- All Implemented Interfaces:
ImageObserver
,MenuContainer
,Serializable
,Accessible
,MenuElement
,ComboPopup
- Direct Known Subclasses:
MetalComboBoxUI.MetalComboPopup
public class BasicComboPopup extends JPopupMenu implements ComboPopup
ComboPopup
interface.
This class represents the ui for the popup portion 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.
Warning:
Serialized objects of this class will not be compatible with
future Swing releases. The current serialization support is
appropriate for short term storage or RMI between applications running
the same version of Swing. As of 1.4, support for long term storage
of all JavaBeans
has been added to the java.beans
package.
Please see XMLEncoder
.
-
Nested Class Summary
Nested Classes Modifier and Type Class Description class
BasicComboPopup.InvocationKeyHandler
As of Java 2 platform v 1.4, this class is now obsolete and is only included for backwards API compatibility.protected class
BasicComboPopup.InvocationMouseHandler
A listener to be registered upon the combo box (not its popup menu) to handle mouse events that affect the state of the popup menu.protected class
BasicComboPopup.InvocationMouseMotionHandler
This listener watches for dragging and updates the current selection in the list if it is dragging over the list.protected class
BasicComboPopup.ItemHandler
This listener watches for changes to the selection in the combo box.class
BasicComboPopup.ListDataHandler
As of 1.4, this class is now obsolete, doesn't do anything, and is only included for backwards API compatibility.protected class
BasicComboPopup.ListMouseHandler
This listener hides the popup when the mouse is released in the list.protected class
BasicComboPopup.ListMouseMotionHandler
This listener changes the selected item as you move the mouse over the list.protected class
BasicComboPopup.ListSelectionHandler
As of Java 2 platform v 1.4, this class is now obsolete, doesn't do anything, and is only included for backwards API compatibility.protected class
BasicComboPopup.PropertyChangeHandler
This listener watches for bound properties that have changed in the combo box.Nested classes/interfaces declared in class javax.swing.JPopupMenu
JPopupMenu.AccessibleJPopupMenu, JPopupMenu.Separator
Nested classes/interfaces declared in class javax.swing.JComponent
JComponent.AccessibleJComponent
Nested classes/interfaces declared in class java.awt.Container
Container.AccessibleAWTContainer
Nested classes/interfaces declared in class java.awt.Component
Component.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy
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Field Summary
Fields Modifier and Type Field Description protected Timer
autoscrollTimer
This protected field is implementation specific.protected JComboBox<Object>
comboBox
The instance ofJComboBox
.protected boolean
hasEntered
true
if the mouse cursor is in the popup.protected boolean
isAutoScrolling
Iftrue
the auto-scrolling is enabled.protected ItemListener
itemListener
This protected field is implementation specific.protected KeyListener
keyListener
This protected field is implementation specific.protected JList<Object>
list
This protected field is implementation specific.protected ListDataListener
listDataListener
This protected field is implementation specific.protected MouseListener
listMouseListener
This protected field is implementation specific.protected MouseMotionListener
listMouseMotionListener
This protected field is implementation specific.protected ListSelectionListener
listSelectionListener
This protected field is implementation specific.protected MouseListener
mouseListener
This protected field is implementation specific.protected MouseMotionListener
mouseMotionListener
This protected field is implementation specific.protected PropertyChangeListener
propertyChangeListener
This protected field is implementation specific.protected static int
SCROLL_DOWN
The direction of scrolling down.protected static int
SCROLL_UP
The direction of scrolling up.protected int
scrollDirection
The direction of scrolling.protected JScrollPane
scroller
This protected field is implementation specific.protected boolean
valueIsAdjusting
As of Java 2 platform v1.4 this previously undocumented field is no longer used.Fields declared in class javax.swing.JComponent
listenerList, TOOL_TIP_TEXT_KEY, ui, UNDEFINED_CONDITION, WHEN_ANCESTOR_OF_FOCUSED_COMPONENT, WHEN_FOCUSED, WHEN_IN_FOCUSED_WINDOW
Fields declared in class java.awt.Component
accessibleContext, BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT
Fields declared in interface java.awt.image.ImageObserver
ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH
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Constructor Summary
Constructors Constructor Description BasicComboPopup(JComboBox<Object> combo)
Constructs a new instance ofBasicComboPopup
. -
Method Summary
Modifier and Type Method Description protected void
autoScrollDown()
This protected method is implementation specific and should be private.protected void
autoScrollUp()
