Java™ Platform
Standard Ed. 6

javax.swing.plaf.basic
Class BasicComboBoxUI

java.lang.Object
  extended by javax.swing.plaf.ComponentUI
      extended by javax.swing.plaf.ComboBoxUI
          extended by javax.swing.plaf.basic.BasicComboBoxUI
Direct Known Subclasses:
MetalComboBoxUI

public class BasicComboBoxUI
extends ComboBoxUI

Basic UI implementation for JComboBox.

The combo box is a compound component which means that it is an agregate of many simpler components. This class creates and manages the listeners on the combo box and the combo box model. These listeners update the user interface in response to changes in the properties and state of the combo box.

All event handling is handled by listener classes created with the createxxxListener() methods and internal classes. You can change the behavior of this class by overriding the createxxxListener() methods and supplying your own event listeners or subclassing from the ones supplied in this class.

For adding specific actions, overide installKeyboardActions to add actions in response to KeyStroke bindings. See the article Keyboard Bindings in Swing at The Swing Connection.


Nested Class Summary
 class BasicComboBoxUI.ComboBoxLayoutManager
          This layout manager handles the 'standard' layout of combo boxes.
 class BasicComboBoxUI.FocusHandler
          This listener hides the popup when the focus is lost.
 class BasicComboBoxUI.ItemHandler
          This listener watches for changes to the selection in the combo box.
 class BasicComboBoxUI.KeyHandler
          This listener checks to see if the key event isn't a navigation key.
 class BasicComboBoxUI.ListDataHandler
          This listener watches for changes in the ComboBoxModel.
 class BasicComboBoxUI.PropertyChangeHandler
          This listener watches for bound properties that have changed in the combo box.
 
Field Summary
protected  JButton arrowButton
           
protected  Dimension cachedMinimumSize
           
protected  JComboBox comboBox
           
protected  CellRendererPane currentValuePane
           
protected  Component editor
           
protected  FocusListener focusListener
          This protected field is implementation specific.
protected  boolean hasFocus
          This protected field is implementation specific.
protected  boolean isMinimumSizeDirty
           
protected  ItemListener itemListener
          This protected field is implementation specific.
protected  KeyListener keyListener
          This protected field is implementation specific.
protected  JList listBox
           
protected  ListDataListener listDataListener
          This protected field is implementation specific.
protected  ComboPopup popup
           
protected  KeyListener popupKeyListener
           
protected  MouseListener popupMouseListener
           
protected  MouseMotionListener popupMouseMotionListener
           
protected  PropertyChangeListener propertyChangeListener
          This protected field is implementation specific.
 
Constructor Summary
BasicComboBoxUI()
           
 
Method Summary
 void addEditor()
          This public method is implementation specific and should be private.
 void configureArrowButton()
          This public method is implementation specific and should be private.
protected  void configureEditor()
          This protected method is implementation specific and should be private.
protected  JButton createArrowButton()
          Creates an button which will be used as the control to show or hide the popup portion of the combo box.
protected  ComboBoxEditor createEditor()
          Creates the default editor that will be used in editable combo boxes.
protected  FocusListener createFocusListener()
          Creates a FocusListener which will be added to the combo box.
protected  ItemListener createItemListener()
          Creates an ItemListener which will be added to the combo box.
protected  KeyListener createKeyListener()
          Creates a KeyListener which will be added to the combo box.
protected  LayoutManager createLayoutManager()
          Creates a layout manager for managing the components which make up the combo box.
protected  ListDataListener createListDataListener()
          Creates a list data listener which will be added to the ComboBoxModel.
protected  ComboPopup createPopup()
          Creates the popup portion of the combo box.
protected  PropertyChangeListener createPropertyChangeListener()
          Creates a PropertyChangeListener which will be added to the combo box.
protected  ListCellRenderer createRenderer()
          Creates the default renderer that will be used in a non-editiable combo box.
static ComponentUI createUI(JComponent c)
           
