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Java(TM) 2 Platform, Standard Edition, v1.2.2 API Specification: Class FocusEvent - JDK 5 Documentation v1.2.2, Java 2 SDK 英文文档

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java.awt.event
Class FocusEvent

java.lang.Object
  |
  +--java.util.EventObject
        |
        +--java.awt.AWTEvent
              |
              +--java.awt.event.ComponentEvent
                    |
                    +--java.awt.event.FocusEvent

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public class FocusEvent

extends ComponentEvent

A low-level event which indicates that a component has gained or lost the keyboard focus. This low-level event is generated by a component (such as a text field). The event is passed to every FocusListener or FocusAdapter object which registered to receive such events using the component's addFocusListener method. (FocusAdapter objects implement the FocusListener interface.) Each such listener object gets this FocusEvent when the event occurs.

There are two levels of focus change events: permanent and temporary. Permanent focus change events occur when focus is directly moved from one component to another, such as through calls to requestFocus() or as the user uses the Tab key to traverse components. Temporary focus change events occur when focus is temporarily gained or lost for a component as the indirect result of another operation, such as window deactivation or a scrollbar drag. In this case, the original focus state will automatically be restored once that operation is finished, or, for the case of window deactivation, when the window is reactivated. Both permanent and temporary focus events are delivered using the FOCUS_GAINED and FOCUS_LOST event ids; the levels may be distinguished in the event using the isTemporary() method.

See Also:

FocusAdapter, FocusListener, Tutorial: Writing a Focus Listener, Reference: The Java Class Libraries (update file), Serialized Form

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Field Summary
static int	FOCUS_FIRST           The first number in the range of ids used for focus events.
static int	FOCUS_GAINED           This event indicates that the component gained the keyboard focus.
static int	FOCUS_LAST           The last number in the range of ids used for focus events.
static int	FOCUS_LOST           This event indicates that the component lost the keyboard focus.

 

Fields inherited from class java.awt.event.ComponentEvent

COMPONENT_FIRST, COMPONENT_HIDDEN, COMPONENT_LAST, COMPONENT_MOVED, COMPONENT_RESIZED, COMPONENT_SHOWN

 

Fields inherited from class java.awt.AWTEvent

ACTION_EVENT_MASK, ADJUSTMENT_EVENT_MASK, COMPONENT_EVENT_MASK, consumed, CONTAINER_EVENT_MASK, FOCUS_EVENT_MASK, id, INPUT_METHOD_EVENT_MASK, ITEM_EVENT_MASK, KEY_EVENT_MASK, MOUSE_EVENT_MASK, MOUSE_MOTION_EVENT_MASK, RESERVED_ID_MAX, TEXT_EVENT_MASK, WINDOW_EVENT_MASK

 

Fields inherited from class java.util.EventObject

source

 

Constructor Summary

FocusEvent(Component source, int id)           Constructs a FocusEvent object and identifies it as a permanent change in focus.

FocusEvent(Component source, int id, boolean temporary)           Constructs a FocusEvent object and identifies whether or not the change is temporary.

 

Method Summary
boolean	isTemporary()           Identifies the focus change event as temporary or permanent.
String	paramString()           Returns a parameter string identifying this event.

 

Methods inherited from class java.awt.event.ComponentEvent

getComponent

 

Methods inherited from class java.awt.AWTEvent

consume, finalize, getID, isConsumed, toString

 

Methods inherited from class java.util.EventObject

getSource

 

Methods inherited from class java.lang.Object

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

 

Field Detail

FOCUS_FIRST

public static final int FOCUS_FIRST

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

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FOCUS_LAST

public static final int FOCUS_LAST

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

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FOCUS_GAINED

public static final int FOCUS_GAINED

This event indicates that the component gained the keyboard focus.

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FOCUS_LOST

public static final int FOCUS_LOST

This event indicates that the component lost the keyboard focus.

Constructor Detail

FocusEvent

public FocusEvent(Component source,
                  int id,
                  boolean temporary)

Constructs a FocusEvent object and identifies whether or not the change is temporary.

Parameters:

source - the Component that originated the event

id - an integer indicating the type of event

temporary - a boolean, true if the focus change is temporary

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FocusEvent

public FocusEvent(Component source,
                  int id)

Constructs a FocusEvent object and identifies it as a permanent change in focus.

Parameters:

source - the Component that originated the event

id - an integer indicating the type of event

Method Detail

isTemporary

public boolean isTemporary()

Identifies the focus change event as temporary or permanent.

Returns:

a boolean value, true if the focus change is temporary

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paramString

public String paramString()

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

Overrides:

paramString in class ComponentEvent

Returns:

a string identifying the event and its attributes

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