Java Reference
In-Depth Information
JFrame
's content pane (an object of class
Container
). In line 45, we then use that reference
to call method
setBackground
, which sets the content pane's background color to an ele-
ment in the
colors
array. The color is selected from the array by using the selected item's
index.
JList
method
getSelectedIndex
returns the selected item's index. As with arrays
and
JComboBox
es,
JList
indexing is zero based.
A
multiple-selection list
enables the user to select many items from a
JList
(see the output
of Fig. 12.26). A
SINGLE_INTERVAL_SELECTION
list allows selecting a contiguous range of
items. To do so, click the first item, then press and hold the
Shift
key while clicking the
last item in the range. A
MULTIPLE_INTERVAL_SELECTION
list (the default) allows continu-
ous range selection as described for a
SINGLE_INTERVAL_SELECTION
list. Such a list also al-
lows miscellaneous items to be selected by pressing and holding the
Ctrl
key while clicking
each item to select. To
deselect
an item, press and hold the
Ctrl
key while clicking the item
a second time.
The application of Figs. 12.25-12.26 uses multiple-selection lists to copy items from
one
JList
to another. One list is a
MULTIPLE_INTERVAL_SELECTION
list and the other is a
SINGLE_INTERVAL_SELECTION
list. When you execute the application, try using the selec-
tion techniques described previously to select items in both lists.
1
// Fig. 12.25: MultipleSelectionFrame.java
2
// JList that allows multiple selections.
3
import
java.awt.FlowLayout;
4
import
java.awt.event.ActionListener;
5
import
java.awt.event.ActionEvent;
6
import
javax.swing.JFrame;
7
import
javax.swing.JList;
8
import
javax.swing.JButton;
9
import
javax.swing.JScrollPane;
10
import
javax.swing.ListSelectionModel;
11
12
public
class
MultipleSelectionFrame
extends
JFrame
13
{
14
private final
JList<String> colorJList;
// list to hold color names
15
private final
JList<String> copyJList;
// list to hold copied names
16
private
JButton copyJButton;
// button to copy selected names
17
private
static final
String[] colorNames = {
"Black"
,
"Blue"
,
"Cyan"
,
18
"Dark Gray"
,
"Gray"
,
"Green"
,
"Light Gray"
,
"Magenta"
,
"Orange"
,
19
"Pink"
,
"Red"
,
"White"
,
"Yellow"
};
20
21
// MultipleSelectionFrame constructor
22
public
MultipleSelectionFrame()
23
{
24
super
(
"Multiple Selection Lists"
);
25
setLayout(
new
FlowLayout());
26
27
colorJList =
new
JList<String>(colorNames);
// list of color names
28
colorJList.setVisibleRowCount(
5
);
// show five rows
Fig. 12.25
|
JList
that allows multiple selections. (Part 1 of 2.)
