Prentice.Hall.Introduction.to.Java.Programming,.Brief.Version.9th.(2014).[sharethefiles.com]

648 Chapter 17 GUI Components
javax.swing.JComponent
javax.swing.JComboBox
+JComboBox()
+JComboBox(items: Object[])
+addItem(item: Object): void
+getItemAt(index: int): Object
+getItemCount(): int
+getSelectedIndex(): int
+setSelectedIndex(index: int): void
+getSelectedItem(): Object
+setSelectedItem(item: Object): void
+removeItem(anObject: Object): void
+removeItemAt(anIndex: int): void
+removeAllItems(): void
+addActionEvent(listener:
ActionListener): void
+addItemListener(listener:
ItemListener) : void
Creates a default empty combo box.
Creates a combo box that contains the elements in the specified array.
Adds an item to the combo box.
Returns the item at the specified index.
Returns the number of items in the combo box.
Returns the index of the selected item.
Sets the selected index in the combo box.
Returns the selected item.
Sets the selected item in the combo box.
Removes an item from the item list.
Removes the item at the specified index in the combo box.
Removes all the items in the combo box.
Adds an ActionListener for this object.
Adds an ItemListener for this object.
FIGURE 17.5
JComboBox enables you to select an item from a set of items.
Listing 17.4 gives a program that lets users view an image and a description of a country’s
flag by selecting the country from a combo box, as shown in Figure 17.6.
Combo box
DescriptionPanel
FIGURE 17.6 Information about a country, including an image and a description of its flag,
is displayed when the country is selected in the combo box.
Here are the major steps in the program:
1. Create the user interface.
Create a combo box with country names as its selection values. Create a
DescriptionPanel object (the DescriptionPanel class was introduced in the preceding
section). Place the combo box in the north of the frame and the description panel
in the center of the frame.
2. Process the event.
Create a listener to implement the itemStateChanged handler to set the flag title,
image, and text in the description panel for the selected country name.