JList (Java Platform SE 6) - JDK 5 Documentation v6.0, Java 2 SDK 英文文档

javax.swing
Class JList

java.lang.Object
  java.awt.Component
      java.awt.Container
          javax.swing.JComponent
              javax.swing.JList

All Implemented Interfaces:

ImageObserver, MenuContainer, Serializable, Accessible, Scrollable

public class JList
extends JComponent
implements Scrollable, Accessible

A component that displays a list of objects and allows the user to select one or more items. A separate model, ListModel, maintains the contents of the list.

It's easy to display an array or Vector of objects, using the JList constructor that automatically builds a read-only ListModel instance for you:

 // Create a JList that displays strings from an array

 String[] data = {"one", "two", "three", "four"};
 JList myList = new JList(data);

 // Create a JList that displays the superclasses of JList.class, by
 // creating it with a Vector populated with this data

 Vector superClasses = new Vector();
 Class rootClass = javax.swing.JList.class;
 for(Class cls = rootClass; cls != null; cls = cls.getSuperclass()) {
     superClasses.addElement(cls);
 }
 JList myList = new JList(superClasses);
 
 // The automatically created model is stored in JList's "model"
 // property, which you can retrieve

 ListModel model = myList.getModel();
 for(int i = 0; i < model.getSize(); i++) {
     System.out.println(model.getElementAt(i));
 }
 

A ListModel can be supplied directly to a JList by way of a constructor or the setModel method. The contents need not be static - the number of items, and the values of items can change over time. A correct ListModel implementation notifies the set of javax.swing.event.ListDataListeners that have been added to it, each time a change occurs. These changes are characterized by a javax.swing.event.ListDataEvent, which identifies the range of list indices that have been modified, added, or removed. JList's ListUI is responsible for keeping the visual representation up to date with changes, by listening to the model.

Simple, dynamic-content, JList applications can use the DefaultListModel class to maintain list elements. This class implements the ListModel interface and also provides a java.util.Vector-like API. Applications that need a more custom ListModel implementation may instead wish to subclass AbstractListModel, which provides basic support for managing and notifying listeners. For example, a read-only implementation of AbstractListModel:

 // This list model has about 2^16 elements.  Enjoy scrolling.

 ListModel bigData = new AbstractListModel() {
     public int getSize() { return Short.MAX_VALUE; }
     public Object getElementAt(int index) { return "Index " + index; }
 };
 

The selection state of a JList is managed by another separate model, an instance of ListSelectionModel. JList is initialized with a selection model on construction, and also contains methods to query or set this selection model. Additionally, JList provides convenient methods for easily managing the selection. These methods, such as setSelectedIndex and getSelectedValue, are cover methods that take care of the details of interacting with the selection model. By default, JList's selection model is configured to allow any combination of items to be selected at a time; selection mode MULTIPLE_INTERVAL_SELECTION. The selection mode can be changed on the selection model directly, or via JList's cover method. Responsibility for updating the selection model in response to user gestures lies with the list's ListUI.

A correct ListSelectionModel implementation notifies the set of javax.swing.event.ListSelectionListeners that have been added to it each time a change to the selection occurs. These changes are characterized by a javax.swing.event.ListSelectionEvent, which identifies the range of the selection change.

The preferred way to listen for changes in list selection is to add ListSelectionListeners directly to the JList. JList then takes care of listening to the the selection model and notifying your listeners of change.

Responsibility for listening to selection changes in order to keep the list's visual representation up to date lies with the list's ListUI.

Painting of cells in a JList is handled by a delegate called a cell renderer, installed on the list as the cellRenderer property. The renderer provides a java.awt.Component that is used like a "rubber stamp" to paint the cells. Each time a cell needs to be painted, the list's ListUI asks the cell renderer for the component, moves it into place, and has it paint the contents of the cell by way of its paint method. A default cell renderer, which uses a JLabel component to render, is installed by the lists's ListUI. You can substitute your own renderer using code like this:

  // Display an icon and a string for each object in the list.

 class MyCellRenderer extends JLabel implements ListCellRenderer {
     final static ImageIcon longIcon = new ImageIcon("long.gif");
     final static ImageIcon shortIcon = new ImageIcon("short.gif");

     // This is the only method defined by ListCellRenderer.
     // We just reconfigure the JLabel each time we're called.

