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Item events are fired by components that implement theItemSelectable
interface. Generally,
ItemSelectable
components maintain on/off state for one or more items. The Swing components that fire item events include check boxes, check box menu items
, and combo boxes
.
Here is some item-event handling code taken from
ComponentEventDemo.java
:
... //where initialization occurs checkbox.addItemListener(this); ... public void itemStateChanged(ItemEvent e) { if (e.getStateChange() == ItemEvent.SELECTED) { label.setVisible(true); label.revalidate(); label.repaint(); } else { label.setVisible(false); } }
TheItemListener
interface has just one method, so it has no corresponding adapter class. Here's the method:
The
void itemStateChanged(ItemEvent)
- Called just after a state change in the listened-to component.
itemStateChanged
method hod has a single parameter: anItemEvent
object. The
ItemEvent
class defines the following handy methods:
Object getItem()
- Returns the component-specific object associated with the item whose state changed. Often this is a
String
containing the text on the selected item.ItemSelectable getItemSelectable()
- Returns the component that fired the item event. You can use this instead of the
getSource
method.int getStateChange()
- Returns the new state of the item. The
ItemEvent
class defines two states:SELECTED
andDESELECTED
.
The following table lists some of examples that use item listeners.
Example Where Described Notes ComponentEventDemo
This section and How to Write a Component Listener Listens for item events on a check box, which determines whether a lable is visible. CheckBoxDemo
Getting Started Four check boxes share one item listener, which uses getItemSelected
to determine which check box fired the event.MenuDemo
How to Use Menus Listens for item events on a check box menu item.
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