupEnabled(boolean aFlag)

When displaying the popup, JComboBox choose to use a light weight popup if it fits. This method allows you to disable this feature. You have to do disable it if your application mixes light weight and heavy weights components.

isLightWeightPopupEnabled

public boolean isLightWeightPopupEnabled()

Returns true if lightweight (all-Java) popups are in use, or false if heavyweight (native peer) popups are being used.

Returns:

true if lightweight popups are in use

setEditable

public void setEditable(boolean aFlag)

Determines whether the JComboBox field is editable. An editable JComboBox allows the user to type into the field or selected an item from the list to initialize the field, after which it can be edited. (The editing affects only the field, the list item remains intact.) A non editable JComboBox displays the selected item inthe field, but the selection cannot be modified.

Parameters:

aFlag - a boolean value, where true indicates that the field is editable

isEditable

public boolean isEditable()

Returns true if the JComboBox is editable.

Returns:

true if the JComboBox is editable, else false

setMaximumRowCount

public void setMaximumRowCount(int count)

Sets the maximum number of rows the JComboBox displays. If the number of objects in the model is greater than count, the combo box uses a scrollbar.

Parameters:

count - an int specifying the maximum number of items to display in the list before using a scrollbar

getMaximumRowCount

public int getMaximumRowCount()

Returns the maximum number of items the combo box can display without a scrollbar

Returns:

an int specifying the maximum number of items that are displayed in the list before using a scrollbar

setRenderer

public void setRenderer(ListCellRenderer aRenderer)

Sets the renderer that paints the item selected from the list in the JComboBox field. The renderer is used if the JComboBox is not editable. If it is editable, the editor is used to render and edit the selected item.

The default renderer displays a string, obtained by calling the selected object's toString method. Other renderers can handle graphic images and composite items.

To display the selected item, aRenderer.getListCellRendererComponent is called, passing the list object and an index of -1.

Parameters:

aRenderer - the ListCellRenderer that displays the selected item.

See Also:

setEditor(javax.swing.ComboBoxEditor)

getRenderer

public ListCellRenderer getRenderer()

Returns the renderer used to display the selected item in the JComboBox field.

Returns:

the ListCellRenderer that displays the selected item.

setEditor

public void setEditor(ComboBoxEditor anEditor)

Sets the editor used to paint and edit the selected item in the JComboBox field. The editor is used only if the receiving JComboBox is editable. If not editable, the combo box uses the renderer to paint the selected item.

Parameters:

anEditor - the ComboBoxEditor that displays the selected item

See Also:

setRenderer(javax.swing.ListCellRenderer)

getEditor

public ComboBoxEditor getEditor()

Returns the editor used to paint and edit the selected item in the JComboBox field.

Returns:

the ComboBoxEditor that displays the selected item

setSelectedItem

public void setSelectedItem(Object anObject)

Sets the selected item in the JComboBox by specifying the object in the list. If anObject is in the list, the list displays with anObject selected. If the object does not exist in the list, the default data model selects the first item in the list.

Parameters:

anObject - the list object to select

getSelectedItem

public Object getSelectedItem()

Returns the currently selected item.

Returns:

the currently selected list object from the data model

setSelectedIndex

public void setSelectedIndex(int anIndex)

Selects the item at index anIndex.

Parameters:

anIndex - an int specifying the list item to select, where 0 specifies the first item in the list

getSelectedIndex

public int getSelectedIndex()

Returns the index of the currently selected item in the list. The result is not always defined if the JComboBox box allows selected items that are not in the list. Returns -1 if there is no selected item or if the user specified an item which is not in the list.

Returns:

an int specifying the currently selected list item, where 0 specifies the first item in the list, or -1 if no item is selected or if the currently selected item is not in the list

addItem

public void addItem(Object anObject)

Adds an item to the item list. This method works only if the JComboBox uses the default data model. JComboBox uses the default data model when created with the empty constructor and no other model has been set.

Parameters:

anObject - the Object to add to the list

insertItemAt

public void insertItemAt(Object anObject,
                         int index)

Inserts an item into the item list at a given index. This method works only if the JComboBox uses the default data model. JComboBox uses the default data model when created with the empty constructor and no other model has been set.

Parameters:

anObject - the Object to add to the list

index - an int specifying the position at which to add the item

removeItem

public void removeItem(Object anObject)

Removes an item from the item list. This method works only if the JComboBox uses the default data model. JComboBox uses the default data model when created with the empty constructor and no other model has been set.

Parameters:

anObject - the object to remove from the item list

removeItemAt

public void removeItemAt(int anIndex)

Removes the item at anIndex This method works only if the JComboBox uses the default data model. JComboBox uses the default data model when created with the empty constructor and no other model has been set.

Parameters:

anIndex - an int specifying the idex of the item to remove, where 0 indicates the first item in the list

removeAllItems

public void removeAllItems()

Removes all items from the item list. This method works only if the JComboBox uses the default data model. JComboBox uses the default data model when created with the empty constructor and no other model has been set.

showPopup

public void showPopup()

Causes the combo box to display its popup window

See Also:

setPopupVisible(boolean)

hidePopup

public void hidePopup()

Causes the combo box to close its popup window

See Also:

setPopupVisible(boolean)

setPopupVisible

public void setPopupVisible(boolean v)

Set the visiblity of the popup

isPopupVisible

public boolean isPopupVisible()

Determine the visibility of the popup

addItemListener

public void addItemListener(ItemListener aListener)

Adds an ItemListener. aListener will receive an event when the selected item changes.

