Warning: We recommend that you not create subclasses of this class. If you absolutely must create a subclass, be sure to invoke the superclass version of each method. 

All the functionality of this class has been included in BasicComboBoxUI ActionMap/InputMap methods. 

The functionality has been migrated into ItemHandler. 

Subclasses which wish to listen to combo box property changes should call the superclass methods to ensure that the combo popup correctly handles property changes. 

Also see:

getList
createList

Also see:

createScroller

Also see:

getMouseMotionListener
createMouseMotionListener

Also see:

getMouseListener
createMouseListener

Also see:

getKeyListener
createKeyListener

Also see:

createListSelectionListener

Also see:

createListMouseListener

Also see:

createListMouseMotionListener

Also see:

createPropertyChangeListener

Also see:

createListDataListener

Also see:

createItemListener

 public BasicComboPopup(JComboBox combo) 
{
        super();
        setName("ComboPopup.popup");
        comboBox = combo;
        setLightWeightPopupEnabled( comboBox.isLightWeightPopupEnabled() );
        // UI construction of the popup.
        list = createList();
        list.setName("ComboBox.list");
        configureList();
        scroller = createScroller();
        scroller.setName("ComboBox.scrollPane");
        configureScroller();
        configurePopup();
        installComboBoxListeners();
        installKeyboardActions();
}

 protected  void autoScrollDown() 
{
        int index = list.getSelectedIndex();
        int lastItem = list.getModel().getSize() - 1;
        if ( index <  lastItem ) {
            list.setSelectedIndex( index + 1 );
            list.ensureIndexIsVisible( index + 1 );
        }
}

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

 protected  void autoScrollUp() 
{
        int index = list.getSelectedIndex();
        if ( index  > 0 ) {
            list.setSelectedIndex( index - 1 );
            list.ensureIndexIsVisible( index - 1 );
        }
}

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

 protected Rectangle computePopupBounds(int px,
    int py,
    int pw,
    int ph) 
{
        Toolkit toolkit = Toolkit.getDefaultToolkit();
        Rectangle screenBounds;
        // Calculate the desktop dimensions relative to the combo box.
        GraphicsConfiguration gc = comboBox.getGraphicsConfiguration();
        Point p = new Point();
        SwingUtilities.convertPointFromScreen(p, comboBox);
        if (gc != null) {
            Insets screenInsets = toolkit.getScreenInsets(gc);
            screenBounds = gc.getBounds();
            screenBounds.width -= (screenInsets.left + screenInsets.right);
            screenBounds.height -= (screenInsets.top + screenInsets.bottom);
            screenBounds.x += (p.x + screenInsets.left);
            screenBounds.y += (p.y + screenInsets.top);
        }
        else {
            screenBounds = new Rectangle(p, toolkit.getScreenSize());
        }
        Rectangle rect = new Rectangle(px,py,pw,ph);
        if (py+ph  > screenBounds.y+screenBounds.height
            && ph <  screenBounds.height) {
            rect.y = -rect.height;
        }
        return rect;
}

Calculate the placement and size of the popup portion of the combo box based on the combo box location and the enclosing screen bounds. If no transformations are required, then the returned rectangle will have the same values as the parameters.

 protected  void configureList() 
{
        list.setFont( comboBox.getFont() );
        list.setForeground( comboBox.getForeground() );
        list.setBackground( comboBox.getBackground() );
        list.setSelectionForeground( UIManager.getColor( "ComboBox.selectionForeground" ) );
        list.setSelectionBackground( UIManager.getColor( "ComboBox.selectionBackground" ) );
        list.setBorder( null );
        list.setCellRenderer( comboBox.getRenderer() );
        list.setFocusable( false );
        list.setSelectionMode( ListSelectionModel.SINGLE_SELECTION );
        setListSelection( comboBox.getSelectedIndex() );
        installListListeners();
}

Configures the list which is used to hold the combo box items in the popup. This method is called when the UI class is created.

 protected  void configurePopup() 
{
        setLayout( new BoxLayout( this, BoxLayout.Y_AXIS ) );
        setBorderPainted( true );
        setBorder(LIST_BORDER);
        setOpaque( false );
        add( scroller );
        setDoubleBuffered( true );
        setFocusable( false );
}

Configures the popup portion of the combo box. This method is called when the UI class is created.

