Java Reference
In-Depth Information
class
JComponent
.
JComboBox
is a generic class, like the class
ArrayList
(Chapter 7). When
you create a
JComboBox
, you specify the type of the objects that it manages—the
JCombo-
Box
then displays a
String
representation of each object.
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// Fig. 12.21: ComboBoxFrame.java
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// JComboBox that displays a list of image names.
3
import
java.awt.FlowLayout;
4
import
java.awt.event.ItemListener;
5
import
java.awt.event.ItemEvent;
6
import
javax.swing.JFrame;
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import
javax.swing.JLabel;
8
import
javax.swing.JComboBox;
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import
javax.swing.Icon;
10
import
javax.swing.ImageIcon;
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12
public
class
ComboBoxFrame
extends
JFrame
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{
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private final
JComboBox<String> imagesJComboBox;
// holds icon names
15
private final
JLabel label;
// displays selected icon
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private static final
String[] names =
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{
"bug1.gif"
,
"bug2.gif"
,
"travelbug.gif"
,
"buganim.gif"
};
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private final
Icon[] icons = {
20
new
ImageIcon(getClass().getResource(names[
0
])),
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new
ImageIcon(getClass().getResource(names[
1
])),
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new
ImageIcon(getClass().getResource(names[
2
])),
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new
ImageIcon(getClass().getResource(names[
3
]))};
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// ComboBoxFrame constructor adds JComboBox to JFrame
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public
ComboBoxFrame()
27
{
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super
(
"Testing JComboBox")
;
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setLayout(
new
FlowLayout());
// set frame layout
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imagesJComboBox =
new
JComboBox<String>(names);
// set up JComboBox
imagesJComboBox.setMaximumRowCount(
3
);
// display three rows
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33
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imagesJComboBox.addItemListener(
new
ItemListener()
// anonymous inner class
{
// handle JComboBox event
@Override
public
void
itemStateChanged(ItemEvent event)
{
// determine whether item selected
if
(event.getStateChange() ==
ItemEvent.SELECTED
)
label.setIcon(icons[
imagesJComboBox.getSelectedIndex()]);
}
}
// end anonymous inner class
);
// end call to addItemListener
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Fig. 12.21
|
JComboBox
that displays a list of image names. (Part 1 of 2.)