 Accessible getAccessibleChild(JComponent c, int i)
          Returns the ith Accessible child of the object.
 int getAccessibleChildrenCount(JComponent c)
          Returns the number of accessible children in the object.
 int getBaseline(JComponent c, int width, int height)
          Returns the baseline.
 Component.BaselineResizeBehavior getBaselineResizeBehavior(JComponent c)
          Returns an enum indicating how the baseline of the component changes as the size changes.
protected  Dimension getDefaultSize()
          Return the default size of an empty display area of the combo box using the current renderer and font.
protected  Dimension getDisplaySize()
          Returns the calculated size of the display area.
protected  Insets getInsets()
          Gets the insets from the JComboBox.
 Dimension getMaximumSize(JComponent c)
          Returns the specified component's maximum size appropriate for the look and feel.
 Dimension getMinimumSize(JComponent c)
          The minumum size is the size of the display area plus insets plus the button.
 Dimension getPreferredSize(JComponent c)
          Returns the specified component's preferred size appropriate for the look and feel.
protected  void installComponents()
          Creates and initializes the components which make up the aggregate combo box.
protected  void installDefaults()
          Installs the default colors, default font, default renderer, and default editor into the JComboBox.
protected  void installKeyboardActions()
          Adds keyboard actions to the JComboBox.
protected  void installListeners()
          Create and install the listeners for the combo box and its model.
 void installUI(JComponent c)
          Configures the specified component appropriate for the look and feel.
 boolean isFocusTraversable(JComboBox c)
          Determines if the JComboBox is focus traversable.
protected  boolean isNavigationKey(int keyCode)
          Returns whether or not the supplied keyCode maps to a key that is used for navigation.
 boolean isPopupVisible(JComboBox c)
          Tells if the popup is visible or not.
 void paint(Graphics g, JComponent c)
          Paints the specified component appropriate for the look and feel.
 void paintCurrentValue(Graphics g, Rectangle bounds, boolean hasFocus)
          Paints the currently selected item.
 void paintCurrentValueBackground(Graphics g, Rectangle bounds, boolean hasFocus)
          Paints the background of the currently selected item.
protected  Rectangle rectangleForCurrentValue()
          Returns the area that is reserved for drawing the currently selected item.
 void removeEditor()
          This public method is implementation specific and should be private.
protected  void selectNextPossibleValue()
          Selects the next item in the list.
protected  void selectPreviousPossibleValue()
          Selects the previous item in the list.
 void setPopupVisible(JComboBox c, boolean v)
          Hides the popup.
protected  void toggleOpenClose()
          Hides the popup if it is showing and shows the popup if it is hidden.
 void unconfigureArrowButton()
          This public method is implementation specific and should be private.
protected  void unconfigureEditor()
          This protected method is implementation specific and should be private.
protected  void uninstallComponents()
          The aggregate components which compise the combo box are unregistered and uninitialized.
protected  void uninstallDefaults()
          Uninstalls the default colors, default font, default renderer, and default editor into the JComboBox.
protected  void uninstallKeyboardActions()
          Removes the focus InputMap and ActionMap.
protected  void uninstallListeners()
          Remove the installed listeners from the combo box and its model.
 void uninstallUI(JComponent c)
          Reverses configuration which was done on the specified component during installUI.
 
Methods inherited from class javax.swing.plaf.ComponentUI
contains, update
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

comboBox

protected JComboBox comboBox

hasFocus

protected boolean hasFocus
This protected field is implementation specific. Do not access directly or override.


listBox

protected JList listBox

currentValuePane

protected CellRendererPane currentValuePane

popup

protected ComboPopup popup

editor

protected Component editor

arrowButton

protected JButton arrowButton

keyListener

protected KeyListener keyListener
This protected field is implementation specific. Do not access directly or override. Override the listener construction method instead.

See Also:
createKeyListener()

focusListener

protected FocusListener focusListener
This protected field is implementation specific. Do not access directly or override. Override the listener construction method instead.

See Also:
createFocusListener()

propertyChangeListener

protected PropertyChangeListener propertyChangeListener
This protected field is implementation specific. Do not access directly or override. Override the listener construction method instead.

See Also:
createPropertyChangeListener()

itemListener

protected ItemListener itemListener
This protected field is implementation specific. Do not access directly or override. Override the listener construction method instead.

See Also:
createItemListener()

popupMouseListener

protected MouseListener popupMouseListener

popupMouseMotionListener

protected MouseMotionListener popupMouseMotionListener

popupKeyListener

protected KeyListener popupKeyListener

listDataListener

protected ListDataListener listDataListener
This protected field is implementation specific. Do not access directly or override. Override the listener construction method instead.