This protected method is implementation specific and should be private.protected Rectangle
computePopupBounds(int px, int py, int pw, int ph)
Calculate the placement and size of the popup portion of the combo box based on the combo box location and the enclosing screen bounds.protected void
configureList()
Configures the list which is used to hold the combo box items in the popup.protected void
configurePopup()
Configures the popup portion of the combo box.protected void
configureScroller()
Configures the scrollable portion which holds the list within the combo box popup.protected MouseEvent
convertMouseEvent(MouseEvent e)
Converts mouse event.protected ItemListener
createItemListener()
Creates anItemListener
which will be added to the combo box.protected KeyListener
createKeyListener()
Creates the key listener that will be added to the combo box.protected JList<Object>
createList()
Creates the JList used in the popup to display the items in the combo box model.protected ListDataListener
createListDataListener()
Creates a list data listener which will be added to theComboBoxModel
.protected MouseListener
createListMouseListener()
Creates a mouse listener that watches for mouse events in the popup's list.protected MouseMotionListener
createListMouseMotionListener()
Creates a mouse motion listener that watches for mouse motion events in the popup's list.protected ListSelectionListener
createListSelectionListener()
Creates a list selection listener that watches for selection changes in the popup's list.protected MouseListener
createMouseListener()
Creates a listener that will watch for mouse-press and release events on the combo box.protected MouseMotionListener
createMouseMotionListener()
Creates the mouse motion listener which will be added to the combo box.protected PropertyChangeListener
createPropertyChangeListener()
Creates aPropertyChangeListener
which will be added to the combo box.protected JScrollPane
createScroller()
Creates the scroll pane which houses the scrollable list.protected void
delegateFocus(MouseEvent e)
This is a utility method that helps event handlers figure out where to send the focus when the popup is brought up.AccessibleContext
getAccessibleContext()
Gets the AccessibleContext associated with this BasicComboPopup.KeyListener
getKeyListener()
Implementation of ComboPopup.getKeyListener().JList<Object>
getList()
Implementation of ComboPopup.getList().MouseListener
getMouseListener()
Implementation of ComboPopup.getMouseListener().MouseMotionListener
getMouseMotionListener()
Implementation of ComboPopup.getMouseMotionListener().protected int
getPopupHeightForRowCount(int maxRowCount)
Retrieves the height of the popup based on the current ListCellRenderer and the maximum row count.void
hide()
Implementation of ComboPopup.hide().protected void
installComboBoxListeners()
This method adds the necessary listeners to the JComboBox.protected void
installComboBoxModelListeners(ComboBoxModel<?> model)
Installs the listeners on the combo box model.protected void
installKeyboardActions()
Registers keyboard actions.protected void
installListListeners()
Adds the listeners to the list control.boolean
isFocusTraversable()
Overridden to unconditionally return false.void
show()
Implementation of ComboPopup.show().protected void
startAutoScrolling(int direction)
This protected method is implementation specific and should be private.protected void
stopAutoScrolling()
This protected method is implementation specific and should be private.protected void
togglePopup()
Makes the popup visible if it is hidden and makes it hidden if it is visible.protected void
uninstallComboBoxModelListeners(ComboBoxModel<?> model)
Removes the listeners from the combo box modelvoid
uninstallingUI()
Called when the UI is uninstalling.protected void
uninstallKeyboardActions()
Unregisters keyboard actions.protected void
updateListBoxSelectionForEvent(MouseEvent anEvent, boolean shouldScroll)
A utility method used by the event listeners.Methods declared in class javax.swing.JPopupMenu
add, add, add, addMenuKeyListener, addPopupMenuListener, addSeparator, createActionChangeListener, createActionComponent, firePopupMenuCanceled, firePopupMenuWillBecomeInvisible, firePopupMenuWillBecomeVisible, getComponent, getComponentAtIndex, getComponentIndex, getDefaultLightWeightPopupEnabled, getInvoker, getLabel, getMargin, getMenuKeyListeners, getPopupMenuListeners, getSelectionModel, getSubElements, getUI, getUIClassID, insert, insert, isBorderPainted, isLightWeightPopupEnabled, isPopupTrigger, isVisible, menuSelectionChanged, pack, paintBorder, paramString, processKeyEvent, processKeyEvent, processMouseEvent, remove, removeMenuKeyListener, removePopupMenuListener, setBorderPainted, setDefaultLightWeightPopupEnabled, setInvoker, setLabel, setLightWeightPopupEnabled, setLocation, setPopupSize, setPopupSize, setSelected, setSelectionModel, setUI, setVisible, show, updateUI
Methods declared in class javax.swing.JComponent