Specified by:

addItemListener in interface ItemSelectable

Parameters:

aListener - the ItemListener that is to be notified

removeItemListener

public void removeItemListener(ItemListener aListener)

Removes an ItemListener

Specified by:

removeItemListener in interface ItemSelectable

Parameters:

aListener - the ItemListener to remove

addActionListener

public void addActionListener(ActionListener l)

Adds an ActionListener. The listener will receive an action event the user finishes making a selection.

Parameters:

l - the ActionListener that is to be notified

removeActionListener

public void removeActionListener(ActionListener l)

Removes an ActionListener

Parameters:

l - the ActionListener to remove

setActionCommand

public void setActionCommand(String aCommand)

Sets the action commnand that should be included in the event sent to action listeners.

Parameters:

aCommand - a string containing the "command" that is sent to action listeners. The same listener can then do different things depending on the command it receives.

getActionCommand

public String getActionCommand()

Returns the action commnand that is included in the event sent to action listeners.

Returns:

the string containing the "command" that is sent to action listeners.

fireItemStateChanged

protected void fireItemStateChanged(ItemEvent e)

Notify all listeners that have registered interest for notification on this event type.

See Also:

EventListenerList

fireActionEvent

protected void fireActionEvent()

Notify all listeners that have registered interest for notification on this event type.

See Also:

EventListenerList

selectedItemChanged

protected void selectedItemChanged()

This method is called when the selected item changes. Its default implementation notifies the item listeners

getSelectedObjects

public Object[] getSelectedObjects()

Returns an array containing the selected item. This method is implemented for compatibility with ItemSelectable.

Specified by:

getSelectedObjects in interface ItemSelectable

actionPerformed

public void actionPerformed(ActionEvent e)

This method is public as an implementation side effect. do not call or override.

Specified by:

actionPerformed in interface ActionListener

contentsChanged

public void contentsChanged(ListDataEvent e)

This method is public as an implementation side effect. do not call or override.

Specified by:

contentsChanged in interface ListDataListener

See Also:

ListDataListener

selectWithKeyChar

public boolean selectWithKeyChar(char keyChar)

Selects the list item that correponds to the specified keyboard character and returns true, if there is an item corresponding to that character. Otherwise, returns false.

Parameters:

keyChar - a char, typically this is a keyboard key typed by the user

intervalAdded

public void intervalAdded(ListDataEvent e)

Invoked items have been added to the internal data model. The "interval" includes the first and last values added.

Specified by:

intervalAdded in interface ListDataListener

See Also:

ListDataListener

intervalRemoved

public void intervalRemoved(ListDataEvent e)

Invoked when values have been removed from the data model. The"interval" includes the first and last values removed.

Specified by:

intervalRemoved in interface ListDataListener

See Also:

ListDataListener

setEnabled

public void setEnabled(boolean b)

Enables the combo box so that items can be selected. When the combo box is disabled, items cannot be selected and values cannot be typed into its field (if it is editable).

Parameters:

b - a boolean value, where true enables the component and false disables it

Overrides:

setEnabled in class JComponent

configureEditor

public void configureEditor(ComboBoxEditor anEditor,
                            Object anItem)

Initializes the editor with the specified item.

Parameters:

anEditor - the ComboBoxEditor that displays the list item in the combo box field and allows it to be edited

anItem - the object to display and edit in the field

processKeyEvent

public void processKeyEvent(KeyEvent e)

Handles KeyEvents, looking for the Tab key. If the Tab key is found, the popup window is closed.

Parameters:

e - the KeyEvent containing the keyboard key that was pressed

Overrides:

processKeyEvent in class JComponent

isFocusTraversable

public boolean isFocusTraversable()

Returns true if the component can receive the focus. In this case, the component returns false if it is editable, so that the Editor object receives the focus, instead of the component.

Returns:

true if the component can receive the focus, else false.

Overrides:

isFocusTraversable in class JComponent

setKeySelectionManager

public void setKeySelectionManager(JComboBox.KeySelectionManager aManager)

Sets the object that translates a keyboard character into a list selection. Typically, the first selection with a matching first character becomes the selected item.

getKeySelectionManager

public JComboBox.KeySelectionManager getKeySelectionManager()

Returns the list's key-selection manager.

Returns:

the KeySelectionManager currently in use

getItemCount

public int getItemCount()

Returns the number of items in the list.

Returns:

an int equal to the number of items in the list

getItemAt

public Object getItemAt(int index)

Returns the list item at the specified index.

Parameters:

index - an int indicating the list position, where the first item starts at zero

Returns:

the Object at that list position

createDefaultKeySelectionManager

protected JComboBox.KeySelectionManager createDefaultKeySelectionManager()

Returns an instance of the default key-selection manager.

Returns:

the KeySelectionManager currently used by the list

See Also:

setKeySelectionManager(javax.swing.JComboBox.KeySelectionManager)

paramString

protected String paramString()

Returns a string representation of this JComboBox. This method is intended to be used only for debugging purposes, and the content and format of the returned string may vary between implementations. The returned string may be empty but may not be null.

Overriding paramString() to provide information about the specific new aspects of the JFC components.

Returns:

a string representation of this JComboBox.

Overrides:

paramString in class JComponent

getAccessibleContext

public AccessibleContext getAccessibleContext()

Get the AccessibleContext associated with this JComponent

Specified by:

getAccessibleContext in interface Accessible

Returns:

the AccessibleContext of this JComponent

Overrides:

getAccessibleContext in class JComponent