See Also:
createListDataListener()

isMinimumSizeDirty

protected boolean isMinimumSizeDirty

cachedMinimumSize

protected Dimension cachedMinimumSize
Constructor Detail

BasicComboBoxUI

public BasicComboBoxUI()
Method Detail

createUI

public static ComponentUI createUI(JComponent c)

installUI

public void installUI(JComponent c)
Description copied from class: ComponentUI
Configures the specified component appropriate for the look and feel. This method is invoked when the ComponentUI instance is being installed as the UI delegate on the specified component. This method should completely configure the component for the look and feel, including the following:
  1. Install any default property values for color, fonts, borders, icons, opacity, etc. on the component. Whenever possible, property values initialized by the client program should not be overridden.
  2. Install a LayoutManager on the component if necessary.
  3. Create/add any required sub-components to the component.
  4. Create/install event listeners on the component.
  5. Create/install a PropertyChangeListener on the component in order to detect and respond to component property changes appropriately.
  6. Install keyboard UI (mnemonics, traversal, etc.) on the component.
  7. Initialize any appropriate instance data.

Overrides:
installUI in class ComponentUI
Parameters:
c - the component where this UI delegate is being installed
See Also:
ComponentUI.uninstallUI(javax.swing.JComponent), JComponent.setUI(javax.swing.plaf.ComponentUI), JComponent.updateUI()

uninstallUI

public void uninstallUI(JComponent c)
Description copied from class: ComponentUI
Reverses configuration which was done on the specified component during installUI. This method is invoked when this UIComponent instance is being removed as the UI delegate for the specified component. This method should undo the configuration performed in installUI, being careful to leave the JComponent instance in a clean state (no extraneous listeners, look-and-feel-specific property objects, etc.). This should include the following:
  1. Remove any UI-set borders from the component.
  2. Remove any UI-set layout managers on the component.
  3. Remove any UI-added sub-components from the component.
  4. Remove any UI-added event/property listeners from the component.
  5. Remove any UI-installed keyboard UI from the component.
  6. Nullify any allocated instance data objects to allow for GC.

Overrides:
uninstallUI in class ComponentUI
Parameters:
c - the component from which this UI delegate is being removed; this argument is often ignored, but might be used if the UI object is stateless and shared by multiple components
See Also:
ComponentUI.installUI(javax.swing.JComponent), JComponent.updateUI()

installDefaults

protected void installDefaults()
Installs the default colors, default font, default renderer, and default editor into the JComboBox.


installListeners

protected void installListeners()
Create and install the listeners for the combo box and its model. This method is called when the UI is installed.


uninstallDefaults

protected void uninstallDefaults()
Uninstalls the default colors, default font, default renderer, and default editor into the JComboBox.


uninstallListeners

protected void uninstallListeners()
Remove the installed listeners from the combo box and its model. The number and types of listeners removed and in this method should be the same that was added in installListeners


createPopup

protected ComboPopup createPopup()
Creates the popup portion of the combo box.

Returns:
an instance of ComboPopup
See Also:
ComboPopup

createKeyListener

protected KeyListener createKeyListener()
Creates a KeyListener which will be added to the combo box. If this method returns null then it will not be added to the combo box.

Returns:
an instance KeyListener or null

createFocusListener

protected FocusListener createFocusListener()
Creates a FocusListener which will be added to the combo box. If this method returns null then it will not be added to the combo box.

Returns:
an instance of a FocusListener or null

createListDataListener

protected ListDataListener createListDataListener()
Creates a list data listener which will be added to the ComboBoxModel. If this method returns null then it will not be added to the combo box model.

Returns:
an instance of a ListDataListener or null

createItemListener

protected ItemListener createItemListener()
Creates an ItemListener which will be added to the combo box. If this method returns null then it will not be added to the combo box.

Subclasses may override this method to return instances of their own ItemEvent handlers.

Returns:
an instance of an ItemListener or null

createPropertyChangeListener

protected PropertyChangeListener createPropertyChangeListener()
Creates a PropertyChangeListener which will be added to the combo box. If this method returns null then it will not be added to the combo box.

Returns:
an instance of a PropertyChangeListener or null

createLayoutManager

protected LayoutManager createLayoutManager()
Creates a layout manager for managing the components which make up the combo box.

Returns:
an instance of a layout manager

createRenderer

protected ListCellRenderer createRenderer()
Creates the default renderer that will be used in a non-editiable combo box. A default renderer will used only if a renderer has not been explicitly set with setRenderer.

Returns:
a ListCellRender used for the combo box
See Also:
JComboBox.setRenderer(javax.swing.ListCellRenderer)

createEditor

protected ComboBoxEditor createEditor()
Creates the default editor that will be used in editable combo boxes. A default editor will be used only if an editor has not been explicitly set with setEditor.