addAncestorListener, addNotify, addVetoableChangeListener, computeVisibleRect, contains, createToolTip, disable, enable, firePropertyChange, firePropertyChange, fireVetoableChange, getActionForKeyStroke, getActionMap, getAlignmentX, getAlignmentY, getAncestorListeners, getAutoscrolls, getBaseline, getBaselineResizeBehavior, getBorder, getBounds, getClientProperty, getComponentGraphics, getComponentPopupMenu, getConditionForKeyStroke, getDebugGraphicsOptions, getDefaultLocale, getFontMetrics, getGraphics, getHeight, getInheritsPopupMenu, getInputMap, getInputMap, getInputVerifier, getInsets, getInsets, getListeners, getLocation, getMaximumSize, getMinimumSize, getNextFocusableComponent, getPopupLocation, getPreferredSize, getRegisteredKeyStrokes, getRootPane, getSize, getToolTipLocation, getToolTipText, getToolTipText, getTopLevelAncestor, getTransferHandler, getVerifyInputWhenFocusTarget, getVetoableChangeListeners, getVisibleRect, getWidth, getX, getY, grabFocus, isDoubleBuffered, isLightweightComponent, isManagingFocus, isOpaque, isOptimizedDrawingEnabled, isPaintingForPrint, isPaintingOrigin, isPaintingTile, isRequestFocusEnabled, isValidateRoot, paint, paintChildren, paintComponent, paintImmediately, paintImmediately, print, printAll, printBorder, printChildren, printComponent, processComponentKeyEvent, processKeyBinding, processMouseEvent, processMouseMotionEvent, putClientProperty, registerKeyboardAction, registerKeyboardAction, removeAncestorListener, removeNotify, removeVetoableChangeListener, repaint, repaint, requestDefaultFocus, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, resetKeyboardActions, reshape, revalidate, scrollRectToVisible, setActionMap, setAlignmentX, setAlignmentY, setAutoscrolls, setBackground, setBorder, setComponentPopupMenu, setDebugGraphicsOptions, setDefaultLocale, setDoubleBuffered, setEnabled, setFocusTraversalKeys, setFont, setForeground, setInheritsPopupMenu, setInputMap, setInputVerifier, setMaximumSize, setMinimumSize, setNextFocusableComponent, setOpaque, setPreferredSize, setRequestFocusEnabled, setToolTipText, setTransferHandler, setUI, setVerifyInputWhenFocusTarget, unregisterKeyboardAction, update
Methods declared in class java.awt.Container
add, add, add, add, add, addContainerListener, addImpl, addPropertyChangeListener, addPropertyChangeListener, applyComponentOrientation, areFocusTraversalKeysSet, countComponents, deliverEvent, doLayout, findComponentAt, findComponentAt, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getComponentZOrder, getContainerListeners, getFocusTraversalKeys, getFocusTraversalPolicy, getLayout, getMousePosition, insets, invalidate, isAncestorOf, isFocusCycleRoot, isFocusCycleRoot, isFocusTraversalPolicyProvider, isFocusTraversalPolicySet, layout, list, list, locate, minimumSize, paintComponents, preferredSize, printComponents, processContainerEvent, processEvent, remove, removeAll, removeContainerListener, setComponentZOrder, setFocusCycleRoot, setFocusTraversalPolicy, setFocusTraversalPolicyProvider, setLayout, transferFocusDownCycle, validate, validateTree
Methods declared in class java.awt.Component
action, add, addComponentListener, addFocusListener, addHierarchyBoundsListener, addHierarchyListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addMouseWheelListener, bounds, checkImage, checkImage, coalesceEvents, contains, createImage, createImage, createVolatileImage, createVolatileImage, disableEvents, dispatchEvent, enable, enableEvents, enableInputMethods, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, getBackground, getBounds, getColorModel, getComponentListeners, getComponentOrientation, getCursor, getDropTarget, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeysEnabled, getFont, getForeground, getGraphicsConfiguration, getHierarchyBoundsListeners, getHierarchyListeners, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, getLocale, getLocation, getLocationOnScreen, getMouseListeners, getMouseMotionListeners, getMousePosition, getMouseWheelListeners, getName, getParent, getPropertyChangeListeners, getPropertyChangeListeners, getSize, getToolkit, getTreeLock, gotFocus, handleEvent, hasFocus, imageUpdate, inside, isBackgroundSet, isCursorSet, isDisplayable, isEnabled, isFocusable, isFocusOwner, isFontSet, isForegroundSet, isLightweight, isMaximumSizeSet, isMinimumSizeSet, isPreferredSizeSet, isShowing, isValid, keyDown, keyUp, list, list, list, location, lostFocus, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, postEvent, prepareImage, prepareImage, processComponentEvent, processFocusEvent, processHierarchyBoundsEvent, processHierarchyEvent, processInputMethodEvent, processMouseWheelEvent, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeMouseWheelListener, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, requestFocus, requestFocus, requestFocusInWindow, resize, resize, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setFocusable, setFocusTraversalKeysEnabled, setIgnoreRepaint, setLocale, setLocation, setMixingCutoutShape, setName, setSize, setSize, show, size, toString, transferFocus, transferFocusBackward, transferFocusUpCycle
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Methods declared in interface javax.swing.plaf.basic.ComboPopup
