Spec-Zone .ru
спецификации, руководства, описания, API
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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
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 |
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itemStateChanged(ItemEvent) | Called just after a state change in the listened-to component. |
Method | Purpose |
---|---|
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Returns the component-specific object associated with the item whose state changed. Often this is a String containing the text on the selected item. |
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Returns the component that fired the item event. You can use this instead of the getSource method. |
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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 |
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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 |
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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. |