Interface dnx.util.DNXObservable 
All Packages  Class Hierarchy  This Package  Previous  Next  Index

Interface dnx.util.DNXObservable

public interface DNXObservable
extends Object
This class provides a lower-level and more flexible paradigm than the standard Java Observable class paradigm. In this paradigm, objects that want to be observed implement the DNXObservable interface, and create a DNXObservableEngine as necessary to handle the observation mechanism. If you don't need the power of this paradigm and the simpler Java-style paradigm is sufficient, you can also use DNXJavaStyleObservable, which is implemented using this paradigm. Here are some reasons for the different paradigm: 1) The most important reason is that in the standard Observable class, the notifyObservers() method synchronizes around the entire method call on the Observable. This tends to cause deadlocks when multiple threads are sending and receiving updates. There is basically no way to work around this using the standard Observable class. 2) The standard Observable class inherits from Object, not DNXObject. This is a problem because we want everything to inherit from DNXObject, so we have standard assert() methods in every class. Here once again we are screwed by the cursed lack of multiple inheritance in Java. 3) The standard Observable class bogusly requires two method calls to do the equivalent of our updateObservers(). Not only does this require us to synchronize around the two calls to avoid race conditions (which conflicts with #1), but one of the two methods (setChanged()) is declared protected, making it impossible without further kludgery for various classes to send updates on behalf of another class's object. 4) Inheriting from an Observable class causes the object to always take up extra space, rather than doing so only when necessary (e.g. by allocating the DNXObservableEngine and storing it into an "aux-data" structure, like for Node).

Method Index

o addObserver(DNXObserver)
o addObserver(DNXObserver, int)
o countObservers()
o deleteObserver(DNXObserver)
o deleteObservers()
o getObservableEngine()
o getObserverEventMask()

Methods

o getObservableEngine 
  public abstract DNXObservableEngine getObservableEngine()
o getObserverEventMask 
  public abstract int getObserverEventMask()
o addObserver 
  public abstract void addObserver(DNXObserver o)
o addObserver 
  public abstract void addObserver(DNXObserver o,
                                   int mask)
o countObservers 
  public abstract int countObservers()
o deleteObserver 
  public abstract void deleteObserver(DNXObserver o)
o deleteObservers 
  public abstract void deleteObservers()

All Packages  Class Hierarchy  This Package  Previous  Next  Index