The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
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Item events are fired by components that implement the
ItemSelectable
interface. Generally, ItemSelectable
components maintain on/off state for one or more items. The Swing components that fire item events include buttons like
check boxes,
check menu items,
toggle buttons etc...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); ... } else { label.setVisible(false); } }
Because ItemListener
has only one method, it has no corresponding adapter class.
Method | Purpose |
---|---|
itemStateChanged(ItemEvent) | Called just after a state change in the listened-to component. |
Method | Purpose |
---|---|
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 and DESELECTED . |
The following table lists some 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 label is visible. |
CheckBoxDemo |
How to Use Check Boxes | 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. |
MenuDemo |
How to Use Scroll Panes | Listens for item events on a toggle button. |