     public Component getListCellRendererComponent(
       JList list,              // the list
       Object value,            // value to display
       int index,               // cell index
       boolean isSelected,      // is the cell selected
       boolean cellHasFocus)    // does the cell have focus
     {
         String s = value.toString();
         setText(s);
         setIcon((s.length() > 10) ? longIcon : shortIcon);
         if (isSelected) {
             setBackground(list.getSelectionBackground());
             setForeground(list.getSelectionForeground());
         } else {
             setBackground(list.getBackground());
             setForeground(list.getForeground());
         }
         setEnabled(list.isEnabled());
         setFont(list.getFont());
         setOpaque(true);
         return this;
     }
 }

 myList.setCellRenderer(new MyCellRenderer());
 

Another job for the cell renderer is in helping to determine sizing information for the list. By default, the list's ListUI determines the size of cells by asking the cell renderer for its preferred size for each list item. This can be expensive for large lists of items. To avoid these calculations, you can set a fixedCellWidth and fixedCellHeight on the list, or have these values calculated automatically based on a single prototype value:

 JList bigDataList = new JList(bigData);

 // We don't want the JList implementation to compute the width
 // or height of all of the list cells, so we give it a string
 // that's as big as we'll need for any cell.  It uses this to
 // compute values for the fixedCellWidth and fixedCellHeight
 // properties.

 bigDataList.setPrototypeCellValue("Index 1234567890");
 

 JScrollPane scrollPane = new JScrollPane(myList);

 // Or in two steps:
 JScrollPane scrollPane = new JScrollPane();
 scrollPane.getViewport().setView(myList);
 

 MouseListener mouseListener = new MouseAdapter() {
     public void mouseClicked(MouseEvent e) {
         if (e.getClickCount() == 2) {
             int index = list.locationToIndex(e.getPoint());
             System.out.println("Double clicked on Item " + index);
          }
     }
 };
 list.addMouseListener(mouseListener);
 

Warning: Swing is not thread safe. For more information see Swing's Threading Policy.

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^TM has been added to the java.beans package. Please see XMLEncoder.

See How to Use Lists in The Java Tutorial for further documentation. Also see the article Advanced JList Programming in The Swing Connection.

See Also:

ListModel, AbstractListModel, DefaultListModel, ListSelectionModel, DefaultListSelectionModel, ListCellRenderer, DefaultListCellRenderer

Nested Class Summary
protected  class	JList.AccessibleJList           This class implements accessibility support for the JList class.
static class	JList.DropLocation           A subclass of TransferHandler.DropLocation representing a drop location for a JList.

 

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

 

Field Summary
static int	HORIZONTAL_WRAP           Indicates a "newspaper style" layout with cells flowing horizontally then vertically.
static int	VERTICAL           Indicates a vertical layout of cells, in a single column; the default layout.
static int	VERTICAL_WRAP           Indicates a "newspaper style" layout with cells flowing vertically then horizontally.

 

Fields inherited from class javax.swing.JComponent
accessibleContext, 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
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

 

Constructor Summary
JList()           Constructs a JList with an empty, read-only, model.
JList(ListModel dataModel)           Constructs a JList that displays elements from the specified, non-null, model.
JList(Object[] listData)           Constructs a JList that displays the elements in the specified array.
JList(Vector<?> listData)           Constructs a JList that displays the elements in the specified Vector.

 

