info.pppc.base.system.event

Class Event

java.lang.Object

info.pppc.base.system.event.Event

public class Event
extends java.lang.Object

An event is an object with a source (its creator), some user specified data that is event specific, a type (that is typically globally known). There are two types of events: undoable events and non undoable events. Undoable events support an undo operation that will lead to a roll back. Non undoable events will be performed no matter what status the system is in. The semantic of a specific event depends on the event source. This includes the point in time in which an event is reported (i.e. whether is reported synchronously, asynchronously, before the change or after the change). This means that users should read the comments. Note that an event type should be modeled by a single bit (although it is possible to use multiple bit masks to denote one event, it is discouraged in general).

Author:

Marcus Handte

Field Summary

Fields

Modifier and Type	Field and Description
static int	EVENT_EVERYTHING A constant that denotes all types.
static int	EVENT_NOTHING A constant that denotes no type.

Constructor Summary

Constructors

Constructor and Description
Event(int type, java.lang.Object source, java.lang.Object data, boolean undoable) Creates a new event with the specified type, source and user data.

Method Summary

Methods

Modifier and Type	Method and Description
java.lang.Object	getData() Returns the user data object contained in the event.
java.lang.Object	getSource() Returns the source object that created the event.
int	getType() Returns the type of the event as an integer constant.
boolean	isType(int t) Determines whether the event is also of the specified type, i.e.
boolean	isUndo() Determines whether this is an undo event.
boolean	isUndoable() Determines whether the specified event is undoable.
java.lang.String	toString() Returns a human readable string representation of this event.
void	undo() Cancels the event.

Methods inherited from class java.lang.Object

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

Field Detail

EVENT_NOTHING

public static int EVENT_NOTHING

A constant that denotes no type. This constant is the default value for an event.

EVENT_EVERYTHING

public static int EVENT_EVERYTHING

A constant that denotes all types. This constant can be used to subscribe to all event types.

Constructor Detail

Event

public Event(int type,
     java.lang.Object source,
     java.lang.Object data,
     boolean undoable)

Creates a new event with the specified type, source and user data. The undoable flag determines whether the event can be undone.

Parameters:

type - The type of the event. It is convention that an event type should only contain one active bit.

source - The source of the event.

data - The data of the event.

undoable - A flag that indicates whether the event can be aborted.

Method Detail

getType

public int getType()

Returns the type of the event as an integer constant.

Returns:

The type of the event.

isType

public boolean isType(int t)

Determines whether the event is also of the specified type, i.e. if the bitmask to test is completely contained in the bitmask that is used by the event.

Parameters:

t - The type to test for.

Returns:

True if the type is completely contained in the specified bitmask type definition.

getSource

public java.lang.Object getSource()

Returns the source object that created the event.

Returns:

The source object that created the event.

getData

public java.lang.Object getData()

Returns the user data object contained in the event.

Returns:

The user data object of the event.

isUndoable

public boolean isUndoable()

Determines whether the specified event is undoable. Returns true if the event can be undone and false if it cannot. If it cannot be undone, it is illegal to set the perform flag.

Returns:

True if the event can be undone, false if it cannot.

isUndo

public boolean isUndo()

Determines whether this is an undo event. An undo event is created from an undoable event when the event is undone by some listener. At that point an undo event will be created and typically it will be sent to all listeners that have already processed the event.

Returns:

Determines whether this is the undo operation of some event that has been created and processed earlier.

undo

public void undo()

Cancels the event. A typical event source will inform all listeners that have already been notified that this event should be canceled.

Throws:

java.lang.RuntimeException - Thrown if the event is not undoable or if the event is an undo event.

toString

public java.lang.String toString()

Returns a human readable string representation of this event.

Overrides:

toString in class java.lang.Object

Returns:

A human readable string representation of the event.