Returns:
a ComboBoxEditor used for the combo box
See Also:
JComboBox.setEditor(javax.swing.ComboBoxEditor)

installComponents

protected void installComponents()
Creates and initializes the components which make up the aggregate combo box. This method is called as part of the UI installation process.


uninstallComponents

protected void uninstallComponents()
The aggregate components which compise the combo box are unregistered and uninitialized. This method is called as part of the UI uninstallation process.


addEditor

public void addEditor()
This public method is implementation specific and should be private. do not call or override. To implement a specific editor create a custom ComboBoxEditor

See Also:
createEditor(), JComboBox.setEditor(javax.swing.ComboBoxEditor), ComboBoxEditor

removeEditor

public void removeEditor()
This public method is implementation specific and should be private. do not call or override.

See Also:
addEditor()

configureEditor

protected void configureEditor()
This protected method is implementation specific and should be private. do not call or override.

See Also:
addEditor()

unconfigureEditor

protected void unconfigureEditor()
This protected method is implementation specific and should be private. Do not call or override.

See Also:
addEditor()

configureArrowButton

public void configureArrowButton()
This public method is implementation specific and should be private. Do not call or override.

See Also:
createArrowButton()

unconfigureArrowButton

public void unconfigureArrowButton()
This public method is implementation specific and should be private. Do not call or override.

See Also:
createArrowButton()

createArrowButton

protected JButton createArrowButton()
Creates an button which will be used as the control to show or hide the popup portion of the combo box.

Returns:
a button which represents the popup control

isPopupVisible

public boolean isPopupVisible(JComboBox c)
Tells if the popup is visible or not.

Specified by:
isPopupVisible in class ComboBoxUI

setPopupVisible

public void setPopupVisible(JComboBox c,
                            boolean v)
Hides the popup.

Specified by:
setPopupVisible in class ComboBoxUI

isFocusTraversable

public boolean isFocusTraversable(JComboBox c)
Determines if the JComboBox is focus traversable. If the JComboBox is editable this returns false, otherwise it returns true.

Specified by:
isFocusTraversable in class ComboBoxUI

paint

public void paint(Graphics g,
                  JComponent c)
Description copied from class: ComponentUI
Paints the specified component appropriate for the look and feel. This method is invoked from the ComponentUI.update method when the specified component is being painted. Subclasses should override this method and use the specified Graphics object to render the content of the component.

Overrides:
paint in class ComponentUI
Parameters:
g - the Graphics context in which to paint
c - the component being painted; this argument is often ignored, but might be used if the UI object is stateless and shared by multiple components
See Also:
ComponentUI.update(java.awt.Graphics, javax.swing.JComponent)

getPreferredSize

public Dimension getPreferredSize(JComponent c)
Description copied from class: ComponentUI
Returns the specified component's preferred size appropriate for the look and feel. If null is returned, the preferred size will be calculated by the component's layout manager instead (this is the preferred approach for any component with a specific layout manager installed). The default implementation of this method returns null.

Overrides:
getPreferredSize in class ComponentUI
Parameters:
c - the component whose preferred size is being queried; this argument is often ignored, but might be used if the UI object is stateless and shared by multiple components
See Also:
JComponent.getPreferredSize(), LayoutManager.preferredLayoutSize(java.awt.Container)

getMinimumSize

public Dimension getMinimumSize(JComponent c)
The minumum size is the size of the display area plus insets plus the button.

Overrides:
getMinimumSize in class ComponentUI
Parameters:
c - the component whose minimum size is being queried; this argument is often ignored, but might be used if the UI object is stateless and shared by multiple components
Returns:
a Dimension object or null
See Also:
JComponent.getMinimumSize(), LayoutManager.minimumLayoutSize(java.awt.Container), ComponentUI.getPreferredSize(javax.swing.JComponent)

getMaximumSize

public Dimension getMaximumSize(JComponent c)
Description copied from class: ComponentUI
Returns the specified component's maximum size appropriate for the look and feel. If null is returned, the maximum size will be calculated by the component's layout manager instead (this is the preferred approach for any component with a specific layout manager installed). The default implementation of this method invokes getPreferredSize and returns that value.

Overrides:
getMaximumSize in class ComponentUI
Parameters:
c - the component whose maximum size is being queried; this argument is often ignored, but might be used if the UI object is stateless and shared by multiple components
Returns:
a Dimension object or null
See Also:
JComponent.getMaximumSize(), LayoutManager2.maximumLayoutSize(java.awt.Container)

getBaseline

public int getBaseline(JComponent c,
                       int width,
                       int height)
Returns the baseline.