Method Summary
void	addListSelectionListener(ListSelectionListener listener)           Adds a listener to the list, to be notified each time a change to the selection occurs; the preferred way of listening for selection state changes.
void	addSelectionInterval(int anchor, int lead)           Sets the selection to be the union of the specified interval with current selection.
void	clearSelection()           Clears the selection; after calling this method, isSelectionEmpty will return true.
protected  ListSelectionModel	createSelectionModel()           Returns an instance of DefaultListSelectionModel; called during construction to initialize the list's selection model property.
void	ensureIndexIsVisible(int index)           Scrolls the list within an enclosing viewport to make the specified cell completely visible.
protected  void	fireSelectionValueChanged(int firstIndex, int lastIndex, boolean isAdjusting)           Notifies ListSelectionListeners added directly to the list of selection changes made to the selection model.
AccessibleContext	getAccessibleContext()           Gets the AccessibleContext associated with this JList.
int	getAnchorSelectionIndex()           Returns the anchor selection index.
Rectangle	getCellBounds(int index0, int index1)           Returns the bounding rectangle, in the list's coordinate system, for the range of cells specified by the two indices.
ListCellRenderer	getCellRenderer()           Returns the object responsible for painting list items.
boolean	getDragEnabled()           Returns whether or not automatic drag handling is enabled.
JList.DropLocation	getDropLocation()           Returns the location that this component should visually indicate as the drop location during a DnD operation over the component, or null if no location is to currently be shown.
DropMode	getDropMode()           Returns the drop mode for this component.
int	getFirstVisibleIndex()           Returns the smallest list index that is currently visible.
int	getFixedCellHeight()           Returns the value of the fixedCellHeight property.
int	getFixedCellWidth()           Returns the value of the fixedCellWidth property.
int	getLastVisibleIndex()           Returns the largest list index that is currently visible.
int	getLayoutOrientation()           Returns the layout orientation property for the list: VERTICAL if the layout is a single column of cells, VERTICAL_WRAP if the layout is "newspaper style" with the content flowing vertically then horizontally, or HORIZONTAL_WRAP if the layout is "newspaper style" with the content flowing horizontally then vertically.
int	getLeadSelectionIndex()           Returns the lead selection index.
ListSelectionListener[]	getListSelectionListeners()           Returns an array of all the ListSelectionListeners added to this JList by way of addListSelectionListener.
int	getMaxSelectionIndex()           Returns the largest selected cell index, or -1 if the selection is empty.
int	getMinSelectionIndex()           Returns the smallest selected cell index, or -1 if the selection is empty.
ListModel	getModel()           Returns the data model that holds the list of items displayed by the JList component.
int	getNextMatch(String prefix, int startIndex, Position.Bias bias)           Returns the next list element whose toString value starts with the given prefix.
Dimension	getPreferredScrollableViewportSize()           Computes the size of viewport needed to display visibleRowCount rows.
Object	getPrototypeCellValue()           Returns the "prototypical" cell value -- a value used to calculate a fixed width and height for cells.
int	getScrollableBlockIncrement(Rectangle visibleRect, int orientation, int direction)           Returns the distance to scroll to expose the next or previous block.
boolean	getScrollableTracksViewportHeight()           Returns true if this JList is displayed in a JViewport and the viewport is taller than the list's preferred height, or if the layout orientation is VERTICAL_WRAP and visibleRowCount <= 0; otherwise returns false.
boolean	getScrollableTracksViewportWidth()           Returns true if this JList is displayed in a JViewport and the viewport is wider than the list's preferred width, or if the layout orientation is HORIZONTAL_WRAP and visibleRowCount <= 0; otherwise returns false.
int	getScrollableUnitIncrement(Rectangle visibleRect, int orientation, int direction)           Returns the distance to scroll to expose the next or previous row (for vertical scrolling) or column (for horizontal scrolling).
int	getSelectedIndex()           Returns the smallest selected cell index; the selection when only a single item is selected in the list.
int[]	getSelectedIndices()           Returns an array of all of the selected indices, in increasing order.
Object	getSelectedValue()           Returns the value for the smallest selected cell index; the selected value when only a single item is selected in the list.
Object[]	getSelectedValues()           Returns an array of all the selected values, in increasing order based on their indices in the list.
Color	getSelectionBackground()           Returns the color used to draw the background of selected items.
Color	getSelectionForeground()           Returns the color used to draw the foreground of selected items.
int	getSelectionMode()           Returns the current selection mode for the list.
ListSelectionModel	getSelectionModel()           Returns the current selection model.
String	getToolTipText(MouseEvent event)           Returns the tooltip text to be used for the given event.
ListUI	getUI()           Returns the ListUI, the look and feel object that renders this component.
String	getUIClassID()           Returns "ListUI", the UIDefaults key used to look up the name of the javax.swing.plaf.ListUI class that defines the look and feel for this component.
boolean	getValueIsAdjusting()           Returns the value of the selection model's isAdjusting property.
int	getVisibleRowCount()           Returns the value of the visibleRowCount property.
Point	indexToLocation(int index)           Returns the origin of the specified item in the list's coordinate system.
boolean	isSelectedIndex(int index)           Returns true if the specified index is selected, else false.
boolean	isSelectionEmpty()           Returns true if nothing is selected, else false.
int	locationToIndex(Point location)           Returns the cell index closest to the given location in the list's coordinate system.
protected  String	paramString()           Returns a String representation of this JList.
void	removeListSelectionListener(ListSelectionListener listener)           Removes a selection listener from the list.
void	removeSelectionInterval(int index0, int index1)           Sets the selection to be the set difference of the specified interval and the current selection.
void	setCellRenderer(ListCellRenderer cellRenderer)           Sets the delegate that is used to paint each cell in the list.
void	setDragEnabled(boolean b)           Turns on or off automatic drag handling.
void	setDropMode(DropMode dropMode)           Sets the drop mode for this component.
void	setFixedCellHeight(int height)           Sets a fixed value to be used for the height of every cell in the list.
void	setFixedCellWidth(int width)           Sets a fixed value to be used for the width of every cell in the list.
void	setLayoutOrientation(int layoutOrientation)           Defines the way list cells are layed out.
void	setListData(Object[] listData)           Constructs a read-only ListModel from an array of objects, and calls setModel with this model.
void	setListData(Vector<?> listData)           Constructs a read-only ListModel from a Vector and calls setModel with this model.
void	setModel(ListModel model)           Sets the model that represents the contents or "value" of the list, notifies property change listeners, and then clears the list's selection.
void	setPrototypeCellValue(Object prototypeCellValue)           Sets the prototypeCellValue property, and then (if the new value is non-null), computes the fixedCellWidth and fixedCellHeight properties by requesting the cell renderer component for the given value (and index 0) from the cell renderer, and using that component's preferred size.
void	setSelectedIndex(int index)           Selects a single cell.
void	setSelectedIndices(int[] indices)           Changes the selection to be the set of indices specified by the given array.
void	setSelectedValue(Object anObject, boolean shouldScroll)           Selects the specified object from the list.
void	setSelectionBackground(Color selectionBackground)           Sets the color used to draw the background of selected items, which cell renderers can use fill selected cells.
void	setSelectionForeground(Color selectionForeground)           Sets the color used to draw the foreground of selected items, which cell renderers can use to render text and graphics.
void	setSelectionInterval(int anchor, int lead)           Selects the specified interval.
void	setSelectionMode(int selectionMode)           Sets the selection mode for the list.
void	setSelectionModel(ListSelectionModel selectionModel)           Sets the selectionModel for the list to a non-null ListSelectionModel implementation.
void	setUI(ListUI ui)           Sets the ListUI, the look and feel object that renders this component.
void	setValueIsAdjusting(boolean b)           Sets the selection model's valueIsAdjusting property.
void	setVisibleRowCount(int visibleRowCount)           Sets the visibleRowCount property, which has different meanings depending on the layout orientation: For a VERTICAL layout orientation, this sets the preferred number of rows to display without requiring scrolling; for other orientations, it affects the wrapping of cells.
void	updateUI()           Resets the ListUI property by setting it to the value provided by the current look and feel.

