Observer mode (listener, listener)

In fact, the truth is very simple.

 

[Listener]

I want to listen to something, so I must have a listener/or an observer.Myobserver.

There is a method in my listener to process the listened data.Update ().

So:

(1) What are the requirements of listener and method? That is, the interface provided by the listener must be implemented.Observer

(2) How can I register this listener with the listener? There are many methods. For example, the listener provides a singleton Class C, which allows the caller to call C. getinstance (). setlistener (ourlistener );Add

 

[Listener]

The listener usually maintains a list <listener>. After a Dongdong changes, it notifies all listeners (for () to call listener cyclically. method (), so the listener is implemented.

 

[Just talk about it]

The listened party can use its own thread to notify all listeners, or call its own thread pool for processing.

I personally prefer the latter, because ifProgramComplicated: the thread pool of the listener itself can be asynchronously used to free the listener thread.

 

The listener can either be new or bean assembled. It doesn't matter.

 

 

[Program appearance]

 

[1] Subject interface observer

 
Class observer {
 

 
Notify ();
 

 
}
 

[2] caller myobserver

 
Class mylistener {
 

 
Observer listener = new myobserver ();// New and assembled
 

 
PublicVoid dobizoperation (){
 

 
}
 

 
Class myobserver implements observer {
 

 
Notify (){
 

 
}
 

 
}
 

 
}
 

[3] called Subject

 
Class subject {
 

 
List <interfacebycalled> listeners = new list <interfacebycalled> ();
 

 
PublicVoid setlistener (interfacebycalled listener ){
 

 
Listeners.Add(Listener );
 

 
}
 

PublicList <observer> informlisteners (){
 

 
For(Observer listener: This. Listeners ){
 

 
Listener. Policy ();
 

 
}
}
 

 
}
 

[4] At last, inject mylistener into subject.

Observer observer = mylistener. getlistener ();

Subject. setlistener (observer );