Class FocusEvent
- All Implemented Interfaces:
Serializable
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.
Every FocusEvent
records its cause - the reason why this event was
generated. The cause is assigned during the focus event creation and may be
retrieved by calling getCause()
.
An unspecified behavior will be caused if the id
parameter
of any particular FocusEvent
instance is not
in the range from FOCUS_FIRST
to FOCUS_LAST
.
- Since:
- 1.1
- See Also:
-
Nested Class Summary
Modifier and TypeClassDescriptionstatic enum
This enum represents the cause of aFocusEvent
- the reason why it occurred. -
Field Summary
Modifier and TypeFieldDescriptionstatic final int
The first number in the range of ids used for focus events.static final int
This event indicates that the Component is now the focus owner.static final int
The last number in the range of ids used for focus events.static final int
This event indicates that the Component is no longer the focus owner.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, 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
ConstructorDescriptionFocusEvent
(Component source, int id) Constructs aFocusEvent
object and identifies it as a permanent change in focus.FocusEvent
(Component source, int id, boolean temporary) Constructs aFocusEvent
object and identifies whether or not the change is temporary.FocusEvent
(Component source, int id, boolean temporary, Component opposite) Constructs aFocusEvent
object with the specified temporary state, oppositeComponent
and theCause.UNKNOWN
cause.FocusEvent
(Component source, int id, boolean temporary, Component opposite, FocusEvent.Cause cause) Constructs aFocusEvent
object with the specified temporary state, oppositeComponent
and the cause. -
Method Summary
Modifier and TypeMethodDescriptionfinal FocusEvent.Cause
getCause()
Returns the event cause.Returns the other Component involved in this focus change.boolean
Identifies the focus change event as temporary or permanent.Returns a parameter string identifying this event.Methods inherited from class java.awt.event.ComponentEvent
getComponent
Methods inherited from class java.util.EventObject
getSource
-
Field Details
-
FOCUS_FIRST
public static final int FOCUS_FIRSTThe first number in the range of ids used for focus events.- See Also:
-
FOCUS_LAST
public static final int FOCUS_LASTThe last number in the range of ids used for focus events.- See Also:
-
FOCUS_GAINED
public static final int FOCUS_GAINEDThis event indicates that the Component is now the focus owner.- See Also:
-
FOCUS_LOST
public static final int FOCUS_LOSTThis event indicates that the Component is no longer the focus owner.- See Also:
-
-
Constructor Details
-
FocusEvent
Constructs aFocusEvent
object with the specified temporary state, oppositeComponent
and theCause.UNKNOWN
cause. The oppositeComponent
is the otherComponent
involved in this focus change. For aFOCUS_GAINED
event, this is theComponent
that lost focus. For aFOCUS_LOST
event, this is theComponent
that gained focus. If this focus change occurs with a native application, with a Java application in a different VM, or with no otherComponent
, then the oppositeComponent
isnull
.This method throws an
IllegalArgumentException
ifsource
isnull
.- Parameters:
source
- TheComponent
that originated the eventid
- An integer indicating the type of event. For information on allowable values, see the class description forFocusEvent
temporary
- Equalstrue
if the focus change is temporary;false
otherwiseopposite
- The other Component involved in the focus change, ornull
- Throws:
IllegalArgumentException
- ifsource
equalsnull
- Since:
- 1.4
- See Also:
-
FocusEvent
public FocusEvent(Component source, int id, boolean temporary, Component opposite, FocusEvent.Cause cause) Constructs aFocusEvent
object with the specified temporary state, oppositeComponent
and the cause. The oppositeComponent
is the otherComponent
involved in this focus change. For aFOCUS_GAINED
event, this is theComponent
that lost focus. For aFOCUS_LOST
event, this is theComponent
that gained focus. If this focus change occurs with a native application, with a Java application in a different VM, or with no otherComponent
, then the oppositeComponent
isnull
.This method throws an
IllegalArgumentException
ifsource
orcause
isnull
.- Parameters:
source
- TheComponent
that originated the eventid
- An integer indicating the type of event. For information on allowable values, see the class description forFocusEvent
temporary
- Equalstrue
if the focus change is temporary;false
otherwiseopposite
- The other Component involved in the focus change, ornull
cause
- The focus event cause.- Throws:
IllegalArgumentException
- ifsource
equalsnull
or ifcause
equalsnull
- Since:
- 9
- See Also:
-
FocusEvent
Constructs aFocusEvent
object and identifies whether or not the change is temporary.This method throws an
IllegalArgumentException
ifsource
isnull
.- Parameters:
source
- TheComponent
that originated the eventid
- An integer indicating the type of event. For information on allowable values, see the class description forFocusEvent
temporary
- Equalstrue
if the focus change is temporary;false
otherwise- Throws:
IllegalArgumentException
- ifsource
equalsnull
- See Also:
-
FocusEvent
Constructs aFocusEvent
object and identifies it as a permanent change in focus.This method throws an
IllegalArgumentException
ifsource
isnull
.- Parameters:
source
- TheComponent
that originated the eventid
- An integer indicating the type of event. For information on allowable values, see the class description forFocusEvent
- Throws:
IllegalArgumentException
- ifsource
equalsnull
- See Also:
-
-
Method Details
-
isTemporary
public boolean isTemporary()Identifies the focus change event as temporary or permanent.- Returns:
true
if the focus change is temporary;false
otherwise
-
getOppositeComponent
Returns 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 context, or with no other Component, then null is returned.- Returns:
- the other Component involved in the focus change, or null
- Since:
- 1.4
-
paramString
Returns a parameter string identifying this event. This method is useful for event-logging and for debugging.- Overrides:
paramString
in classComponentEvent
- Returns:
- a string identifying the event and its attributes
-
getCause
Returns the event cause.- Returns:
- one of
FocusEvent.Cause
values - Since:
- 9
-