当需要调用方法时，将该方法做成一个监听，AddListener（事件码，方法）委托需要与事件码绑定。方法若持有参数，在AddListener前指定同类型的泛型。

传统的方式是通过获取存在方法的类来调取或者采用单例模式实现，但是这样呢代码耦合性高，不易维护，本片博客总结实现事件监听机制完成方法调用。（跟消息发送机制类似）

首先，创建EventType.cs定义事件类型

public enum EventType
{
     
}

其次，创建CallBack.cs定义回调方法的委托类型

public delegate void CallBack();
public delegate void CallBack<T>(T arg);
public delegate void CallBack<T, X>(T arg1, X arg2);
public delegate void CallBack<T, X, Y>(T arg1, X arg2, Y arg3);

最后，创建Event.cs实现方法监听与移除监听（最重要的一环）

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Event
{
    private static Dictionary<EventType, Delegate> _EventTable = new Dictionary<EventType, Delegate>();

    #region
    private static void OnListenerAdding(EventType eventType, Delegate callBack)
    {
        if (!_EventTable.ContainsKey(eventType))
        {
            _EventTable.Add(eventType, null);
        }
        Delegate d = _EventTable[eventType];
        if (d != null && d.GetType() != callBack.GetType())
        {
            throw new Exception(string.Format("尝试为事件{0}添加不同类型的委托，当前事件所对应的委托是{1}，要添加的委托类型为{2}", eventType, d.GetType(), callBack.GetType()));
        }
    }
    private static void OnListenerRemoving(EventType eventType, Delegate callBack)
    {
        if (_EventTable.ContainsKey(eventType))
        {
            Delegate d = _EventTable[eventType];
            if (d == null)
            {
                throw new Exception(string.Format("移除监听错误：事件{0}没有对应的委托", eventType));
            }
            else if (d.GetType() != callBack.GetType())
            {
                throw new Exception(string.Format("移除监听错误：尝试为事件{0}移除不同类型的委托，当前委托类型为{1}，要移除的委托类型为{2}", eventType, d.GetType(), callBack.GetType()));
            }
        }
        else
        {
            throw new Exception(string.Format("移除监听错误：没有事件码{0}", eventType));
        }
    }
    private static void OnListenerRemoved(EventType eventType)
    {
        if (_EventTable[eventType] == null)
        {
            _EventTable.Remove(eventType);
        }
    }
    #endregion

    #region 添加监听
    //no parameters
    public static void AddListener(EventType eventType, CallBack callBack)
    {
        OnListenerAdding(eventType, callBack);
        _EventTable[eventType] = (CallBack)_EventTable[eventType] + callBack;
    }
    //Single parameters
    public static void AddListener<T>(EventType eventType, CallBack<T> callBack)
    {
        OnListenerAdding(eventType, callBack);
        _EventTable[eventType] = (CallBack<T>)_EventTable[eventType] + callBack;
    }
    //two parameters
    public static void AddListener<T, X>(EventType eventType, CallBack<T, X> callBack)
    {
        OnListenerAdding(eventType, callBack);
        _EventTable[eventType] = (CallBack<T, X>)_EventTable[eventType] + callBack;
    }
    //three parameters
    public static void AddListener<T, X, Y>(EventType eventType, CallBack<T, X, Y> callBack)
    {
        OnListenerAdding(eventType, callBack);
        _EventTable[eventType] = (CallBack<T, X, Y>)_EventTable[eventType] + callBack;
    }
    #endregion

    #region 移除监听
    //no parameters
    public static void RemoveListener(EventType eventType, CallBack callBack)
    {
        OnListenerRemoving(eventType, callBack);
        _EventTable[eventType] = (CallBack)_EventTable[eventType] - callBack;
        OnListenerRemoved(eventType);
    }
    //single parameters
    public static void RemoveListener<T>(EventType eventType, CallBack<T> callBack)
    {
        OnListenerRemoving(eventType, callBack);
        _EventTable[eventType] = (CallBack<T>)_EventTable[eventType] - callBack;
        OnListenerRemoved(eventType);
    }
    //two parameters
    public static void RemoveListener<T, X>(EventType eventType, CallBack<T, X> callBack)
    {
        OnListenerRemoving(eventType, callBack);
        _EventTable[eventType] = (CallBack<T, X>)_EventTable[eventType] - callBack;
        OnListenerRemoved(eventType);
    }
    //three parameters
    public static void RemoveListener<T, X, Y>(EventType eventType, CallBack<T, X, Y> callBack)
    {
        OnListenerRemoving(eventType, callBack);
        _EventTable[eventType] = (CallBack<T, X, Y>)_EventTable[eventType] - callBack;
        OnListenerRemoved(eventType);
    }
    #endregion

    #region 播报（执行）
    //no parameters
    public static void Broadcast(EventType eventType)
    {
        Delegate d;
        if (_EventTable.TryGetValue(eventType, out d))
        {
            CallBack callBack = d as CallBack;
            if (callBack != null)
            {
                callBack();
            }
            else
            {
                throw new Exception(string.Format("广播事件错误：事件{0}对应委托具有不同的类型", eventType));
            }
        }
    }
    //single parameters
    public static void Broadcast<T>(EventType eventType, T arg)
    {
        Delegate d;
        if (_EventTable.TryGetValue(eventType, out d))
        {
            CallBack<T> callBack = d as CallBack<T>;
            if (callBack != null)
            {
                callBack(arg);
            }
            else
            {
                throw new Exception(string.Format("广播事件错误：事件{0}对应委托具有不同的类型", eventType));
            }
        }
    }
    //two parameters
    public static void Broadcast<T, X>(EventType eventType, T arg1, X arg2)
    {
        Delegate d;
        if (_EventTable.TryGetValue(eventType, out d))
        {
            CallBack<T, X> callBack = d as CallBack<T, X>;
            if (callBack != null)
            {
                callBack(arg1, arg2);
            }
            else
            {
                throw new Exception(string.Format("广播事件错误：事件{0}对应委托具有不同的类型", eventType));
            }
        }
    }
    //three parameters
    public static void Broadcast<T, X, Y>(EventType eventType, T arg1, X arg2, Y arg3)
    {
        Delegate d;
        if (_EventTable.TryGetValue(eventType, out d))
        {
            CallBack<T, X, Y> callBack = d as CallBack<T, X, Y>;
            if (callBack != null)
            {
                callBack(arg1, arg2, arg3);
            }
            else
            {
                throw new Exception(string.Format("广播事件错误：事件{0}对应委托具有不同的类型", eventType));
            }
        }
    }
  
    #endregion
}

写在最后，如果监听方法有多个参数（我只扩展了1，2，3个参数），可按照上面代码方式进行扩展