 

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, getTopLevelAncestor, getTransferHandler, getVerifyInputWhenFocusTarget, getVetoableChangeListeners, getVisibleRect, getWidth, getX, getY, grabFocus, isDoubleBuffered, isLightweightComponent, isManagingFocus, isOpaque, isOptimizedDrawingEnabled, isPaintingForPrint, isPaintingTile, isRequestFocusEnabled, isValidateRoot, paint, paintBorder, paintChildren, paintComponent, paintImmediately, paintImmediately, print, printAll, printBorder, printChildren, printComponent, processComponentKeyEvent, processKeyBinding, processKeyEvent, 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, 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, transferFocusBackward, 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, getPeer, getPropertyChangeListeners, getPropertyChangeListeners, getSize, getToolkit, getTreeLock, gotFocus, handleEvent, hasFocus, hide, 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, resize, resize, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setFocusable, setFocusTraversalKeysEnabled, setIgnoreRepaint, setLocale, setLocation, setLocation, setName, setSize, setSize, show, show, size, toString, transferFocus, transferFocusUpCycle

 

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

 

Field Detail

VERTICAL

public static final int VERTICAL

Indicates a vertical layout of cells, in a single column; the default layout.

Since:

1.4

See Also:

setLayoutOrientation(int), Constant Field Values

VERTICAL_WRAP

public static final int VERTICAL_WRAP

Indicates a "newspaper style" layout with cells flowing vertically then horizontally.

Since:

1.4

See Also:

setLayoutOrientation(int), Constant Field Values

HORIZONTAL_WRAP

public static final int HORIZONTAL_WRAP

Indicates a "newspaper style" layout with cells flowing horizontally then vertically.

Since:

1.4

See Also:

setLayoutOrientation(int), Constant Field Values

JList

public JList(ListModel dataModel)

Constructs a JList that displays elements from the specified, non-null, model. All JList constructors delegate to this one.

