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# java 事件(java Event)
# java.util.Eventobject,java.util.EventListener

Java 事件处理机制

java中的事件机制的参与者有3种角色：
    1. event object：事件状态对象,是一类事件的实例。
        伴随着事件的发生，相应的状态通常都封装在事件状态对象中，该对象必须继承自java.util.EventObject。事件状态对象作为单参传递给应响应该事件的监听者方法中。
    2. event source：具体的事件源,事件的生产者。
        发出某种特定事件的事件源的标识是：遵从规定的设计格式为事件监听者定义注册方法，并接受对指定事件监听者接口实例的引用。
    3. event listener：事件监听者,事件的消费者。
        具体的对监听的事件类，当它监听到event object产生的时候，它就调用相应的方法，进行处理。

<Note>
    public interface EventListener：所有事件侦听器接口必须扩展的标记接口。
    public class EventObject extends Object implements Serializable。所有事件状态对象都将从其派生的根类。 所有 Event 在构造时都引用了对象 "source"，在逻辑上认为该对象是最初发生有关 Event 的对象。

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运行结果：

Console>> Console is started.
lights>> lights are changing.
Light 0>> is off
Light 1>> is off
Light 2>> is on
Light 3>> is off
Light 4>> is on
Light 5>> is on
Light 6>> is off
Light 7>> is on
Light 8>> is on
Light 9>> is on
lights>> lights are changing.
Light 0>> is on
Light 1>> is on
Light 2>> is on
Light 3>> is on
Light 4>> is off
Light 5>> is on
Light 6>> is on
Light 7>> is off
Light 8>> is on
Light 9>> is off

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JAVA CODE：

1. 定义事件对象

package event;import java.util.EventObject;public class LightEvent extends EventObject {private static final long serialVersionUID = -1256654879784096588L;private boolean lightstate = false; private String lightname;public String getLightname() {return lightname;}public boolean getLightstate() {return lightstate;}public LightEvent(Object source,String name,boolean state) {super(source);this.lightstate = state;this.lightname = name;}}

2. 定义事件监听接口和具体的监听者类

package event;import java.util.EventListener;public interface lightlistener extends EventListener {public abstract void listenlight (LightEvent event);
}package event;public class lightlistener1 implements lightlistener{public void listenlight (LightEvent event){if(event.getLightstate()){System.out.println(""+event.getLightname()+">> is on");}else{System.out.println(""+event.getLightname()+">> is off");}};}

3. 定义事件源和注册类

//register
package event;import java.util.*;public class listenerregister {public List<EventListener> listenerlist = new ArrayList<EventListener>();public void addListener(EventListener listener) {listenerlist.add(listener);}public void removeListener(EventListener listener) {listenerlist.remove(listener);}public void notifylisteners(LightEvent event){for(EventListener tmplistener : listenerlist){((lightlistener)tmplistener).listenlight(event);}}
}// EventSource
package event;import java.util.*;public class Console {private listenerregister register = new listenerregister();private boolean[] lights = new boolean[10] ;private Random randomer = new Random();public void setLights(boolean light, int index) {this.lights[index] = light;String name = "Light "+ index;LightEvent event = new LightEvent(this,name,light);notifylisteners(event);}public void notifylisteners(LightEvent event){register.notifylisteners(event);}public void addListener(EventListener listener) {register.listenerlist.add(listener);}public void removeListener(EventListener listener) {register.listenerlist.remove(listener);}public static void main(String[] args) throws InterruptedException {// TODO Auto-generated method stubSystem.out.println("Console>> Console is started.");Console console = new Console();console.addListener(new lightlistener1());while(true){System.out.println("lights>> lights are changing.");for(int i=0;i<10;i++){console.setLights(console.randomer.nextBoolean(), i);}Thread.sleep(1000);}}
}