A detailed explanation of the Observer mode (Observer pattern)

Observer mode (Observer pattern): Defines a one-to-many dependency between objects, so that when an object changes state, all its dependents are notified and automatically updated.

How to use:

1. First new theme (subject) interface, responsible for registration (register) Delete (remove) \ Notice (notify) observer; Observer (Observer) interface, responsible for updating (update) data;

Subject (subject) Interface: Registered observer (REGISTEROBSERVER), delete Observer (Removeobserver), notify the Observer (Notifyobservers, notify all observers);

Observer (Observer) interface: Updates (update);

Code:

/** 
 * @time May 22, 2014 * * *
package observer;  
      
/** 
 * @author C.l.wang 
 * 
 *
/public interface Subject {public  
    void Registerobserver (Observer o); c10/>public void Removeobserver (Observer o);  
    public void Notifyobervers ();  
}  
      
      
/** 
 * @time May 22, 2014 * * *
package observer;  
      
/** 
 * @author C.l.wang 
 * 
 *
/public interface Observer {public  
    void update (float temp, float Humidity, float pressure);  
      
      
/** 
 * @time May 22, 2014 * * *
package observer;  
      
/** 
 * @author C.l.wang 
 * 
 *
/public interface Displayelement {public  
    void display ();  
}

2. Implementing the subject (subject) interface, registering (register) and Deleting (remove) observer in the form of lists (list),

Notifies (notify) The observer, iterates through the update (update) Action of all registered observers;

Through an interface function (set), encapsulates the notification (notify) action, passing in the parameters and notifying.

Code:

/** * @time May 22, 2014 * * * Package observer;  
      
Import java.util.ArrayList; /** * @author C.l.wang * */public class Weatherdata implements Subject {public arraylist<obser  
    Ver> observers;  
    private float temperature; private float humidity;  
          
    Humidity private float pressure;  
    Public Weatherdata () {observers = new arraylist<observer> (); }/* (NON-JAVADOC) * @see Observer. SUBJECT#REGISTEROBSERVER (Observer. Observer) */@Override public void Registerobserver (Observer o) {//TODO auto-generated Metho  
    D stub Observers.add (o); }/* (NON-JAVADOC) * @see Observer. SUBJECT#REMOVEOBSERVER (Observer. Observer) */@Override public void Removeobserver (Observer o) {//TODO auto-generated method  
        stub int i = Observers.indexof (o); if (i>=0) {Observers.remove (i); }/* (NON-JAVADOC) * @see Observer.  Subject#notifyobervers () */@Override public void Notifyobervers () {//TODO auto-generated method  
            Stub for (int i=0; i<observers.size (); ++i) {Observer Observer = (Observer) observers.get (i);  
        Observer.update (temperature, humidity, pressure);  
    } public void Measurementschanged () {notifyobervers (); public void setmeasurements (float temperature, float humidity, float pressure) {This.tempera  
        ture = temperature;  
        this.humidity = humidity;  
        This.pressure = pressure;  
    Measurementschanged (); }  
      
}