This constructor registers the list with the ToolTipManager, allowing for tooltips to be provided by the cell renderers.

Parameters:

dataModel - the model for the list

Throws:

IllegalArgumentException - if the model is null

JList

public JList(Object[] listData)

Constructs a JList that displays the elements in the specified array. This constructor creates a read-only model for the given array, and then delegates to the constructor that takes a ListModel.

Attempts to pass a null value to this method results in undefined behavior and, most likely, exceptions. The created model references the given array directly. Attempts to modify the array after constructing the list results in undefined behavior.

Parameters:

listData - the array of Objects to be loaded into the data model, non-null

JList

public JList(Vector<?> listData)

Constructs a JList that displays the elements in the specified Vector. This constructor creates a read-only model for the given Vector, and then delegates to the constructor that takes a ListModel.

Attempts to pass a null value to this method results in undefined behavior and, most likely, exceptions. The created model references the given Vector directly. Attempts to modify the Vector after constructing the list results in undefined behavior.

Parameters:

listData - the Vector to be loaded into the data model, non-null

JList

public JList()

Constructs a JList with an empty, read-only, model.

getUI

public ListUI getUI()

Returns the ListUI, the look and feel object that renders this component.

Returns:

the ListUI object that renders this component

setUI

public void setUI(ListUI ui)

Sets the ListUI, the look and feel object that renders this component.

Parameters:

ui - the ListUI object

See Also:

UIDefaults.getUI(javax.swing.JComponent)

updateUI

public void updateUI()

Resets the ListUI property by setting it to the value provided by the current look and feel. If the current cell renderer was installed by the developer (rather than the look and feel itself), this also causes the cell renderer and its children to be updated, by calling SwingUtilities.updateComponentTreeUI on it.

Overrides:

updateUI in class JComponent

See Also:

UIManager.getUI(javax.swing.JComponent), SwingUtilities.updateComponentTreeUI(java.awt.Component)

getUIClassID

public String getUIClassID()

Returns "ListUI", the UIDefaults key used to look up the name of the javax.swing.plaf.ListUI class that defines the look and feel for this component.

Overrides:

getUIClassID in class JComponent

Returns:

the string "ListUI"

See Also:

JComponent.getUIClassID(), UIDefaults.getUI(javax.swing.JComponent)

getPrototypeCellValue

public Object getPrototypeCellValue()

Returns the "prototypical" cell value -- a value used to calculate a fixed width and height for cells. This can be null if there is no such value.

Returns:

the value of the prototypeCellValue property

See Also:

setPrototypeCellValue(java.lang.Object)

setPrototypeCellValue

public void setPrototypeCellValue(Object prototypeCellValue)

Sets the prototypeCellValue property, and then (if the new value is non-null), computes the fixedCellWidth and fixedCellHeight properties by requesting the cell renderer component for the given value (and index 0) from the cell renderer, and using that component's preferred size.

This method is useful when the list is too long to allow the ListUI to compute the width/height of each cell, and there is a single cell value that is known to occupy as much space as any of the others, a so-called prototype.

While all three of the prototypeCellValue, fixedCellHeight, and fixedCellWidth properties may be modified by this method, PropertyChangeEvent notifications are only sent when the prototypeCellValue property changes.

To see an example which sets this property, see the class description above.

The default value of this property is null.

This is a JavaBeans bound property.

Parameters:

prototypeCellValue - the value on which to base fixedCellWidth and fixedCellHeight

See Also:

getPrototypeCellValue(), setFixedCellWidth(int), setFixedCellHeight(int), Container.addPropertyChangeListener(java.beans.PropertyChangeListener)

getFixedCellWidth

public int getFixedCellWidth()

Returns the value of the fixedCellWidth property.

Returns:

the fixed cell width

See Also:

setFixedCellWidth(int)

setFixedCellWidth

public void setFixedCellWidth(int width)

Sets a fixed value to be used for the width of every cell in the list. If width is -1, cell widths are computed in the ListUI by applying getPreferredSize to the cell renderer component for each list element.

The default value of this property is -1.

This is a JavaBeans bound property.

Parameters:

width - the width to be used for all cells in the list

See Also:

setPrototypeCellValue(java.lang.Object), setFixedCellWidth(int), Container.addPropertyChangeListener(java.beans.PropertyChangeListener)

getFixedCellHeight

public int getFixedCellHeight()

Returns the value of the fixedCellHeight property.

