javax.swing
Class JList

java.lang.Object
  |
  +--java.awt.Component
        |
        +--java.awt.Container
              |
              +--javax.swing.JComponent
                    |
                    +--javax.swing.JList
All Implemented Interfaces:
Accessible, ImageObserver, MenuContainer, Scrollable, Serializable
public class JList
extends JComponent
implements Scrollable, Accessible

A component that allows the user to select one or more objects from a list. A separate model, ListModel, represents the contents of the list. It's easy to display an array or vector of objects, using a JList constructor that builds a ListModel instance for you: 

 // Create a JList that displays the strings in data[]

 String[] data = {"one", "two", "three", "four"};
 JList dataList = new JList(data);
 
 // The value of the JList model property is an object that provides
 // a read-only view of the data.  It was constructed automatically.

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

 // Create a JList that displays the superclass of JList.class.
 // We store the superclasses in a java.util.Vector.

 Vector superClasses = new Vector();
 Class rootClass = javax.swing.JList.class;
 for(Class cls = rootClass; cls != null; cls = cls.getSuperclass()) {
     superClasses.addElement(cls);
 }
 JList classList = new JList(superClasses);

JList doesn't support scrolling directly. To create a scrolling list you make the JList the viewport view of a JScrollPane. For example: 

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

By default the JList selection model allows any combination of items to be selected at a time, using the constant MULTIPLE_INTERVAL_SELECTION. The selection state is actually managed by a separate delegate object, an instance of ListSelectionModel. However JList provides convenient properties for managing the selection. 

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

 dataList.setSelectedIndex(1);  // select "two"
 dataList.getSelectedValue();   // returns "two"

The contents of a JList can be dynamic, in other words, the list elements can change value and the size of the list can change after the JList has been created. The JList observes changes in its model with a swing.event.ListDataListener implementation. A correct implementation of ListModel notifies it's listeners each time a change occurs. The changes are characterized by a swing.event.ListDataEvent, which identifies the range of list indices that have been modified, added, or removed. Simple dynamic-content JList applications can use the DefaultListModel class to store list elements. This class implements the ListModel interface and provides the java.util.Vector API as well. Applications that need to provide custom ListModel implementations can subclass AbstractListModel, which provides basic ListDataListener support. For example: 

 // 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; }
 };

 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");

JList uses a java.awt.Component, provided by a delegate called the cellRendererer, to paint the visible cells in the list. The cell renderer component is used like a "rubber stamp" to paint each visible row. Each time the JList needs to paint a cell it asks the cell renderer for the component, moves it into place using setBounds() and then draws it by calling its paint method. The default cell renderer uses a JLabel component to render the string value of each component. You can substitute your own cell 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,
       Object value,            // value to display
       int index,               // cell index
       boolean isSelected,      // is the cell selected
       boolean cellHasFocus)    // the list and the cell have the 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;
     }
 }

 String[] data = {"one", "two", "three", "four"};
 JList dataList = new JList(data);
 dataList.setCellRenderer(new MyCellRenderer());

JList doesn't provide any special support for handling double or triple (or N) mouse clicks however it's easy to handle them using a MouseListener. Use the JList method locationToIndex() to determine what cell was clicked. For example: 

 final JList list = new JList(dataModel);
 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);
Note that in this example the dataList is final because it's referred to by the anonymous MouseListener class.

For the keyboard keys used by this component in the standard look and feel (L&F) renditions, see the JList key assignments.

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 JavaBeansTM 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

 

Nested Class Summary

protected  class JList.AccessibleJList
    This class implements accessibility support for the JList class.
 
Nested classes inherited from class javax.swing.JComponent
 
Nested classes inherited from class java.awt.Container
 
Nested classes inherited from class java.awt.Component
Component.BltBufferStrategy, Component.FlipBufferStrategy
 

 