isVisible
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Field Details
-
comboBox
The instance ofJComboBox
. -
list
This protected field is implementation specific. Do not access directly or override. Use the accessor methods instead.- See Also:
getList()
,createList()
-
scroller
This protected field is implementation specific. Do not access directly or override. Use the create method instead- See Also:
createScroller()
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valueIsAdjusting
protected boolean valueIsAdjustingAs of Java 2 platform v1.4 this previously undocumented field is no longer used. -
mouseMotionListener
This protected field is implementation specific. Do not access directly or override. Use the accessor or create methods instead. -
mouseListener
This protected field is implementation specific. Do not access directly or override. Use the accessor or create methods instead.- See Also:
getMouseListener()
,createMouseListener()
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keyListener
This protected field is implementation specific. Do not access directly or override. Use the accessor or create methods instead.- See Also:
getKeyListener()
,createKeyListener()
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listSelectionListener
This protected field is implementation specific. Do not access directly or override. Use the create method instead.- See Also:
createListSelectionListener()
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listMouseListener
This protected field is implementation specific. Do not access directly or override. Use the create method instead.- See Also:
createListMouseListener()
-
listMouseMotionListener
This protected field is implementation specific. Do not access directly or override. Use the create method instead- See Also:
createListMouseMotionListener()
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propertyChangeListener
This protected field is implementation specific. Do not access directly or override. Use the create method instead- See Also:
createPropertyChangeListener()
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listDataListener
This protected field is implementation specific. Do not access directly or override. Use the create method instead- See Also:
createListDataListener()
-
itemListener
This protected field is implementation specific. Do not access directly or override. Use the create method instead- See Also:
createItemListener()
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autoscrollTimer
This protected field is implementation specific. Do not access directly or override. -
hasEntered
protected boolean hasEnteredtrue
if the mouse cursor is in the popup. -
isAutoScrolling
protected boolean isAutoScrollingIftrue
the auto-scrolling is enabled. -
scrollDirection
protected int scrollDirectionThe direction of scrolling. -
SCROLL_UP
protected static final int SCROLL_UPThe direction of scrolling up.- See Also:
- Constant Field Values
-
SCROLL_DOWN
protected static final int SCROLL_DOWNThe direction of scrolling down.- See Also:
- Constant Field Values
-
-
Constructor Details
-
BasicComboPopup
Constructs a new instance ofBasicComboPopup
.- Parameters:
combo
- an instance ofJComboBox
-
-
Method Details
-
show
public void show()Implementation of ComboPopup.show().- Specified by:
show
in interfaceComboPopup
- Overrides:
show
in classComponent
-
hide
public void hide()Implementation of ComboPopup.hide().- Specified by:
hide
in interfaceComboPopup
- Overrides:
hide
in classJComponent
-
getList
Implementation of ComboPopup.getList().- Specified by:
getList
in interfaceComboPopup
- Returns:
- the list that is being used to draw the items in the combo box
-
getMouseListener
Implementation of ComboPopup.getMouseListener().- Specified by:
getMouseListener
in interfaceComboPopup
- Returns:
- a
MouseListener
or null - See Also:
ComboPopup.getMouseListener()
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getMouseMotionListener
Implementation of ComboPopup.getMouseMotionListener().- Specified by:
getMouseMotionListener
in interfaceComboPopup
- Returns:
- a
MouseMotionListener
or null - See Also:
ComboPopup.getMouseMotionListener()
-
getKeyListener
Implementation of ComboPopup.getKeyListener().- Specified by:
getKeyListener
in interfaceComboPopup
- Returns:
- a
KeyListener
or null - See Also:
ComboPopup.getKeyListener()
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uninstallingUI
public void uninstallingUI()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().- Specified by:
uninstallingUI
in interfaceComboPopup
-
uninstallComboBoxModelListeners
Removes the listeners from the combo box model- Parameters:
model
- The combo box model to install listeners- See Also:
installComboBoxModelListeners(javax.swing.ComboBoxModel<?>)
-
uninstallKeyboardActions
protected void uninstallKeyboardActions()Unregisters keyboard actions. -
createMouseListener
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.- Returns:
- a
MouseListener
which will be added to the combo box or null
-
createMouseMotionListener
