ItemEvent (Java 2 Platform SE 5.0) - JDK 5 Documentation v1.5.0, Java 2 SDK 英文文档

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Java^TM 2 Platform
Standard Ed. 5.0

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java.awt.event
Class ItemEvent

java.lang.Object
  java.util.EventObject
      java.awt.AWTEvent
          java.awt.event.ItemEvent

All Implemented Interfaces:: Serializable

public class ItemEvent
extends AWTEvent
extends AWTEvent

A semantic event which indicates that an item was selected or deselected. This high-level event is generated by an ItemSelectable object (such as a List) when an item is selected or deselected by the user. The event is passed to every ItemListener object which registered to receive such events using the component's addItemListener method.

The object that implements the ItemListener interface gets this ItemEvent when the event occurs. The listener is spared the details of processing individual mouse movements and mouse clicks, and can instead process a "meaningful" (semantic) event like "item selected" or "item deselected".

Since:: 1.1
See Also:: ItemSelectable, ItemListener, Tutorial: Writing an Item Listener, Reference: The Java Class Libraries (update file), Serialized Form

Field Summary

static int DESELECTED
          This state-change-value indicates that a selected item was deselected.

static int ITEM_FIRST
          The first number in the range of ids used for item events.

static int ITEM_LAST
          The last number in the range of ids used for item events.

static int ITEM_STATE_CHANGED
          This event id indicates that an item's state changed.

static int SELECTED
          This state-change value indicates that an item was selected.

Fields inherited from class java.awt.AWTEvent

ACTION_EVENT_MASK, ADJUSTMENT_EVENT_MASK, COMPONENT_EVENT_MASK, consumed, CONTAINER_EVENT_MASK, FOCUS_EVENT_MASK, HIERARCHY_BOUNDS_EVENT_MASK, HIERARCHY_EVENT_MASK, id, INPUT_METHOD_EVENT_MASK, INVOCATION_EVENT_MASK, ITEM_EVENT_MASK, KEY_EVENT_MASK, MOUSE_EVENT_MASK, MOUSE_MOTION_EVENT_MASK, MOUSE_WHEEL_EVENT_MASK, PAINT_EVENT_MASK, RESERVED_ID_MAX, TEXT_EVENT_MASK, WINDOW_EVENT_MASK, WINDOW_FOCUS_EVENT_MASK, WINDOW_STATE_EVENT_MASK

Fields inherited from class java.util.EventObject

source

Constructor Summary

ItemEvent(ItemSelectable source, int id, Object item, int stateChange)
          Constructs an ItemEvent object.

Method Summary

Object getItem()
          Returns the item affected by the event.

ItemSelectable getItemSelectable()
          Returns the originator of the event.

int getStateChange()
          Returns the type of state change (selected or deselected).

String paramString()
          Returns a parameter string identifying this item event.

Methods inherited from class java.awt.AWTEvent

consume, getID, isConsumed, setSource, toString

Methods inherited from class java.util.EventObject

getSource

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Summary
`static int`	`DESELECTED` This state-change-value indicates that a selected item was deselected.
`static int`	`ITEM_FIRST` The first number in the range of ids used for item events.
`static int`	`ITEM_LAST` The last number in the range of ids used for item events.
`static int`	`ITEM_STATE_CHANGED` This event id indicates that an item's state changed.
`static int`	`SELECTED` This state-change value indicates that an item was selected.

Fields inherited from class java.awt.AWTEvent
`ACTION_EVENT_MASK, ADJUSTMENT_EVENT_MASK, COMPONENT_EVENT_MASK, consumed, CONTAINER_EVENT_MASK, FOCUS_EVENT_MASK, HIERARCHY_BOUNDS_EVENT_MASK, HIERARCHY_EVENT_MASK, id, INPUT_METHOD_EVENT_MASK, INVOCATION_EVENT_MASK, ITEM_EVENT_MASK, KEY_EVENT_MASK, MOUSE_EVENT_MASK, MOUSE_MOTION_EVENT_MASK, MOUSE_WHEEL_EVENT_MASK, PAINT_EVENT_MASK, RESERVED_ID_MAX, TEXT_EVENT_MASK, WINDOW_EVENT_MASK, WINDOW_FOCUS_EVENT_MASK, WINDOW_STATE_EVENT_MASK`

Fields inherited from class java.util.EventObject
`source`

Constructor Summary
`ItemEvent(ItemSelectable source, int id, Object item, int stateChange)` Constructs an `ItemEvent` object.

Method Summary
`Object`	`getItem()` Returns the item affected by the event.
`ItemSelectable`	`getItemSelectable()` Returns the originator of the event.
`int`	`getStateChange()` Returns the type of state change (selected or deselected).
`String`	`paramString()` Returns a parameter string identifying this item event.

Methods inherited from class java.awt.AWTEvent
`consume, getID, isConsumed, setSource, toString`

Methods inherited from class java.util.EventObject
`getSource`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Field Detail

ITEM_FIRST

public static final int ITEM_FIRST

The first number in the range of ids used for item events.

See Also:: Constant Field Values

ITEM_LAST

public static final int ITEM_LAST

The last number in the range of ids used for item events.

See Also:: Constant Field Values

ITEM_STATE_CHANGED

public static final int ITEM_STATE_CHANGED

This event id indicates that an item's state changed.

See Also:: Constant Field Values

SELECTED

public static final int SELECTED

This state-change value indicates that an item was selected.

See Also:: Constant Field Values

DESELECTED

public static final int DESELECTED

This state-change-value indicates that a selected item was deselected.

See Also:: Constant Field Values

Constructor Detail

ItemEvent

public ItemEvent(ItemSelectable source,
                 int id,
                 Object item,
                 int stateChange)

Constructs an ItemEvent object.

Note that passing in an invalid id results in unspecified behavior. This method throws an IllegalArgumentException if source is null.

Parameters:: source - the ItemSelectable object that originated the event; id - an integer that identifies the event type; item - an object -- the item affected by the event; stateChange - an integer that indicates whether the item was selected or deselected
Throws:: IllegalArgumentException - if source is null

Method Detail

getItemSelectable

public ItemSelectable getItemSelectable()

Returns the originator of the event.

Returns:: the ItemSelectable object that originated the event.

getItem

public Object getItem()

Returns the item affected by the event.

Returns:: the item (object) that was affected by the event

getStateChange

public int getStateChange()

Returns the type of state change (selected or deselected).

Returns:: an integer that indicates whether the item was selected or deselected
See Also:: SELECTED, DESELECTED

paramString

public String paramString()

Returns a parameter string identifying this item event. This method is useful for event-logging and for debugging.

Overrides:: paramString in class AWTEvent

Returns:: a string identifying the event and its attributes