CHOICE CONTROLS

The Choice class is used to create a pop-up list of items from which the user may
choose. Thus, a Choice control is a form of menu. When inactive, a Choice component
takes up only enough space to show the currently selected item. When the user clicks
on it, the whole list of choices pops up, and a new selection can be made. Each item
in the list is a string that appears as a left-justified label in the order it is added to the
Choice object. Choice only defines the default constructor, which creates an empty list.
To add a selection to the list, call add( ). It has this general form:
void add(String name)
Here, name is the name of the item being added. Items are added to the list in the order
in which calls to add( ) occur.
To determine which item is currently selected, you may call either getSelectedItem( )
or getSelectedIndex( ). These methods are shown here:
String getSelectedItem( )
int getSelectedIndex( )
The getSelectedItem( ) method returns a string containing the name of the item.
getSelectedIndex( ) returns the index of the item. The first item is at index 0. By
default, the first item added to the list is selected.
To obtain the number of items in the list, call getItemCount( ). You can set the
currently selected item using the select( ) method with either a zero-based integer
index or a string that will match a name in the list. These methods are shown here:
int getItemCount( )
void select(int index)
void select(String name)
Given an index, you can obtain the name associated with the item at that index by
calling getItem( ), which has this general form:
String getItem(int index)
Here, index specifies the index of the desired item.
Handling Choice Lists
Each time a choice is selected, an item event is generated. This is sent to any listeners
that previously registered an interest in receiving item event notifications from that
component. Each listener implements the ItemListener interface. That interface defines
the itemStateChanged( ) method. An ItemEvent object is supplied as the argument to
this method.

Here is an example that creates two Choice menus. One selects the operating
system. The other selects the browser.
// Demonstrate Choice lists.
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
/*


*/
public class ChoiceDemo extends Applet implements ItemListener {
Choice os, browser;
String msg = "";
public void init() {
os = new Choice();
browser = new Choice();
// add items to os list
os.add("Windows 98/XP");
os.add("Windows NT/2000");
os.add("Solaris");
os.add("MacOS");
// add items to browser list
browser.add("Netscape 3.x");
browser.add("Netscape 4.x");
browser.add("Netscape 5.x");
browser.add("Netscape 6.x");
browser.add("Internet Explorer 4.0");
browser.add("Internet Explorer 5.0");
browser.add("Internet Explorer 6.0");
browser.add("Lynx 2.4");
browser.select("Netscape 4.x");
// add choice lists to window
add(os);

add(browser);
// register to receive item events
os.addItemListener(this);
browser.addItemListener(this);
}
public void itemStateChanged(ItemEvent ie) {
repaint();
}
// Display current selections.
public void paint(Graphics g) {
msg = "Current OS: ";
msg += os.getSelectedItem();
g.drawString(msg, 6, 120);
msg = "Current Browser: ";
msg += browser.getSelectedItem();
g.drawString(msg, 6, 140);
}
}