Java Reference
In-Depth Information
Instead of returning the actual Object , its index (as computed by the order of
calls to addItem ) can be returned by calling getSelectedIndex . The first item
added has index 0, and so on. This can be useful because if an array stores
information corresponding to each of the choices, getSelectedIndex can be
used to index this array. The setSelectedIndex method is used to specify a
default selection.
JList
The JList component allows the selection from a scrolling list of Object s. In
Figure B.1, the choice of colors is presented as a JList . The JList differs from
the JComboBox in three fundamental ways:
The JList compo-
nent allows the
selection from a
scrolling list of
Object s. It can be
set up to allow for
either one selected
item or multiple
selected items.
1.
The JList can be set up to allow either one selected item or
multiple selected items (the default is multiple selection).
2.
The JList allows the user to see more than one choice at a time.
3.
The JList will take up more screen real estate than the Choice .
The basic JList methods are
JList( );
JList( Object [ ] items );
void setListData( Object [ ] items );
int getSelectedIndex( );
int [ ] getSelectedIndices( );
Object getSelectedValue( );
Object [ ] getSelectedValues( );
void setSelectedIndex( int index );
void setSelectedValue( Object value );
void setSelectionMode( int mode );
A JList is constructed with either no parameters or an array of items
(there are other constructors that are more sophisticated). Most of the listed
methods have the same behavior (with possibly different names) as the corre-
sponding methods in JComboxBox . getSelectedValue returns null if no items are
selected. getSelectedValues is used to handle multiple selection; it returns an
array of Object s (possibly length 0) corresponding to the selected items. As
with the JComboxBox , indices instead of Object s can be obtained by other public
methods.
setSelectionMode is used to allow only single-item selection. The boiler-
plate code is
lst.setSelectionMode( ListSelectionModel.SINGLE_SELECTION );
 
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