Class BasicComboBoxUI

public class BasicComboBoxUI
extends ComboBoxUI

Basic UI implementation for JComboBox.

The combo box is a compound component which means that it is an aggregate 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 How to Use Key Bindings

Fields

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

squareButton

protected boolean squareButton

Indicates whether or not the combo box button should be square. If square, then the width and height are equal, and are both set to the height of the combo minus appropriate insets.

Since:

1.7

padding

protected Insets padding

If specified, these insets act as padding around the cell renderer when laying out and painting the "selected" item in the combo box. These insets add to those specified by the cell renderer.

Since:

1.7

Constructors

BasicComboBoxUI

public BasicComboBoxUI()

Methods

createUI

public static ComponentUI createUI(JComponent c)

installUI

public void installUI(JComponent c)

Description copied from class: ComponentUI

Configures the specified component appropriately 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 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()

Creates and installs 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 from the combo box.

uninstallListeners

protected void uninstallListeners()

Removes 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()

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<? super E>)

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 comprise 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 a 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 appropriately 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 minimum 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

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 size of the display area calculated from the combo box items

See Also:

JComboBox.setPrototypeDisplayValue(E)

getSizeForComponent

protected Dimension getSizeForComponent(Component comp)

Returns the size a component would have if used as a cell renderer.

Parameters:

comp - a Component to check

Returns:

size of the component

Since:

1.7

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.