Class FocusEvent

java.awt.event.FocusEvent

All Implemented Interfaces:: Serializable

public class FocusEvent extends ComponentEvent

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.

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 Type	Class	Description
`static enum`	`FocusEvent.Cause`	This enum represents the cause of a `FocusEvent`- the reason why it occurred.

Field Summary

Modifier and Type	Field	Description
`static final int`	`FOCUS_FIRST`	The first number in the range of ids used for focus events.
`static final int`	`FOCUS_GAINED`	This event indicates that the Component is now the focus owner.
`static final int`	`FOCUS_LAST`	The last number in the range of ids used for focus events.
`static final int`	`FOCUS_LOST`	This event indicates that the Component is no longer the focus owner.

Fields declared in class ComponentEvent

COMPONENT_FIRST, COMPONENT_HIDDEN, COMPONENT_LAST, COMPONENT_MOVED, COMPONENT_RESIZED, COMPONENT_SHOWN

Modifier and Type	Field	Description
`static final int`	`COMPONENT_FIRST`	The first number in the range of ids used for component events.
`static final int`	`COMPONENT_HIDDEN`	This event indicates that the component was rendered invisible.
`static final int`	`COMPONENT_LAST`	The last number in the range of ids used for component events.
`static final int`	`COMPONENT_MOVED`	This event indicates that the component's position changed.
`static final int`	`COMPONENT_RESIZED`	This event indicates that the component's size changed.
`static final int`	`COMPONENT_SHOWN`	This event indicates that the component was made visible.

Fields declared in class 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

Modifier and Type	Field	Description
`static final long`	`ACTION_EVENT_MASK`	The event mask for selecting action events.
`static final long`	`ADJUSTMENT_EVENT_MASK`	The event mask for selecting adjustment events.
`static final long`	`COMPONENT_EVENT_MASK`	The event mask for selecting component events.
`protected boolean`	`consumed`	Controls whether or not the event is sent back down to the peer once the source has processed it - false means it's sent to the peer; true means it's not.
`static final long`	`CONTAINER_EVENT_MASK`	The event mask for selecting container events.
`static final long`	`FOCUS_EVENT_MASK`	The event mask for selecting focus events.
`static final long`	`HIERARCHY_BOUNDS_EVENT_MASK`	The event mask for selecting hierarchy bounds events.
`static final long`	`HIERARCHY_EVENT_MASK`	The event mask for selecting hierarchy events.
`protected int`	`id`	The event's id.
`static final long`	`INPUT_METHOD_EVENT_MASK`	The event mask for selecting input method events.
`static final long`	`INVOCATION_EVENT_MASK`	The event mask for selecting invocation events.
`static final long`	`ITEM_EVENT_MASK`	The event mask for selecting item events.
`static final long`	`KEY_EVENT_MASK`	The event mask for selecting key events.
`static final long`	`MOUSE_EVENT_MASK`	The event mask for selecting mouse events.
`static final long`	`MOUSE_MOTION_EVENT_MASK`	The event mask for selecting mouse motion events.
`static final long`	`MOUSE_WHEEL_EVENT_MASK`	The event mask for selecting mouse wheel events.
`static final long`	`PAINT_EVENT_MASK`	The event mask for selecting paint events.
`static final int`	`RESERVED_ID_MAX`	The maximum value for reserved AWT event IDs.
`static final long`	`TEXT_EVENT_MASK`	The event mask for selecting text events.
`static final long`	`WINDOW_EVENT_MASK`	The event mask for selecting window events.
`static final long`	`WINDOW_FOCUS_EVENT_MASK`	The event mask for selecting window focus events.
`static final long`	`WINDOW_STATE_EVENT_MASK`	The event mask for selecting window state events.

Fields declared in class EventObject

source

Modifier and Type	Field	Description
`protected Object`	`source`	The object on which the Event initially occurred.

Constructor Summary

Constructor	Description
`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.
`FocusEvent(Component source, int id, boolean temporary, Component opposite)`	Constructs a `FocusEvent` object with the specified temporary state, opposite `Component` and the `Cause.UNKNOWN` cause.
`FocusEvent(Component source, int id, boolean temporary, Component opposite, FocusEvent.Cause cause)`	Constructs a `FocusEvent` object with the specified temporary state, opposite `Component` and the cause.

