Class 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 Link icon

    • comboBox Link icon

      protected JComboBox<Object> comboBox
      The instance of JComboBox.
    • hasFocus Link icon

      protected boolean hasFocus
      This protected field is implementation specific. Do not access directly or override.
    • listBox Link icon

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

      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 Link icon

      protected Component editor
      The Component that the ComboBoxEditor uses for editing.
    • arrowButton Link icon

      protected JButton arrowButton
      The arrow button that invokes the popup.
    • keyListener Link icon

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

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

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

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

      protected MouseListener popupMouseListener
      The MouseListener listens to events.
    • popupMouseMotionListener Link icon

      protected MouseMotionListener popupMouseMotionListener
      The MouseMotionListener listens to events.
    • popupKeyListener Link icon

      protected KeyListener popupKeyListener
      The KeyListener listens to events.
    • listDataListener Link icon

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

      protected boolean isMinimumSizeDirty
      The flag for recalculating the minimum preferred size.
    • cachedMinimumSize Link icon

      protected Dimension cachedMinimumSize
      The cached minimum preferred size.
    • squareButton Link icon

      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 Link icon

      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 Link icon

    • BasicComboBoxUI Link icon

      public BasicComboBoxUI()
      Constructs a BasicComboBoxUI.
  • Method Details Link icon

    • createUI Link icon

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

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

      protected void installListeners()
      Creates and installs listeners for the combo box and its model. This method is called when the UI is installed.
    • uninstallDefaults Link icon

      protected void uninstallDefaults()
      Uninstalls the default colors, default font, default renderer, and default editor from the combo box.
    • uninstallListeners Link icon

      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 Link icon

      protected ComboPopup createPopup()
      Creates the popup portion of the combo box.
      Returns:
      an instance of ComboPopup
      See Also:
    • createKeyListener Link icon

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

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

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

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

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

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

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

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

      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 Link icon

      protected Insets getInsets()
      Gets the insets from the JComboBox.
      Returns:
      the insets
    • paintCurrentValue Link icon

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

      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 Link icon

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