Returns:

the fixed cell height

See Also:

setFixedCellHeight(int)

setFixedCellHeight

public void setFixedCellHeight(int height)

Sets a fixed value to be used for the height of every cell in the list. If height is -1, cell heights are computed in the ListUI by applying getPreferredSize to the cell renderer component for each list element.

The default value of this property is -1.

This is a JavaBeans bound property.

Parameters:

height - the height to be used for for all cells in the list

See Also:

setPrototypeCellValue(java.lang.Object), setFixedCellWidth(int), Container.addPropertyChangeListener(java.beans.PropertyChangeListener)

getCellRenderer

public ListCellRenderer getCellRenderer()

Returns the object responsible for painting list items.

Returns:

the value of the cellRenderer property

See Also:

setCellRenderer(javax.swing.ListCellRenderer)

setCellRenderer

public void setCellRenderer(ListCellRenderer cellRenderer)

Sets the delegate that is used to paint each cell in the list. The job of a cell renderer is discussed in detail in the class level documentation.

If the prototypeCellValue property is non-null, setting the cell renderer also causes the fixedCellWidth and fixedCellHeight properties to be re-calculated. Only one PropertyChangeEvent is generated however - for the cellRenderer property.

The default value of this property is provided by the ListUI delegate, i.e. by the look and feel implementation.

This is a JavaBeans bound property.

Parameters:

cellRenderer - the ListCellRenderer that paints list cells

See Also:

getCellRenderer()

getSelectionForeground

public Color getSelectionForeground()

Returns the color used to draw the foreground of selected items. DefaultListCellRenderer uses this color to draw the foreground of items in the selected state, as do the renderers installed by most ListUI implementations.

Returns:

the color to draw the foreground of selected items

See Also:

setSelectionForeground(java.awt.Color), DefaultListCellRenderer

setSelectionForeground

public void setSelectionForeground(Color selectionForeground)

Sets the color used to draw the foreground of selected items, which cell renderers can use to render text and graphics. DefaultListCellRenderer uses this color to draw the foreground of items in the selected state, as do the renderers installed by most ListUI implementations.

The default value of this property is defined by the look and feel implementation.

This is a JavaBeans bound property.

Parameters:

selectionForeground - the Color to use in the foreground for selected list items

See Also:

getSelectionForeground(), setSelectionBackground(java.awt.Color), JComponent.setForeground(java.awt.Color), JComponent.setBackground(java.awt.Color), JComponent.setFont(java.awt.Font), DefaultListCellRenderer

getSelectionBackground

public Color getSelectionBackground()

Returns the color used to draw the background of selected items. DefaultListCellRenderer uses this color to draw the background of items in the selected state, as do the renderers installed by most ListUI implementations.

Returns:

the color to draw the background of selected items

See Also:

setSelectionBackground(java.awt.Color), DefaultListCellRenderer

setSelectionBackground

public void setSelectionBackground(Color selectionBackground)

Sets the color used to draw the background of selected items, which cell renderers can use fill selected cells. DefaultListCellRenderer uses this color to fill the background of items in the selected state, as do the renderers installed by most ListUI implementations.

The default value of this property is defined by the look and feel implementation.

This is a JavaBeans bound property.

Parameters:

selectionBackground - the Color to use for the background of selected cells

See Also:

getSelectionBackground(), setSelectionForeground(java.awt.Color), JComponent.setForeground(java.awt.Color), JComponent.setBackground(java.awt.Color), JComponent.setFont(java.awt.Font), DefaultListCellRenderer

getVisibleRowCount

public int getVisibleRowCount()

Returns the value of the visibleRowCount property. See the documentation for setVisibleRowCount(int) for details on how to interpret this value.

Returns:

the value of the visibleRowCount property.

See Also:

setVisibleRowCount(int)

setVisibleRowCount

public void setVisibleRowCount(int visibleRowCount)

Sets the visibleRowCount property, which has different meanings depending on the layout orientation: For a VERTICAL layout orientation, this sets the preferred number of rows to display without requiring scrolling; for other orientations, it affects the wrapping of cells.

In VERTICAL orientation:
Setting this property affects the return value of the getPreferredScrollableViewportSize() method, which is used to calculate the preferred size of an enclosing viewport. See that method's documentation for more details.

In HORIZONTAL_WRAP and VERTICAL_WRAP orientations:
This affects how cells are wrapped. See the documentation of setLayoutOrientation(int) for more details.