 protected  void configureScroller() 
{
        scroller.setFocusable( false );
        scroller.getVerticalScrollBar().setFocusable( false );
        scroller.setBorder( null );
}

Configures the scrollable portion which holds the list within the combo box popup. This method is called when the UI class is created.

 protected MouseEvent convertMouseEvent(MouseEvent e) 
{
        Point convertedPoint = SwingUtilities.convertPoint( (Component)e.getSource(),
                                                            e.getPoint(), list );
        MouseEvent newEvent = new MouseEvent( (Component)e.getSource(),
                                              e.getID(),
                                              e.getWhen(),
                                              e.getModifiers(),
                                              convertedPoint.x,
                                              convertedPoint.y,
                                              e.getXOnScreen(),
                                              e.getYOnScreen(),
                                              e.getClickCount(),
                                              e.isPopupTrigger(),
                                              MouseEvent.NOBUTTON );
        return newEvent;
}

 protected ItemListener createItemListener() 
{
        return getHandler();
}

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.

 protected KeyListener createKeyListener() 
{
        return null;
}

Creates the key listener that will be added to the combo box. If this method returns null then it will not be added to the combo box.

 protected JList createList() 
{
        return new JList( comboBox.getModel() ) {
            public void processMouseEvent(MouseEvent e)  {
                if (e.isControlDown())  {
                    // Fix for 4234053. Filter out the Control Key from the list.
                    // ie., don't allow CTRL key deselection.
                    e = new MouseEvent((Component)e.getSource(), e.getID(), e.getWhen(),
                                       e.getModifiers() ^ InputEvent.CTRL_MASK,
                                       e.getX(), e.getY(),
                                       e.getXOnScreen(), e.getYOnScreen(),
                                       e.getClickCount(),
                                       e.isPopupTrigger(),
                                       MouseEvent.NOBUTTON);
                }
                super.processMouseEvent(e);
            }
        };
}

Creates the JList used in the popup to display the items in the combo box model. This method is called when the UI class is created.

 protected ListDataListener createListDataListener() 
{
        return null;
}

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.

 protected MouseListener createListMouseListener() 
{
        return getHandler();
}

Creates a mouse listener that watches for mouse events in the popup's list. If this method returns null then it will not be added to the combo box.

 protected MouseMotionListener createListMouseMotionListener() 
{
        return getHandler();
}

Creates a mouse motion listener that watches for mouse motion events in the popup's list. If this method returns null then it will not be added to the combo box.

 protected ListSelectionListener createListSelectionListener() 
{
        return null;
}

Creates a list selection listener that watches for selection changes in the popup's list. If this method returns null then it will not be added to the popup list.

 protected MouseListener createMouseListener() 
{
        return getHandler();
}

Creates a listener that will watch for mouse-press and release events on the combo box. Warning: When overriding this method, make sure to maintain the existing behavior.

 protected MouseMotionListener createMouseMotionListener() 
{
        return getHandler();
}

Creates the mouse motion listener which will be added to the combo box. Warning: When overriding this method, make sure to maintain the existing behavior.

 protected PropertyChangeListener createPropertyChangeListener() 
{
        return getHandler();
}

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.

 protected JScrollPane createScroller() 
{
        JScrollPane sp = new JScrollPane( list,
                                ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED,
                                ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER );
        sp.setHorizontalScrollBar(null);
        return sp;
}

Creates the scroll pane which houses the scrollable list.

 protected  void delegateFocus(MouseEvent e) 
{
        if ( comboBox.isEditable() ) {
            Component comp = comboBox.getEditor().getEditorComponent();
            if ((!(comp instanceof JComponent)) || ((JComponent)comp).isRequestFocusEnabled()) {
                comp.requestFocus();
            }
        }
        else if (comboBox.isRequestFocusEnabled()) {
            comboBox.requestFocus();
        }
}

This is is a utility method that helps event handlers figure out where to send the focus when the popup is brought up. The standard implementation delegates the focus to the editor (if the combo box is editable) or to the JComboBox if it is not editable.

