Module java.desktop
Package javax.swing.plaf.basic

Class BasicComboBoxUI

java.lang.Object
javax.swing.plaf.ComponentUI
javax.swing.plaf.ComboBoxUI
javax.swing.plaf.basic.BasicComboBoxUI
Direct Known Subclasses:
MetalComboBoxUI, SynthComboBoxUI
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, override installKeyboardActions to add actions in response to KeyStroke bindings. See the article How to Use Key Bindings

  • Field Details

    • comboBox

      protected JComboBox<Object> comboBox
      The instance of JComboBox.

    • hasFocus

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

    • listBox

      protected JList<Object> listBox
      This list is for drawing the current item in the combo box.

    • currentValuePane

      protected CellRendererPane currentValuePane
      Used to render the currently selected item in the combo box. It doesn't have anything to do with the popup's rendering.

    • editor

      protected Component editor
      The Component that the ComboBoxEditor uses for editing.

    • arrowButton

      protected JButton arrowButton
      The arrow button that invokes the popup.

    • keyListener

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

    • focusListener

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

    • propertyChangeListener

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

    • itemListener

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

    • popupMouseListener

      protected MouseListener popupMouseListener
      The MouseListener listens to events.

    • popupMouseMotionListener

      protected MouseMotionListener popupMouseMotionListener
      The MouseMotionListener listens to events.

    • popupKeyListener

      protected KeyListener popupKeyListener
      The KeyListener listens to events.

    • listDataListener

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

    • isMinimumSizeDirty

      protected boolean isMinimumSizeDirty
      The flag for recalculating the minimum preferred size.

    • cachedMinimumSize

      protected Dimension cachedMinimumSize
      The cached minimum preferred size.

    • 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

  • Constructor Details

    • BasicComboBoxUI

      public BasicComboBoxUI()
      Constructs a BasicComboBoxUI.

  • Method Details

    • createUI

      public static ComponentUI createUI(JComponent c)
      Constructs a new instance of BasicComboBoxUI.
      Parameters:
      c - a component
      Returns:
      a new instance of BasicComboBoxUI

    • 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:

    • 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<Object> 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:

    • 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:

    • 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:

    • removeEditor

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

    • configureEditor

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

    • unconfigureEditor

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

    • configureArrowButton

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

    • unconfigureArrowButton

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

    • 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
      Parameters:
      c - a JComboBox
      Returns:
      true if popup of the JComboBox is visible

    • setPopupVisible

      public void setPopupVisible(JComboBox<?> c, boolean v)
      Hides the popup.
      Specified by:
      setPopupVisible in class ComboBoxUI
      Parameters:
      c - a JComboBox
      v - a boolean determining the visibility of the popup

    • 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
      Parameters:
      c - a JComboBox
      Returns:
      true if the given JComboBox is traversable

    • 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:

    • 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:

    • 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:

    • 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.
      Parameters:
      keyCode - a key code
      Returns:
      true if the supplied keyCode maps to a navigation key

    • 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.
      Returns:
      the area that is reserved for drawing the currently selected item

    • getInsets

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

    • paintCurrentValue

      public void paintCurrentValue(Graphics g, Rectangle bounds, boolean hasFocus)
      Paints the currently selected item.
      Parameters:
      g - an instance of Graphics
      bounds - a bounding rectangle to render to
      hasFocus - is focused

    • paintCurrentValueBackground

      public void paintCurrentValueBackground(Graphics g, Rectangle bounds, boolean hasFocus)
      Paints the background of the currently selected item.
      Parameters:
      g - an instance of Graphics
      bounds - a bounding rectangle to render to
      hasFocus - is focused

    • 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

      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:

    • 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.