Field Summary

static int HORIZONTAL_WRAP
    Indicates "newspaper style" with the cells flowing horizontally then vertically.
static int VERTICAL
    Indicates the default layout: one column of cells.
static int VERTICAL_WRAP
    Indicates "newspaper style" layout with the 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 model.
JList(ListModel dataModel)
    Constructs a JList that displays the elements in 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 that's notified each time a change to the selection occurs.
 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.
 void ensureIndexIsVisible(int index)
    Scrolls the viewport to make the specified cell completely visible.
protected  void fireSelectionValueChanged(int firstIndex, int lastIndex, boolean isAdjusting)
    Notifies JList ListSelectionListeners that the selection model has changed.
 AccessibleContext getAccessibleContext()
    Gets the AccessibleContext associated with this JList.
 int getAnchorSelectionIndex()
    Returns the first index argument from the most recent addSelectionModel or setSelectionInterval call.
 Rectangle getCellBounds(int index0, int index1)
    Returns the bounds of the specified range of items in JList coordinates.
 ListCellRenderer getCellRenderer()
    Returns the object that renders the list items.
 boolean getDragEnabled()
    Gets the dragEnabled property.
 int getFirstVisibleIndex()
    Returns the index of the first visible cell.
 int getFixedCellHeight()
    Returns the fixed cell height value -- the value specified by setting the fixedCellHeight property, rather than that calculated from the list elements.
 int getFixedCellWidth()
    Returns the fixed cell width value -- the value specified by setting the fixedCellWidth property, rather than that calculated from the list elements.
 int getLastVisibleIndex()
    Returns the index of the last visible cell.
 int getLayoutOrientation()
    Returns JList.VERTICAL if the layout is a single column of cells, or JList.VERTICAL_WRAP if the layout is "newspaper style" with the content flowing vertically then horizontally or JList.HORIZONTAL_WRAP if the layout is "newspaper style" with the content flowing horizontally then vertically.
 int getLeadSelectionIndex()
    Returns the second index argument from the most recent addSelectionInterval or setSelectionInterval call.
 ListSelectionListener[] getListSelectionListeners()
    Returns an array of all the ListSelectionListeners added to this JList with addListSelectionListener().
 int getMaxSelectionIndex()
    Returns the largest selected cell index.
 int getMinSelectionIndex()
    Returns the smallest selected cell index.
 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 that starts with a prefix.
 Dimension getPreferredScrollableViewportSize()
    Computes the size of the viewport needed to display visibleRowCount rows.
 Object getPrototypeCellValue()
    Returns the cell width of the "prototypical cell" -- a cell used for the calculation of cell widths, because it has the same value as all other list items.
 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 JList's preferred height, or if the layout orientation is VERTICAL_WRAP and the number of visible rows is <= 0; otherwise returns false.
 boolean getScrollableTracksViewportWidth()
    Returns true if this JList is displayed in a JViewport and the viewport is wider than JList's preferred width; or if the layout orientation is HORIZONTAL_WRAP and the visible row count is <= 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 character (for horizontal scrolling).
 int getSelectedIndex()
    Returns the first selected index; returns -1 if there is no selected item.
 int[] getSelectedIndices()
    Returns an array of all of the selected indices in increasing order.
 Object getSelectedValue()
    Returns the first selected value, or null if the selection is empty.
 Object[] getSelectedValues()
    Returns an array of the values for the selected cells.
 Color getSelectionBackground()
    Returns the background color for selected cells.
 Color getSelectionForeground()
    Returns the selection foreground color.
 int getSelectionMode()
    Returns whether single-item or multiple-item selections are allowed.
 ListSelectionModel getSelectionModel()
    Returns the value of the current selection model.
 String getToolTipText(MouseEvent event)
    Overrides JComponent's getToolTipText method in order to allow the renderer's tips to be used if it has text set.
 ListUI getUI()
    Returns the look and feel (L&F) object that renders this component.
 String getUIClassID()
    Returns the suffix used to construct the name of the look and feel (L&F) class used to render this component.
 boolean getValueIsAdjusting()
    Returns the value of the data model's isAdjusting property.
 int getVisibleRowCount()
    Returns the preferred number of visible rows.
 Point indexToLocation(int index)
    Returns the origin of the specified item in JList coordinates.
 boolean isSelectedIndex(int index)
    Returns true if the specified index is selected.
 boolean isSelectionEmpty()
    Returns true if nothing is selected.
 int locationToIndex(Point location)
    Convert a point in JList coordinates to the closest index of the cell at that location.
protected  String paramString()
    Returns a string representation of this JList.
 void removeListSelectionListener(ListSelectionListener listener)
    Removes a listener from the list that's notified each time a change to the selection occurs.
 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's used to paint each cell in the list.
 void setDragEnabled(boolean b)
    Sets the dragEnabled property, which must be true to enable automatic drag handling (the first part of drag and drop) on this component.
 void setFixedCellHeight(int height)
    Sets the height of every cell in the list.
 void setFixedCellWidth(int width)
    Sets 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 ListModel from an array of objects and then applies setModel to it.
 void setListData(Vector listData)
    Constructs a ListModel from a Vector and then applies setModel to it.
 void setModel(ListModel model)
    Sets the model that represents the contents or "value" of the list and clears the list selection after notifying PropertyChangeListeners.
 void setPrototypeCellValue(Object prototypeCellValue)
    Computes the fixedCellWidth and fixedCellHeight properties by configuring the cellRenderer to index equals zero for the specified value and then computing the renderer component's preferred size.
 void setSelectedIndex(int index)
    Selects a single cell.
 void setSelectedIndices(int[] indices)
    Selects a set of cells.
 void setSelectedValue(Object anObject, boolean shouldScroll)
    Selects the specified object from the list.
 void setSelectionBackground(Color selectionBackground)
    Sets the background color for selected cells.
 void setSelectionForeground(Color selectionForeground)
    Sets the foreground color for selected cells.
 void setSelectionInterval(int anchor, int lead)
    Selects the specified interval.
 void setSelectionMode(int selectionMode)
    Determines whether single-item or multiple-item selections are allowed.
 void setSelectionModel(ListSelectionModel selectionModel)
    Sets the selectionModel for the list to a non-null ListSelectionModel implementation.
 void setUI(ListUI ui)
    Sets the look and feel (L&F) object that renders this component.
 void setValueIsAdjusting(boolean b)
    Sets the data model's isAdjusting property to true, so that a single event will be generated when all of the selection events have finished (for example, when the mouse is being dragged over the list in selection mode).
 void setVisibleRowCount(int visibleRowCount)
    Sets the preferred number of rows in the list that can be displayed without a scrollbar, as determined by the nearest JViewport ancestor, if any.
 void updateUI()
    Resets the UI property with the value from the current look and feel.
 