 protected  void firePopupMenuCanceled() 
{
        super.firePopupMenuCanceled();
        comboBox.firePopupMenuCanceled();
}

 protected  void firePopupMenuWillBecomeInvisible() 
{
        super.firePopupMenuWillBecomeInvisible();
        comboBox.firePopupMenuWillBecomeInvisible();
}

 protected  void firePopupMenuWillBecomeVisible() 
{
        super.firePopupMenuWillBecomeVisible();
        comboBox.firePopupMenuWillBecomeVisible();
}

 public AccessibleContext getAccessibleContext() 
{
        AccessibleContext context = super.getAccessibleContext();
        context.setAccessibleParent(comboBox);
        return context;
}

Gets the AccessibleContext associated with this BasicComboPopup. The AccessibleContext will have its parent set to the ComboBox.

 public KeyListener getKeyListener() 
{
        if (keyListener == null) {
            keyListener = createKeyListener();
        }
        return keyListener;
}

Implementation of ComboPopup.getKeyListener().

 public JList getList() 
{
        return list;
}

Implementation of ComboPopup.getList().

 public MouseListener getMouseListener() 
{
        if (mouseListener == null) {
            mouseListener = createMouseListener();
        }
        return mouseListener;
}

Implementation of ComboPopup.getMouseListener().

 public MouseMotionListener getMouseMotionListener() 
{
        if (mouseMotionListener == null) {
            mouseMotionListener = createMouseMotionListener();
        }
        return mouseMotionListener;
}

Implementation of ComboPopup.getMouseMotionListener().

 protected int getPopupHeightForRowCount(int maxRowCount) 
{
        // Set the cached value of the minimum row count
        int minRowCount = Math.min( maxRowCount, comboBox.getItemCount() );
        int height = 0;
        ListCellRenderer renderer = list.getCellRenderer();
        Object value = null;
        for ( int i = 0; i <  minRowCount; ++i ) {
            value = list.getModel().getElementAt( i );
            Component c = renderer.getListCellRendererComponent( list, value, i, false, false );
            height += c.getPreferredSize().height;
        }
        if (height == 0) {
            height = comboBox.getHeight();
        }
        Border border = scroller.getViewportBorder();
        if (border != null) {
            Insets insets = border.getBorderInsets(null);
            height += insets.top + insets.bottom;
        }
        border = scroller.getBorder();
        if (border != null) {
            Insets insets = border.getBorderInsets(null);
            height += insets.top + insets.bottom;
        }
        return height;
}

Retrieves the height of the popup based on the current ListCellRenderer and the maximum row count.

 public  void hide() 
{
        MenuSelectionManager manager = MenuSelectionManager.defaultManager();
        MenuElement [] selection = manager.getSelectedPath();
        for ( int i = 0 ; i <  selection.length ; i++ ) {
            if ( selection[i] == this ) {
                manager.clearSelectedPath();
                break;
            }
        }
        if (selection.length  > 0) {
            comboBox.repaint();
        }
}

Implementation of ComboPopup.hide().

 protected  void installComboBoxListeners() 
{
        if ((propertyChangeListener = createPropertyChangeListener()) != null) {
            comboBox.addPropertyChangeListener(propertyChangeListener);
        }
        if ((itemListener = createItemListener()) != null) {
            comboBox.addItemListener(itemListener);
        }
        installComboBoxModelListeners(comboBox.getModel());
}

This method adds the necessary listeners to the JComboBox.

 protected  void installComboBoxModelListeners(ComboBoxModel model) 
{
        if (model != null && (listDataListener = createListDataListener()) != null) {
            model.addListDataListener(listDataListener);
        }
}

Installs the listeners on the combo box model. Any listeners installed on the combo box model should be removed in uninstallComboBoxModelListeners.

 protected  void installKeyboardActions() 
{
        /* XXX - shouldn't call this method. take it out for testing.
        ActionListener action = new ActionListener() {
            public void actionPerformed(ActionEvent e){
            }
        };
        comboBox.registerKeyboardAction( action,
                                         KeyStroke.getKeyStroke( KeyEvent.VK_ENTER, 0 ),
                                         JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT ); */
}

 protected  void installListListeners() 
{
        if ((listMouseListener = createListMouseListener()) != null) {
            list.addMouseListener( listMouseListener );
        }
        if ((listMouseMotionListener = createListMouseMotionListener()) != null) {
            list.addMouseMotionListener( listMouseMotionListener );
        }
        if ((listSelectionListener = createListSelectionListener()) != null) {
            list.addListSelectionListener( listSelectionListener );
        }
}

Adds the listeners to the list control.

 public boolean isFocusTraversable() 
{
        return false;
}

Overridden to unconditionally return false.