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.- Returns:
- a
MouseMotionListener
which will be added to the combo box or null
-
createKeyListener
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.- Returns:
- a
KeyListener
or null
-
createListSelectionListener
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.- Returns:
- an instance of a
ListSelectionListener
or null
-
createListDataListener
Creates a list data listener which will be added to theComboBoxModel
. If this method returns null then it will not be added to the combo box model.- Returns:
- an instance of a
ListDataListener
or null
-
createListMouseListener
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.- Returns:
- an instance of a
MouseListener
or null
-
createListMouseMotionListener
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.- Returns:
- an instance of a
MouseMotionListener
or null
-
createPropertyChangeListener
Creates aPropertyChangeListener
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
-
createItemListener
Creates anItemListener
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
-
createList
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.- Returns:
- a
JList
used to display the combo box items
-
configureList
protected void configureList()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.- See Also:
createList()
-
installListListeners
protected void installListListeners()Adds the listeners to the list control. -
createScroller
Creates the scroll pane which houses the scrollable list.- Returns:
- the scroll pane which houses the scrollable list
-
configureScroller
protected void configureScroller()Configures the scrollable portion which holds the list within the combo box popup. This method is called when the UI class is created. -
configurePopup
protected void configurePopup()Configures the popup portion of the combo box. This method is called when the UI class is created. -
installComboBoxListeners
protected void installComboBoxListeners()This method adds the necessary listeners to the JComboBox. -
installComboBoxModelListeners
Installs the listeners on the combo box model. Any listeners installed on the combo box model should be removed inuninstallComboBoxModelListeners
.- Parameters:
model
- The combo box model to install listeners- See Also:
uninstallComboBoxModelListeners(javax.swing.ComboBoxModel<?>)
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installKeyboardActions
protected void installKeyboardActions()Registers keyboard actions. -
isFocusTraversable
public boolean isFocusTraversable()Overridden to unconditionally return false.- Overrides:
isFocusTraversable
in classComponent
- Returns:
true
if thisComponent
is focusable;false
otherwise- See Also:
Component.setFocusable(boolean)
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startAutoScrolling
protected void startAutoScrolling(int direction)This protected method is implementation specific and should be private. do not call or override.- Parameters:
direction
- the direction of scrolling
-
stopAutoScrolling
protected void stopAutoScrolling()This protected method is implementation specific and should be private. do not call or override. -
autoScrollUp
protected void autoScrollUp()This protected method is implementation specific and should be private. do not call or override. -
autoScrollDown
protected void autoScrollDown()This protected method is implementation specific and should be private. do not call or override. -
getAccessibleContext
Gets the AccessibleContext associated with this BasicComboPopup. The AccessibleContext will have its parent set to the ComboBox.- Specified by:
getAccessibleContext
in interfaceAccessible
- Overrides:
getAccessibleContext
in classJPopupMenu
- Returns:
- an AccessibleContext for the BasicComboPopup
- Since:
- 1.5
-
delegateFocus
This 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.- Parameters:
e
- a mouse event
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togglePopup
protected void togglePopup()Makes the popup visible if it is hidden and makes it hidden if it is visible. -
convertMouseEvent
Converts mouse event.- Parameters:
e
- a mouse event- Returns:
- converted mouse event
-
getPopupHeightForRowCount
protected int getPopupHeightForRowCount(int maxRowCount)Retrieves the height of the popup based on the current ListCellRenderer and the maximum row count.- Parameters:
maxRowCount
- the row count- Returns:
- the height of the popup
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computePopupBounds
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.- Parameters:
px
- starting x locationpy
- starting y locationpw
- starting widthph
- starting height- Returns:
- a rectangle which represents the placement and size of the popup
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updateListBoxSelectionForEvent
A utility method used by the event listeners. Given a mouse event, it changes the list selection to the list item below the mouse.- Parameters:
anEvent
- a mouse eventshouldScroll
- iftrue
list should be scrolled.
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