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Class java.awt.swing.JComboBox

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

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 Swing1.0 applications. It will not be possible to load serialized Swing1.0 objects with future releases of Swing. The JDK1.2 release of Swing will be the compatibility baseline for the serialized form of Swing objects.


Inner Class Summary
 JComboBox.AccessibleJComboBox
The class used to obtain the accessible role for this object.
 JComboBox.KeySelectionManager
The interface that defines a KeySelectionManager.
 
Inner classes inherited from class java.awt.swing.JComponent
 JComponent.AccessibleJComponent
 

Field Summary
String  actionCommand
 
ComboBoxModel  dataModel
 
ComboBoxEditor  editor
 
boolean  isEditable
 
JComboBox.KeySelectionManager  keySelectionManager
 
boolean  lightWeightPopupEnabled
 
int  maximumRowCount
 
ListCellRenderer  renderer
 
Object  selectedItemReminder
 
 
Fields inherited from class java.awt.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(ComboBoxModel aModel)
Creates a JComboBox that takes its items from an existing ComboBoxDataModel.
 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.
 JComboBox()
Creates a JComboBox with a default data model.
 

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.
JComboBox.KeySelectionManager  createDefaultKeySelectionManager()
Returns an instance of the default key-selection manager.
void  fireActionEvent()
Notify all listeners that have registered interest for notification on this event type.
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.
java.awt.swing.plaf.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.
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  isOpaque()
Returns true to indicate that this component paints every pixel in its range.
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
void  removeItemListener(ItemListener aListener)
Removes an ItemListener
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  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(java.awt.swing.plaf.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 java.awt.swing.JComponent
 addAncestorListener, addNotify, addPropertyChangeListener, addVetoableChangeListener, computeVisibleRect, contains, createToolTip, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, fireVetoableChange, getAccessibleContext, getActionForKeyStroke, getAlignmentX, getAlignmentY, getAutoscrolls, getBorder, getBounds, getClientProperty, getComponentGraphics, getConditionForKeyStroke, getDebugGraphicsOptions, getGraphics, getHeight, getInsets, getLocation, getMaximumSize, getMinimumSize, getNextFocusableComponent, getPreferredSize, getRegisteredKeyStrokes, getRootPane, getSize, getToolTipLocation, getToolTipText, getToolTipText, getTopLevelAncestor, getUIClassID, getVisibleRect, getWidth, getX, getY, grabFocus, hasFocus, isDoubleBuffered, isFocusCycleRoot, isFocusTraversable, isLightweightComponent, isManagingFocus, isOpaque, isOptimizedDrawingEnabled, isPaintingTile, isRequestFocusEnabled, isValidateRoot, paint, paintBorder, paintChildren, paintComponent, paintImmediately, paintImmediately, processComponentKeyEvent, processFocusEvent, processKeyEvent, processMouseMotionEvent, putClientProperty, registerKeyboardAction, registerKeyboardAction, removeAncestorListener, removeNotify, removePropertyChangeListener, removeVetoableChangeListener, repaint, repaint, requestDefaultFocus, requestFocus, resetKeyboardActions, reshape, revalidate, scrollRectToVisible, setAlignmentX, setAlignmentY, setAutoscrolls, setBorder, setBounds, setDebugGraphicsOptions, setDoubleBuffered, setMaximumSize, setMinimumSize, setNextFocusableComponent, setOpaque, setPreferredSize, setRequestFocusEnabled, setToolTipText, setUI, setVisible, unregisterKeyboardAction, update, updateUI
 
Methods inherited from class java.awt.Container
 add, add, add, add, add, addContainerListener, addImpl, addNotify, countComponents, deliverEvent, doLayout, findComponentAt, findComponentAt, getAlignmentX, getAlignmentY, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getInsets, getLayout, getMaximumSize, getMinimumSize, getPreferredSize, insets, invalidate, isAncestorOf, layout, list, list, locate, minimumSize, paint, paintComponents, paramString, preferredSize, print, printComponents, processContainerEvent, processEvent, remove, remove, removeAll, removeContainerListener, removeNotify, setLayout, update, validate, validateTree
 
Methods inherited from class java.awt.Component
 action, add, addComponentListener, addFocusListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addNotify, addPropertyChangeListener, addPropertyChangeListener, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, deliverEvent, disable, disableEvents, dispatchEvent, doLayout, enable, enable, enableEvents, enableInputMethods, firePropertyChange, getAlignmentX, getAlignmentY, getBackground, getBounds, getColorModel, getComponentAt, getComponentAt, getCursor, getDropTarget, getFont, getFontMetrics, getForeground, getGraphics, getHeight, getInputContext, getInputMethodRequests, getLocale, getLocation, getLocationOnScreen, getMaximumSize, getMinimumSize, getName, getParent, getPeer, getPreferredSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, invalidate, isDisplayable, isEnabled, isFocusTraversable, isLightweight, isOpaque, isShowing, isValid, isVisible, keyDown, keyUp, layout, list, list, list, list, list, locate, location, lostFocus, minimumSize, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paint, paintAll, paramString, postEvent, preferredSize, prepareImage, prepareImage, print, printAll, processComponentEvent, processEvent, processFocusEvent, processInputMethodEvent, processKeyEvent, processMouseEvent, processMouseMotionEvent, remove, removeComponentListener, removeFocusListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeNotify, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, reshape, resize, resize, setBackground, setBounds, setBounds, setCursor, setDropTarget, setEnabled, setFont, setForeground, setLocale, setLocation, setLocation, setName, setSize, setSize, setVisible, show, show, size, toString, transferFocus, update, validate
 
Methods inherited from class java.lang.Object
 clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, 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 ComboBoxDataModel.
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

setUI

public void setUI(java.awt.swing.plaf.ComboBoxUI ui)
Sets the L&F object that renders this component.
Parameters:
ui - the ComboBoxUI L&F object
See Also:
getUI

updateUI

public void updateUI()
Notification from the UIFactory that the L&F has changed.
Overrides:
updateUI in class JComponent
See Also:
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:
getUIClassID, getUI

getUI

public java.awt.swing.plaf.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

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

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 the receiving JComboBox has no selected item or if the selected item is not in the list of items.
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.
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
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

hidePopup

public void hidePopup()
Causes the combo box to close its popup window

addItemListener

public void addItemListener(ItemListener aListener)
Adds an ItemListener. aListener will receive an event when the selected item changes.
Implements:
addItemListener in interface ItemSelectable
Parameters:
aListener - the ItemListener that is to be notified

removeItemListener

public void removeItemListener(ItemListener aListener)
Removes an ItemListener
Implements:
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.
Implements:
getSelectedObjects in interface ItemSelectable

actionPerformed

public void actionPerformed(ActionEvent e)
This method is public as an implementation side effect. do not call or override.
Implements:
actionPerformed in interface ActionListener

contentsChanged

public void contentsChanged(ListDataEvent e)
This method is public as an implementation side effect. do not call or override.
Implements:
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.
Implements:
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.
Implements:
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 Component

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

isOpaque

public boolean isOpaque()
Returns true to indicate that this component paints every pixel in its range. (In other words, it does not have a transparent background or foreground.)
Overrides:
isOpaque in class JComponent
See Also:
isOpaque

getAccessibleContext

public AccessibleContext getAccessibleContext()
Get the AccessibleContext associated with this JComponent
Implements:
getAccessibleContext in interface Accessible
Returns:
the AccessibleContext of this JComponent
Overrides:
getAccessibleContext in class JComponent

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