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Java™ Platform Standard Ed. 6 |
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java.lang.Object java.util.EventObject java.awt.AWTEvent java.awt.event.ComponentEvent java.awt.event.FocusEvent
public class FocusEvent
A low-level event which indicates that a Component has gained or lost the
input focus. This low-level event is generated by a Component (such as a
TextField). 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 events: permanent and temporary. Permanent focus change events occur when focus is directly moved from one Component to another, such as through a call to requestFocus() or as the user uses the TAB key to traverse Components. Temporary focus change events occur when focus is temporarily 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 level may be distinguished in the event using the isTemporary() method.
FocusAdapter
,
FocusListener
,
Tutorial: Writing a Focus Listener,
Serialized FormField Summary | |
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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 is now the focus owner. |
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 is no longer the focus owner. |
Fields inherited from class java.awt.event.ComponentEvent |
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COMPONENT_FIRST, COMPONENT_HIDDEN, COMPONENT_LAST, COMPONENT_MOVED, COMPONENT_RESIZED, COMPONENT_SHOWN |
Fields inherited from class java.util.EventObject |
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source |
Constructor Summary | |
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FocusEvent(Component source,
int id)
Constructs a FocusEvent object and identifies it
as a permanent change in focus. |
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FocusEvent(Component source,
int id,
boolean temporary)
Constructs a FocusEvent object and identifies
whether or not the change is temporary. |
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FocusEvent(Component source,
int id,
boolean temporary,
Component opposite)
Constructs a FocusEvent object with the
specified temporary state and opposite Component . |
Method Summary | |
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Component |
getOppositeComponent()
Returns the other Component involved in this focus change. |
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 |
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getComponent |
Methods inherited from class java.awt.AWTEvent |
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consume, getID, isConsumed, setSource, toString |
Methods inherited from class java.util.EventObject |
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getSource |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Field Detail |
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public static final int FOCUS_FIRST
public static final int FOCUS_LAST
public static final int FOCUS_GAINED
public static final int FOCUS_LOST
Constructor Detail |
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public FocusEvent(Component source, int id, boolean temporary, Component opposite)
FocusEvent
object with the
specified temporary state and opposite Component
.
The opposite Component
is the other
Component
involved in this focus change.
For a FOCUS_GAINED
event, this is the
Component
that lost focus. For a
FOCUS_LOST
event, this is the Component
that gained focus. If this focus change occurs with a native
application, with a Java application in a different VM,
or with no other Component
, then the opposite
Component
is null
.
Note that passing in an invalid id
results in
unspecified behavior. This method throws an
IllegalArgumentException
if source
is null
.
source
- the Component
that originated the eventid
- FOCUS_GAINED
or FOCUS_LOST
temporary
- true
if the focus change is temporary;
false
otherwiseopposite
- the other Component involved in the focus change,
or null
IllegalArgumentException
- if source
is nullpublic FocusEvent(Component source, int id, boolean temporary)
FocusEvent
object and identifies
whether or not the change is temporary.
Note that passing in an invalid id
results in
unspecified behavior. This method throws an
IllegalArgumentException
if source
is null
.
source
- the Component
that originated the eventid
- an integer indicating the type of eventtemporary
- true
if the focus change is temporary;
false
otherwise
IllegalArgumentException
- if source
is nullpublic FocusEvent(Component source, int id)
FocusEvent
object and identifies it
as a permanent change in focus.
Note that passing in an invalid id
results in
unspecified behavior. This method throws an
IllegalArgumentException
if source
is null
.
source
- the Component
that originated the eventid
- an integer indicating the type of event
IllegalArgumentException
- if source
is nullMethod Detail |
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public boolean isTemporary()
true
if the focus change is temporary;
false
otherwisepublic Component getOppositeComponent()
public String paramString()
paramString
in class ComponentEvent
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Java™ Platform Standard Ed. 6 |
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