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Item events are fired by components that implement theItemSelectableinterface. Generally,
ItemSelectablecomponents 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); ... } else { label.setVisible(false); } }
Because
ItemListenerhas 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 Stringcontaining the text on the selected item.ItemSelectable getItemSelectable()Returns the component that fired the item event. You can use this instead of the getSourcemethod.int getStateChange()Returns the new state of the item. The ItemEventclass defines two states:SELECTEDandDESELECTED.
The following table lists some examples that use item listeners.
Example Where Described Notes ComponentEventDemoThis section and How to Write a Component Listener Listens for item events on a check box, which determines whether a lable is visible. CheckBoxDemoHow to Use Check Boxes Four check boxes share one item listener, which uses getItemSelectedto determine which check box fired the event.MenuDemoHow to Use Menus Listens for item events on a check box menu item. MenuDemoHow to Use Scroll Panes Listens for item events on a toggle button.
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