C#委托和事件的使用实例

// 热水器
    public class Heater
    {
        private int temperature;
        public string type = "RealFire 001";       // 添加型号作为演示
        public string area = "China Xian";         // 添加产地作为演示
        //声明委托
        public delegate void BoiledEventHandler(Object sender, BoiledEventArgs e);
        public event BoiledEventHandler Boiled; //声明事件

        // 定义BoiledEventArgs类,传递给Observer所感兴趣的信息
        public class BoiledEventArgs : EventArgs
        {
            public readonly int temperature;
            public BoiledEventArgs(int temperature)
            {
                this.temperature = temperature;
            }
        }
        // 可以供继承自 Heater 的类重写,以便继承类拒绝其他对象对它的监视
        protected virtual void OnBoiled(BoiledEventArgs e)
        {
            if (Boiled != null)
            { // 如果有对象注册
                Boiled(this, e);  // 调用所有注册对象的方法
            }
        }

        // 烧水。(第一次调用该方法)
        public void BoilWater()
        {
            for (int i = 0; i <= 100; i++)
            {
                temperature = i;
                if (temperature > 98)
                {
                    //建立BoiledEventArgs 对象。
                    BoiledEventArgs e = new BoiledEventArgs(temperature);
                    OnBoiled(e);  // 调用 OnBolied方法(触发事件的方法)
                }
            }
        }
    }

    // 警报器
    public class Alarm
    {
        public void MakeAlert(Object sender, Heater.BoiledEventArgs e)
        {
            Heater heater = (Heater)sender;
            //访问 sender 中的公共字段
            Console.WriteLine("Alarm:{0} - {1}: ", heater.area, heater.type);
            Console.WriteLine("Alarm: 嘀嘀嘀,水已经 {0} 度了:", e.temperature);
            Console.WriteLine();
        }
    }

    // 显示器
    public class Display
    {
        public static void ShowMsg(Object sender, Heater.BoiledEventArgs e)
        {   //静态方法
            Heater heater = (Heater)sender;
            Console.WriteLine("Display:{0} - {1}: ", heater.area, heater.type);
            Console.WriteLine("Display:水快烧开了,当前温度:{0}度。", e.temperature);
            Console.WriteLine();
        }
    }

    class Program
    {
       public static void Main()
        {
            Heater heater = new Heater();
            Alarm alarm = new Alarm();

            heater.Boiled += alarm.MakeAlert;   //注册方法
            heater.Boiled += (new Alarm()).MakeAlert; //给匿名对象注册方法
            heater.Boiled += new Heater.BoiledEventHandler(alarm.MakeAlert); //也可以这么注册
            heater.Boiled += Display.ShowMsg;   //注册静态方法

            heater.BoilWater();   //烧水,会自动调用注册过对象的方法(按照顺序调用)
        }
    }

posted on 2012-02-27 14:14  初雪之恋  阅读(...)  评论(... 编辑 收藏

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