自定義監聽器

解決的問題：

現實處理邏輯中，我們經常遇到這種邏輯，當msg="放假了"的時候，Teacher,Student,Parent分別做出相應的動作(doMyEvent)

一般這樣寫：

if( msg.equalsIgnoreCase("放假了")){
    teacher.doMyEvent();
    student.doMyEvent();
    parent.doMyEvent();
}

每次有消息發送過來，都要寫這幾行，顯然太麻煩，我們採用監視器，註冊一次，就可對消息進行分發

1. 定義接口 

public interface MyListener {
    public void doMyEvent();
}

2.定義Teacher/Student/Parent的實現類

public class TeacherListener implements MyListener {

    @Override
    public void doMyEvent() {
        // TODO Auto-generated method stub
        System.out.println("老師舒心了");
    }

}

public class StudentListener implements MyListener {

    @Override
    public void doMyEvent() {
        // TODO Auto-generated method stub
        System.out.println("學生開心了");
    }

}

 

public class ParentListener implements MyListener {

    @Override
    public void doMyEvent() {
        // TODO Auto-generated method stub
        System.out.println("父母鬧心了");
    }

}

3.定義消息分發器

public class MyNotice {
    //監聽器容器
    private List<MyListener> listener = new ArrayList<MyListener>();
    //給事件綁定監聽器
    public void addMyListener(MyListener ren) {
        listener.add(ren);
    }
    //事件觸發器
    public void tellMe(String msg) {
        if(msg.equalsIgnoreCase("放假了")) {
            Iterator<MyListener> iterator = listener.iterator();
            while(iterator.hasNext()) {
                MyListener ren = iterator.next();
                ren.doMyEvent();
            }
        }
    }
}

4.定義main函數

public class Main {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        MyNotice notice = new MyNotice(); 
        notice.addMyListener(new TeacherListener());
        notice.addMyListener(new StudentListener());
        notice.addMyListener(new ParentListener());
        
        String msg = "放假了";
        notice.tellMe(msg);
    }

}