Method Summary

Modifier and Type	Method	Description
`final FocusEvent.Cause`	`getCause()`	Returns the event cause.
`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 declared in class ComponentEvent

getComponent

Modifier and Type	Method	Description
`Component`	`getComponent()`	Returns the originator of the event.

Methods declared in class AWTEvent

consume, getID, isConsumed, setSource, toString

Modifier and Type	Method	Description
`protected void`	`consume()`	Consumes this event, if this event can be consumed.
`int`	`getID()`	Returns the event type.
`protected boolean`	`isConsumed()`	Returns whether this event has been consumed.
`void`	`setSource(Object newSource)`	Retargets an event to a new source.
`String`	`toString()`	Returns a String representation of this object.

Methods declared in class EventObject

getSource

Modifier and Type	Method	Description
`Object`	`getSource()`	The object on which the Event initially occurred.

Methods declared in class Object

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

Modifier and Type	Method	Description
`protected Object`	`clone()`	Creates and returns a copy of this object.
`boolean`	`equals(Object obj)`	Indicates whether some other object is "equal to" this one.
`protected void`	`finalize()`	Deprecated, for removal: This API element is subject to removal in a future version. Finalization is deprecated and subject to removal in a future release.
`final Class<?>`	`getClass()`	Returns the runtime class of this `Object`.
`int`	`hashCode()`	Returns a hash code value for this object.
`final void`	`notify()`	Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()`	Wakes up all threads that are waiting on this object's monitor.
`final void`	`wait()`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
`final void`	`wait(long timeoutMillis)`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis, int nanos)`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

Field Details

FOCUS_FIRST

public static final int FOCUS_FIRST

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

See Also:

FOCUS_LAST

public static final int FOCUS_LAST

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

See Also:

FOCUS_GAINED

public static final int FOCUS_GAINED

This event indicates that the Component is now the focus owner.

See Also:

FOCUS_LOST

public static final int FOCUS_LOST

This event indicates that the Component is no longer the focus owner.

See Also:

Constructor Details

FocusEvent

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

Constructs a FocusEvent object with the specified temporary state, opposite Component and the Cause.UNKNOWN cause. 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.

This method throws an IllegalArgumentException if source is null.

Parameters:

source - The Component that originated the event

id - An integer indicating the type of event. For information on allowable values, see the class description for FocusEvent

temporary - Equals true if the focus change is temporary; false otherwise

opposite - The other Component involved in the focus change, or null

Throws:

IllegalArgumentException - if source equals null

Since:

1.4

See Also:

FocusEvent

public FocusEvent(Component source, int id, boolean temporary, Component opposite, FocusEvent.Cause cause)

Constructs a FocusEvent object with the specified temporary state, opposite Component and the cause. 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.

This method throws an IllegalArgumentException if source or cause is null.

Parameters:

source - The Component that originated the event

id - An integer indicating the type of event. For information on allowable values, see the class description for FocusEvent

temporary - Equals true if the focus change is temporary; false otherwise

opposite - The other Component involved in the focus change, or null

cause - The focus event cause.

Throws:

IllegalArgumentException - if source equals null or if cause equals null

Since:

See Also:

FocusEvent

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

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

This method throws an IllegalArgumentException if source is null.

Parameters:

source - The Component that originated the event

id - An integer indicating the type of event. For information on allowable values, see the class description for FocusEvent

temporary - Equals true if the focus change is temporary; false otherwise

Throws:

IllegalArgumentException - if source equals null

See Also:

FocusEvent

public FocusEvent(Component source, int id)

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

This method throws an IllegalArgumentException if source is null.

Parameters:

source - The Component that originated the event

id - An integer indicating the type of event. For information on allowable values, see the class description for FocusEvent

Throws:

IllegalArgumentException - if source equals null

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

public Component 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 with no other Component, then null is returned.

Returns:: the other Component involved in the focus change, or null
Since:: 1.4

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

getCause

public final FocusEvent.Cause getCause()

Returns the event cause.

Returns:: one of FocusEvent.Cause values
Since:: 9

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