Class FixedJComboBox<E>
- All Implemented Interfaces:
ActionListener
,ImageObserver
,ItemSelectable
,MenuContainer
,Serializable
,EventListener
,Accessible
,ListDataListener
- Direct Known Subclasses:
ColumnDataComboBox
The problem is to do with firing ActionEvents when the
ComboBoxModel is changed.
According to the JComboBox.addActionListener(java.awt.event.ActionListener)
documentation, ActionListeners should only be informed when a
selection is made, that is when the selection changes.
In general that's true, an ActionEvent is only fired when the
model selection changes, but at least in Oracle Java 8/OpenJDK 8
such an event can be fired if the model content (list data) changes
but the current selection is null both before and after that change
(if the selection is an particular non-null value before and after,
no ActionEvent is fired, as expected).
Since there are a lot of listeners on these selectors in topcat,
and certain user actions can cause a large number of changes to
the model without changing the selection, this can cause a lot of
unnecessary events to be fired, which can in some circumstances
result in genuine responsiveness issues.
This class overrides the contentsChanged(javax.swing.event.ListDataEvent)
method,
and enough other methods to make that work, so that no event is fired
in the event of a null->null selection change.
- Since:
- 6 Oct 2023
- Author:
- Mark Taylor
- See Also:
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Nested Class Summary
Nested classes/interfaces inherited from class javax.swing.JComboBox
JComboBox.AccessibleJComboBox, JComboBox.KeySelectionManager
Nested classes/interfaces inherited from class javax.swing.JComponent
JComponent.AccessibleJComponent
Nested classes/interfaces inherited from class java.awt.Container
Container.AccessibleAWTContainer
Nested classes/interfaces inherited from class java.awt.Component
Component.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy
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Field Summary
Fields inherited from class javax.swing.JComboBox
actionCommand, dataModel, editor, isEditable, keySelectionManager, lightWeightPopupEnabled, maximumRowCount, renderer, selectedItemReminder
Fields inherited from class javax.swing.JComponent
listenerList, TOOL_TIP_TEXT_KEY, ui, UNDEFINED_CONDITION, WHEN_ANCESTOR_OF_FOCUSED_COMPONENT, WHEN_FOCUSED, WHEN_IN_FOCUSED_WINDOW
Fields inherited from class java.awt.Component
accessibleContext, BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT
Fields inherited from interface java.awt.image.ImageObserver
ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH
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Constructor Summary
ConstructorsConstructorDescriptionCreates a JComboBox with a default data model.FixedJComboBox
(E[] items) Creates a JComboBox that contains the elements in the specified array.FixedJComboBox
(ComboBoxModel<E> model) Creates a JComboBox that takes its items from an existing ComboBoxModel. -
Method Summary
Modifier and TypeMethodDescriptionvoid
Overriding this method is questionable, since the OpenJDK javadoc says: "This method is public as an implementation side effect.void
protected void
void
setModel
(ComboBoxModel<E> model) Methods inherited from class javax.swing.JComboBox
actionPerformed, actionPropertyChanged, addActionListener, addItem, addItemListener, addPopupMenuListener, configureEditor, configurePropertiesFromAction, createActionPropertyChangeListener, createDefaultKeySelectionManager, fireActionEvent, fireItemStateChanged, firePopupMenuCanceled, firePopupMenuWillBecomeInvisible, firePopupMenuWillBecomeVisible, getAccessibleContext, getAction, getActionCommand, getActionListeners, getEditor, getItemAt, getItemCount, getItemListeners, getKeySelectionManager, getMaximumRowCount, getModel, getPopupMenuListeners, getPrototypeDisplayValue, getRenderer, getSelectedIndex, getSelectedItem, getSelectedObjects, getUI, getUIClassID, hidePopup, insertItemAt, installAncestorListener, intervalAdded, intervalRemoved, isEditable, isLightWeightPopupEnabled, isPopupVisible, paramString, processKeyBinding, processKeyEvent, removeActionListener, removeItem, removeItemAt, removeItemListener, removePopupMenuListener, selectWithKeyChar, setAction, setActionCommand, setEditable, setEditor, setEnabled, setKeySelectionManager, setLightWeightPopupEnabled, setMaximumRowCount, setPopupVisible, setPrototypeDisplayValue, setRenderer, setSelectedIndex, setSelectedItem, setUI, showPopup, updateUI
Methods inherited from class javax.swing.JComponent
addAncestorListener, addNotify, addVetoableChangeListener, computeVisibleRect, contains, createToolTip, disable, enable, firePropertyChange, 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, hide, isDoubleBuffered, isLightweightComponent, isManagingFocus, isOpaque, isOptimizedDrawingEnabled, isPaintingForPrint, isPaintingOrigin, isPaintingTile, isRequestFocusEnabled, isValidateRoot, paint, paintBorder, paintChildren, paintComponent, paintImmediately, paintImmediately, print, printAll, printBorder, printChildren, printComponent, processComponentKeyEvent, 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, setFocusTraversalKeys, setFont, setForeground, setInheritsPopupMenu, setInputMap, setInputVerifier, setMaximumSize, setMinimumSize, setNextFocusableComponent, setOpaque, setPreferredSize, setRequestFocusEnabled, setToolTipText, setTransferHandler, setUI, setVerifyInputWhenFocusTarget, setVisible, unregisterKeyboardAction, update
Methods inherited from 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, remove, removeAll, removeContainerListener, setComponentZOrder, setFocusCycleRoot, setFocusTraversalPolicy, setFocusTraversalPolicyProvider, setLayout, transferFocusDownCycle, validate, validateTree
Methods inherited from 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, 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, isFocusTraversable, isFontSet, isForegroundSet, isLightweight, isMaximumSizeSet, isMinimumSizeSet, isPreferredSizeSet, isShowing, isValid, isVisible, 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, setLocation, setMixingCutoutShape, setName, setSize, setSize, show, show, size, toString, transferFocus, transferFocusBackward, transferFocusUpCycle
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Constructor Details
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FixedJComboBox
public FixedJComboBox()Creates a JComboBox with a default data model. -
FixedJComboBox
Creates a JComboBox that takes its items from an existing ComboBoxModel.- Parameters:
model
- model
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FixedJComboBox
Creates a JComboBox that contains the elements in the specified array.- Parameters:
items
- array populating default combo box model
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Method Details
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contentsChanged
Overriding this method is questionable, since the OpenJDK javadoc says: "This method is public as an implementation side effect. do not call or override.". So there could be problems. But if the method exists at all to be overridden, this implementation shouldn't change its behaviour in a bad way, and if it doesn't exist it shouldn't have any effect, so I don't *expect* runtime problems with either OpenJDK or other JDKs.However if an attempt is made to compile this class against a JDK in which JComboBox lacks the
contentsChanged
method, there will be trouble. It could be averted by removing the@Override
annotation, and invoking the superclass method using reflection.- Specified by:
contentsChanged
in interfaceListDataListener
- Overrides:
contentsChanged
in classJComboBox<E>
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setModel
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removeAllItems
public void removeAllItems()- Overrides:
removeAllItems
in classJComboBox<E>
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selectedItemChanged
protected void selectedItemChanged()- Overrides:
selectedItemChanged
in classJComboBox<E>
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