org.gvsig.tools.observer.impl

Class BaseWeakReferencingObservable

java.lang.Object

org.gvsig.tools.observer.impl.BaseWeakReferencingObservable

All Implemented Interfaces:

Cloneable, ComplexObservable, ComplexWeakReferencingObservable, Observable, WeakReferencingObservable

Direct Known Subclasses:

DefaultFolderSet, DelegateWeakReferencingObservable

public class BaseWeakReferencingObservable
extends Object
implements ComplexWeakReferencingObservable, Cloneable

Implementation for observers based on the use of Reference, instead of direct Observer references. This way an Observer may be Garbagge collected if its unique reference is the one registered into the Observable.

Author:

José Manuel Vivó, Cèsar Ordiñana

Constructor Summary

Constructors

Constructor and Description
BaseWeakReferencingObservable()

Method Summary

Methods

Modifier and Type	Method and Description
void	addObserver(Observer observer) Adds an observer to the set of observers for this object, provided that it is not the same as some observer already in the set.
void	addObserver(Reference ref)
void	addObservers(BaseWeakReferencingObservable observable)
void	beginComplexNotification() Sets the Observable in complex notification mode.
protected void	clearChanged() Indicates that this object has no longer changed, or that it has already notified all of its observers of its most recent change, so that the hasChanged method will now return false.
Object	clone()
int	countObservers() Returns the number of observers of this object.
void	deleteObserver(Observer observer) Deletes an observer from the set of observers of this object.
void	deleteObserver(Reference ref)
void	deleteObservers() Clears the observer list so that this object no longer has any observers.
void	disableNotifications() Disable the notification of events to registered Observers.
void	enableNotifications() Enable (default) the notification of events to registered Observers.
void	endComplexNotification() Ends the complex notification mode.
protected boolean	hasChanged() Tests if this object has changed.
boolean	inComplex()
boolean	isEnabledNotifications()
protected void	notify(WeakReferencingObservable observable, Object notification)
void	notifyObservers() If this object has changed, as indicated by the hasChanged method, then notify all of its observers and then call the clearChanged method to indicate that this object has no longer changed.
void	notifyObservers(Object arg) If this object has changed, as indicated by the hasChanged method, then notify all of its observers and then call the clearChanged method to indicate that this object has no longer changed.
protected void	setChanged() Marks this DefaultObservable object as having been changed; the hasChanged method will now return true.

Methods inherited from class java.lang.Object

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

Constructor Detail

BaseWeakReferencingObservable

public BaseWeakReferencingObservable()

Method Detail

addObserver

public void addObserver(Observer observer)

Adds an observer to the set of observers for this object, provided that it is not the same as some observer already in the set. The order in which notifications will be delivered to multiple observers is not specified. See the class comment.

Specified by:

addObserver in interface Observable

Parameters:

observer - an observer to be added.

Throws:

NullPointerException - if the parameter o is null.

addObserver

public void addObserver(Reference ref)

addObservers

public void addObservers(BaseWeakReferencingObservable observable)

deleteObserver

public void deleteObserver(Observer observer)

Deletes an observer from the set of observers of this object. Passing null to this method will have no effect.

Specified by:

deleteObserver in interface Observable

Parameters:

observer - the observer to be deleted.

deleteObserver

public void deleteObserver(Reference ref)

notifyObservers

public void notifyObservers()

If this object has changed, as indicated by the hasChanged method, then notify all of its observers and then call the clearChanged method to indicate that this object has no longer changed.

Each observer has its update method called with two arguments: this observable object and null. In other words, this method is equivalent to:

notifyObservers(null)

See Also:

Observable.clearChanged(), Observable.hasChanged(), Observer.update(java.util.Observable, java.lang.Object)

notifyObservers

public void notifyObservers(Object arg)

If this object has changed, as indicated by the hasChanged method, then notify all of its observers and then call the clearChanged method to indicate that this object has no longer changed.

Each observer has its update method called with two arguments: this observable object and the arg argument. public void visit(Object obj) throws VisitCanceledException, BaseException { // TODO Auto-generated method stub }

Parameters:

arg - any object.

See Also:

Observable.clearChanged(), Observable.hasChanged(), Observer.update(java.util.Observable, java.lang.Object)

deleteObservers

public void deleteObservers()

Clears the observer list so that this object no longer has any observers.

Specified by:

deleteObservers in interface Observable

countObservers

public int countObservers()

Returns the number of observers of this object.

Returns:

the number of observers of this object.

enableNotifications

public void enableNotifications()

Description copied from interface: ComplexObservable

Enable (default) the notification of events to registered Observers.

Specified by:

enableNotifications in interface ComplexObservable

disableNotifications

public void disableNotifications()

Description copied from interface: ComplexObservable

Disable the notification of events to registered Observers.

Specified by:

disableNotifications in interface ComplexObservable

isEnabledNotifications

public boolean isEnabledNotifications()

inComplex

public boolean inComplex()

beginComplexNotification

public void beginComplexNotification()

Description copied from interface: ComplexObservable

Sets the Observable in complex notification mode. All notifications must be stored, until the mode ends, and then notify all Observers with all the notifications.

Specified by:

beginComplexNotification in interface ComplexObservable

endComplexNotification

public void endComplexNotification()

Description copied from interface: ComplexObservable

Ends the complex notification mode. All notifications stored while in complex notification mode, will be notified to the registered Observers.

If a observer is a ComplexObserver, it will be notified with a single DefaultComplexNotification instead of each of the notifications.

Some important notes to take into account when calling this method.

• Observers must not rely in the order used to perform the notifications. The notifications order is maintained, but the notification to all the observers might be performed for each notification to all observers, or for each observer all notifications.
• The notification process works as an atomic action, so if while an Observer is processing a notification another Observer is registered to the source Observable, it won't get any of the notifications currently being notified, but future ones.

Specified by:

endComplexNotification in interface ComplexObservable

clone

public Object clone()
             throws CloneNotSupportedException

Overrides:

clone in class Object

Throws:

CloneNotSupportedException

notify

protected void notify(WeakReferencingObservable observable,
          Object notification)

hasChanged

protected boolean hasChanged()

Tests if this object has changed.

Returns:

true if and only if the setChanged method has been called more recently than the clearChanged method on this object; false otherwise.

See Also:

Observable.clearChanged(), Observable.setChanged()

setChanged

protected void setChanged()

Marks this DefaultObservable object as having been changed; the hasChanged method will now return true.

clearChanged

protected void clearChanged()

Indicates that this object has no longer changed, or that it has already notified all of its observers of its most recent change, so that the hasChanged method will now return false. This method is called automatically by the notifyObservers methods.

See Also:

Observable.notifyObservers(), Observable.notifyObservers(java.lang.Object)