用于在android中更改变量的侦听器

Question

我的课程中有一个变量,我希望当变量发生变化时,我会在另一个类中执行操作.事实上我想要一个监听器来改变android中的变量(我的变量可能每分钟都在变化)

public class Connect { 
     public static boolean myBoolean;
//some actions do and myBoolean change   
}

public class Selection extends Activity implements OnMenuItemClickListener{

//I want a thing like listener here ,when myboolean changed I do an action (myboolean may change every minute)

} 

Answer 1

这是不可能直接的.但是,您可以将字段设为私有,添加getter和setter,并创建添加侦听器的方法(这称为Observer模式):

interface ConnectionBooleanChangedListener {
    public void OnMyBooleanChanged();
}

public class Connect { 
     private static boolean myBoolean;
     private static List<ConnectionBooleanChangedListener> listeners = new ArrayList<ConnectionBooleanChangedListener>();

     public static boolean getMyBoolean() { return myBoolean; }

     public static void setMyBoolean(boolean value) {
         myBoolean = value;

         for (ConnectionBooleanChangedListener l : listeners) {
             l.OnMyBooleanChanged();
         }
     }

     public static void addMyBooleanListener(ConnectionBooleanChangedListener l) {
         listeners.add(l);
     }
}

然后,无论您想要监听布尔值的更改,您都可以注册一个监听器:

Connect.addMyBooleanListener(new ConnectionBooleanChangedListener() {
    @Override
    public void OnMyBooleanChanged() {
        // do something
    }
});

添加一个删除侦听器的方法仍然是一个练习.显然,为了实现这一点,你需要确保myBoolean只通过setMyBoolean内部改变Connect.