 public  void show() 
{
    //========================================
    // begin ComboPopup method implementations
    //
        setListSelection(comboBox.getSelectedIndex());
        Point location = getPopupLocation();
        show( comboBox, location.x, location.y );
}

Implementation of ComboPopup.show().

 protected  void startAutoScrolling(int direction) 
{
        // XXX - should be a private method within InvocationMouseMotionHandler
        // if possible.
        if ( isAutoScrolling ) {
            autoscrollTimer.stop();
        }
        isAutoScrolling = true;
        if ( direction == SCROLL_UP ) {
            scrollDirection = SCROLL_UP;
            Point convertedPoint = SwingUtilities.convertPoint( scroller, new Point( 1, 1 ), list );
            int top = list.locationToIndex( convertedPoint );
            list.setSelectedIndex( top );
            autoscrollTimer = new Timer( 100, new AutoScrollActionHandler(
                                             SCROLL_UP) );
        }
        else if ( direction == SCROLL_DOWN ) {
            scrollDirection = SCROLL_DOWN;
            Dimension size = scroller.getSize();
            Point convertedPoint = SwingUtilities.convertPoint( scroller,
                                                                new Point( 1, (size.height - 1) - 2 ),
                                                                list );
            int bottom = list.locationToIndex( convertedPoint );
            list.setSelectedIndex( bottom );
            autoscrollTimer = new Timer(100, new AutoScrollActionHandler(
                                            SCROLL_DOWN));
        }
        autoscrollTimer.start();
}

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

 protected  void stopAutoScrolling() 
{
        isAutoScrolling = false;
        if ( autoscrollTimer != null ) {
            autoscrollTimer.stop();
            autoscrollTimer = null;
        }
}

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

 protected  void togglePopup() 
{
        if ( isVisible() ) {
            hide();
        }
        else {
            show();
        }
}

Makes the popup visible if it is hidden and makes it hidden if it is visible.

 protected  void uninstallComboBoxModelListeners(ComboBoxModel model) 
{
        if (model != null && listDataListener != null) {
            model.removeListDataListener(listDataListener);
        }
}

Removes the listeners from the combo box model

 protected  void uninstallKeyboardActions() 
{
        // XXX - shouldn't call this method
//        comboBox.unregisterKeyboardAction( KeyStroke.getKeyStroke( KeyEvent.VK_ENTER, 0 ) );
}

  void uninstallListListeners() 
{
        if (listMouseListener != null) {
            list.removeMouseListener(listMouseListener);
            listMouseListener = null;
        }
        if (listMouseMotionListener != null) {
            list.removeMouseMotionListener(listMouseMotionListener);
            listMouseMotionListener = null;
        }
        if (listSelectionListener != null) {
            list.removeListSelectionListener(listSelectionListener);
            listSelectionListener = null;
        }
        handler = null;
}

 public  void uninstallingUI() 
{
        if (propertyChangeListener != null) {
            comboBox.removePropertyChangeListener( propertyChangeListener );
        }
        if (itemListener != null) {
            comboBox.removeItemListener( itemListener );
        }
        uninstallComboBoxModelListeners(comboBox.getModel());
        uninstallKeyboardActions();
        uninstallListListeners();
        // We do this, otherwise the listener the ui installs on
        // the model (the combobox model in this case) will keep a
        // reference to the list, causing the list (and us) to never get gced.
        list.setModel(EmptyListModel);
}

Called when the UI is uninstalling. Since this popup isn't in the component tree, it won't get it's uninstallUI() called. It removes the listeners that were added in addComboBoxListeners().

 protected  void updateListBoxSelectionForEvent(MouseEvent anEvent,
    boolean shouldScroll) 
{
        // XXX - only seems to be called from this class. shouldScroll flag is
        // never true
        Point location = anEvent.getPoint();
        if ( list == null )
            return;
        int index = list.locationToIndex(location);
        if ( index == -1 ) {
            if ( location.y <  0 )
                index = 0;
            else
                index = comboBox.getModel().getSize() - 1;
        }
        if ( list.getSelectedIndex() != index ) {
            list.setSelectedIndex(index);
            if ( shouldScroll )
                list.ensureIndexIsVisible(index);
        }
}

A utility method used by the event listeners. Given a mouse event, it changes the list selection to the list item below the mouse.