Methods inherited from class javax.swing.JComponent
addAncestorListener, addNotify, addPropertyChangeListener, addPropertyChangeListener, addVetoableChangeListener, computeVisibleRect, contains, createToolTip, disable, enable, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, fireVetoableChange, getActionForKeyStroke, getActionMap, getAlignmentX, getAlignmentY, getAncestorListeners, getAutoscrolls, getBorder, getBounds, getClientProperty, getComponentGraphics, getConditionForKeyStroke, getDebugGraphicsOptions, getDefaultLocale, getGraphics, getHeight, getInputMap, getInputMap, getInputVerifier, getInsets, getInsets, getListeners, getLocation, getMaximumSize, getMinimumSize, getNextFocusableComponent, getPreferredSize, getPropertyChangeListeners, getPropertyChangeListeners, getRegisteredKeyStrokes, getRootPane, getSize, getToolTipLocation, getToolTipText, getTopLevelAncestor, getTransferHandler, getVerifyInputWhenFocusTarget, getVetoableChangeListeners, getVisibleRect, getWidth, getX, getY, grabFocus, isDoubleBuffered, isLightweightComponent, isManagingFocus, isMaximumSizeSet, isMinimumSizeSet, isOpaque, isOptimizedDrawingEnabled, isPaintingTile, isPreferredSizeSet, isRequestFocusEnabled, isValidateRoot, paint, paintBorder, paintChildren, paintComponent, paintImmediately, paintImmediately, print, printAll, printBorder, printChildren, printComponent, processComponentKeyEvent, processKeyBinding, processKeyEvent, processMouseMotionEvent, putClientProperty, registerKeyboardAction, registerKeyboardAction, removeAncestorListener, removeNotify, removePropertyChangeListener, removePropertyChangeListener, removeVetoableChangeListener, repaint, repaint, requestDefaultFocus, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, resetKeyboardActions, reshape, revalidate, scrollRectToVisible, setActionMap, setAlignmentX, setAlignmentY, setAutoscrolls, setBackground, setBorder, setDebugGraphicsOptions,