Java How to Program Fourth Edition - DCC

Chapter 12 Graphical User Interface Components: Part 1 673
67 application.setDefaultCloseOperation(
68 JFrame.EXIT_ON_CLOSE );
69 }
70
71 } // end class ComboBoxTest
A scrollbar to scroll through
the items in the list.
Fig. Fig. 12.13 12.13 Program that uses a JComboBox to select an icon (part 3 of 3).
Look-and-Feel Observation 12.7
Set the maximum row count for a JComboBox to a number of rows that prevents the list from
expanding outside the bounds of the window or applet in which it is used. This will ensure
that the list displays correctly when it is expanded by the user. 12.7
Lines 34–50 register an instance of an anonymous inner class that implements Item-
Listener as the listener for JComboBox images. When the user makes a selection
from images, method itemStateChanged (line 40–46) sets the Icon for label.
The Icon is selected from array icons by determining the index number of the selected
item in the JComboBox with method getSelectedIndex in line 45. Note that line 43
changes the icon only for a selected item. The reason for the if structure here is that for
each item that is selected from a JComboBox, another item is deselected. Thus, two events
occur for each item selected. We wish to display only the icon for the item the user just
selected.
12.9 JList
scroll arrows scroll box
A list displays a series of items from which the user may select one or more items. Lists are
created with class JList, which inherits from class JComponent. Class JList supports
single-selection lists (i.e., lists that allow only one item to be selected at a time) and
multiple-selection lists (lists that allow any number of items to be selected). In this section,
we discuss single-selection lists.
© Copyright 1992–2002 by Deitel & Associates, Inc. All Rights Reserved. 7/7/01