java.awt.event

Class ActionEvent

java.lang.Object

java.util.EventObject

java.awt.AWTEvent

java.awt.event.ActionEvent

All Implemented Interfaces:

Serializable

public class ActionEvent
extends AWTEvent

A semantic event which indicates that a component-defined action occurred. This high-level event is generated by a component (such as a Button) when the component-specific action occurs (such as being pressed). The event is passed to every ActionListener object that registered to receive such events using the component's addActionListener method.

Note: To invoke an ActionEvent on a Button using the keyboard, use the Space bar.

The object that implements the ActionListener interface gets this ActionEvent when the event occurs. The listener is therefore spared the details of processing individual mouse movements and mouse clicks, and can instead process a "meaningful" (semantic) event like "button pressed".

Since:

1.1

See Also:

ActionListener, Tutorial: Java 1.1 Event Model, Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static int	ACTION_FIRST The first number in the range of ids used for action events.
static int	ACTION_LAST The last number in the range of ids used for action events.
static int	ACTION_PERFORMED This event id indicates that a meaningful action occured.
static int	ALT_MASK The alt modifier.
static int	CTRL_MASK The control modifier.
static int	META_MASK The meta modifier.
static int	SHIFT_MASK The shift modifier.

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

Constructors

Constructor and Description
ActionEvent(Object source, int id, String command) Constructs an ActionEvent object.
ActionEvent(Object source, int id, String command, int modifiers) Constructs an ActionEvent object with modifier keys.
ActionEvent(Object source, int id, String command, long when, int modifiers) Constructs an ActionEvent object with the specified modifier keys and timestamp.

Method Summary

Methods

Modifier and Type	Method and Description
String	getActionCommand() Returns the command string associated with this action.
int	getModifiers() Returns the modifier keys held down during this action event.
long	getWhen() Returns the timestamp of when this event occurred.
String	paramString() Returns a parameter string identifying this action 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

SHIFT_MASK

public static final int SHIFT_MASK

The shift modifier. An indicator that the shift key was held down during the event.

See Also:

Constant Field Values

CTRL_MASK

public static final int CTRL_MASK

The control modifier. An indicator that the control key was held down during the event.

See Also:

Constant Field Values

META_MASK

public static final int META_MASK

The meta modifier. An indicator that the meta key was held down during the event.

See Also:

Constant Field Values

ALT_MASK

public static final int ALT_MASK

The alt modifier. An indicator that the alt key was held down during the event.

See Also:

Constant Field Values

ACTION_FIRST

public static final int ACTION_FIRST

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

See Also:

Constant Field Values

ACTION_LAST

public static final int ACTION_LAST

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

See Also:

Constant Field Values

ACTION_PERFORMED

public static final int ACTION_PERFORMED

This event id indicates that a meaningful action occured.

See Also:

Constant Field Values

Constructor Detail

ActionEvent

public ActionEvent(Object source,
           int id,
           String command)

Constructs an ActionEvent object.

Note that passing in an invalid id results in unspecified behavior. This method throws an IllegalArgumentException if source is null. A null command string is legal, but not recommended.

Parameters:

source - the object that originated the event

id - an integer that identifies the event

command - a string that may specify a command (possibly one of several) associated with the event

Throws:

IllegalArgumentException - if source is null

ActionEvent

public ActionEvent(Object source,
           int id,
           String command,
           int modifiers)

Constructs an ActionEvent object with modifier keys.

Note that passing in an invalid id results in unspecified behavior. This method throws an IllegalArgumentException if source is null. A null command string is legal, but not recommended.

Parameters:

source - the object that originated the event

id - an integer that identifies the event

command - a string that may specify a command (possibly one of several) associated with the event

modifiers - the modifier keys held down during this action

Throws:

IllegalArgumentException - if source is null

ActionEvent

public ActionEvent(Object source,
           int id,
           String command,
           long when,
           int modifiers)

Constructs an ActionEvent object with the specified modifier keys and timestamp.

Note that passing in an invalid id results in unspecified behavior. This method throws an IllegalArgumentException if source is null. A null command string is legal, but not recommended.

Parameters:

source - the object that originated the event

id - an integer that identifies the event

command - a string that may specify a command (possibly one of several) associated with the event

when - the time the event occurred

modifiers - the modifier keys held down during this action

Throws:

IllegalArgumentException - if source is null

Since:

1.4

Method Detail

getActionCommand

public String getActionCommand()

Returns the command string associated with this action. This string allows a "modal" component to specify one of several commands, depending on its state. For example, a single button might toggle between "show details" and "hide details". The source object and the event would be the same in each case, but the command string would identify the intended action.

Note that if a null command string was passed to the constructor for this ActionEvent, this this method returns null.

Returns:

the string identifying the command for this event

getWhen

public long getWhen()

Returns the timestamp of when this event occurred. Because an ActionEvent is a high-level, semantic event, the timestamp is typically the same as an underlying InputEvent.

Returns:

this event's timestamp

Since:

1.4

getModifiers

public int getModifiers()

Returns the modifier keys held down during this action event.

Returns:

the bitwise-or of the modifier constants

paramString

public String paramString()

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

Overrides:

paramString in class AWTEvent

Returns:

a string identifying the event and its associated command