Overrides:
getBaseline in class ComponentUI
Parameters:
c - JComponent baseline is being requested for
width - the width to get the baseline for
height - the height to get the baseline for
Returns:
baseline or a value < 0 indicating there is no reasonable baseline
Throws:
NullPointerException - if c is null
IllegalArgumentException - if width or height is < 0
Since:
1.6
See Also:
JComponent.getBaseline(int, int)

getBaselineResizeBehavior

public Component.BaselineResizeBehavior getBaselineResizeBehavior(JComponent c)
Returns an enum indicating how the baseline of the component changes as the size changes.

Overrides:
getBaselineResizeBehavior in class ComponentUI
Parameters:
c - JComponent to return baseline resize behavior for
Returns:
an enum indicating how the baseline changes as the component size changes
Throws:
NullPointerException - if c is null
Since:
1.6
See Also:
JComponent.getBaseline(int, int)

getAccessibleChildrenCount

public int getAccessibleChildrenCount(JComponent c)
Description copied from class: ComponentUI
Returns the number of accessible children in the object. If all of the children of this object implement Accessible, this method should return the number of children of this object. UIs might wish to override this if they present areas on the screen that can be viewed as components, but actual components are not used for presenting those areas. Note: As of v1.3, it is recommended that developers call Component.AccessibleAWTComponent.getAccessibleChildrenCount() instead of this method.

Overrides:
getAccessibleChildrenCount in class ComponentUI
Returns:
the number of accessible children in the object
See Also:
ComponentUI.getAccessibleChild(javax.swing.JComponent, int)

getAccessibleChild

public Accessible getAccessibleChild(JComponent c,
                                     int i)
Description copied from class: ComponentUI
Returns the ith Accessible child of the object. UIs might need to override this if they present areas on the screen that can be viewed as components, but actual components are not used for presenting those areas.

Note: As of v1.3, it is recommended that developers call Component.AccessibleAWTComponent.getAccessibleChild() instead of this method.

Overrides:
getAccessibleChild in class ComponentUI
i - zero-based index of child
Returns:
the ith Accessible child of the object
See Also:
ComponentUI.getAccessibleChildrenCount(javax.swing.JComponent)

isNavigationKey

protected boolean isNavigationKey(int keyCode)
Returns whether or not the supplied keyCode maps to a key that is used for navigation. This is used for optimizing key input by only passing non- navigation keys to the type-ahead mechanism. Subclasses should override this if they change the navigation keys.


selectNextPossibleValue

protected void selectNextPossibleValue()
Selects the next item in the list. It won't change the selection if the currently selected item is already the last item.


selectPreviousPossibleValue

protected void selectPreviousPossibleValue()
Selects the previous item in the list. It won't change the selection if the currently selected item is already the first item.


toggleOpenClose

protected void toggleOpenClose()
Hides the popup if it is showing and shows the popup if it is hidden.


rectangleForCurrentValue

protected Rectangle rectangleForCurrentValue()
Returns the area that is reserved for drawing the currently selected item.


getInsets

protected Insets getInsets()
Gets the insets from the JComboBox.


paintCurrentValue

public void paintCurrentValue(Graphics g,
                              Rectangle bounds,
                              boolean hasFocus)
Paints the currently selected item.


paintCurrentValueBackground

public void paintCurrentValueBackground(Graphics g,
                                        Rectangle bounds,
                                        boolean hasFocus)
Paints the background of the currently selected item.


getDefaultSize

protected Dimension getDefaultSize()
Return the default size of an empty display area of the combo box using the current renderer and font.

Returns:
the size of an empty display area
See Also:
getDisplaySize()

getDisplaySize

protected Dimension getDisplaySize()
Returns the calculated size of the display area. The display area is the portion of the combo box in which the selected item is displayed. This method will use the prototype display value if it has been set.

For combo boxes with a non trivial number of items, it is recommended to use a prototype display value to significantly speed up the display size calculation.

Returns:
the size of the display area calculated from the combo box items
See Also:
JComboBox.setPrototypeDisplayValue(java.lang.Object)

installKeyboardActions

protected void installKeyboardActions()
Adds keyboard actions to the JComboBox. Actions on enter and esc are already supplied. Add more actions as you need them.


uninstallKeyboardActions

protected void uninstallKeyboardActions()
Removes the focus InputMap and ActionMap.


Java™ Platform
Standard Ed. 6

Submit a bug or feature
For further API reference and developer documentation, see Java SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

Copyright © 1993, 2011, Oracle and/or its affiliates. All rights reserved.

Scripting on this page tracks web page traffic, but does not change the content in any way.