The default value of this property is 8.

Calling this method with a negative value results in the property being set to 0.

This is a JavaBeans bound property.

Parameters:

visibleRowCount - an integer specifying the preferred number of rows to display without requiring scrolling

See Also:

getVisibleRowCount(), getPreferredScrollableViewportSize(), setLayoutOrientation(int), JComponent.getVisibleRect(), JViewport

getLayoutOrientation

public int getLayoutOrientation()

Returns the layout orientation property for the list: VERTICAL if the layout is a single column of cells, VERTICAL_WRAP if the layout is "newspaper style" with the content flowing vertically then horizontally, or HORIZONTAL_WRAP if the layout is "newspaper style" with the content flowing horizontally then vertically.

Returns:

the value of the layoutOrientation property

Since:

1.4

See Also:

setLayoutOrientation(int)

setLayoutOrientation

public void setLayoutOrientation(int layoutOrientation)

Defines the way list cells are layed out. Consider a JList with five cells. Cells can be layed out in one of the following ways:

 VERTICAL:          0
                    1
                    2
                    3
                    4

 HORIZONTAL_WRAP:   0  1  2
                    3  4

 VERTICAL_WRAP:     0  3
                    1  4
                    2
 

A description of these layouts follows:

Value	Description
VERTICAL	Cells are layed out vertically in a single column.
HORIZONTAL_WRAP	Cells are layed out horizontally, wrapping to a new row as necessary. If the visibleRowCount property is less than or equal to zero, wrapping is determined by the width of the list; otherwise wrapping is done in such a way as to ensure visibleRowCount rows in the list.
VERTICAL_WRAP	Cells are layed out vertically, wrapping to a new column as necessary. If the visibleRowCount property is less than or equal to zero, wrapping is determined by the height of the list; otherwise wrapping is done at visibleRowCount rows.

The default value of this property is VERTICAL.

Parameters:

layoutOrientation - the new layout orientation, one of: VERTICAL, HORIZONTAL_WRAP or VERTICAL_WRAP

Throws:

IllegalArgumentException - if layoutOrientation isn't one of the allowable values

Since:

1.4

See Also:

getLayoutOrientation(), setVisibleRowCount(int), getScrollableTracksViewportHeight(), getScrollableTracksViewportWidth()

getFirstVisibleIndex

public int getFirstVisibleIndex()

Returns the smallest list index that is currently visible. In a left-to-right componentOrientation, the first visible cell is found closest to the list's upper-left corner. In right-to-left orientation, it is found closest to the upper-right corner. If nothing is visible or the list is empty, -1 is returned. Note that the returned cell may only be partially visible.

Returns:

the index of the first visible cell

See Also:

getLastVisibleIndex(), JComponent.getVisibleRect()

getLastVisibleIndex

public int getLastVisibleIndex()

Returns the largest list index that is currently visible. If nothing is visible or the list is empty, -1 is returned. Note that the returned cell may only be partially visible.

Returns:

the index of the last visible cell

See Also:

getFirstVisibleIndex(), JComponent.getVisibleRect()

ensureIndexIsVisible

public void ensureIndexIsVisible(int index)

Scrolls the list within an enclosing viewport to make the specified cell completely visible. This calls scrollRectToVisible with the bounds of the specified cell. For this method to work, the JList must be within a JViewport.

If the given index is outside the list's range of cells, this method results in nothing.

Parameters:

index - the index of the cell to make visible

See Also:

JComponent.scrollRectToVisible(java.awt.Rectangle), JComponent.getVisibleRect()

setDragEnabled

public void setDragEnabled(boolean b)

Turns on or off automatic drag handling. In order to enable automatic drag handling, this property should be set to true, and the list's TransferHandler needs to be non-null. The default value of the dragEnabled property is false.

The job of honoring this property, and recognizing a user drag gesture, lies with the look and feel implementation, and in particular, the list's ListUI. When automatic drag handling is enabled, most look and feels (including those that subclass BasicLookAndFeel) begin a drag and drop operation whenever the user presses the mouse button over an item and then moves the mouse a few pixels. Setting this property to true can therefore have a subtle effect on how selections behave.

If a look and feel is used that ignores this property, you can still begin a drag and drop operation by calling exportAsDrag on the list's TransferHandler.

Parameters:

b - whether or not to enable automatic drag handling

Throws:

HeadlessException