unity 观察者模式应用(事件的广播和监听系统)

首先，分别新建以下三个脚本 脚本1，脚本名：CallBack

//定义了具有不同参数数量的委托类型，提供给EventCenter使用
public delegate void CallBack();
public delegate void CallBack(T arg);
public delegate void CallBack(T arg1, X arg2);
public delegate void CallBack(T arg1, X arg2, Y arg3);
public delegate void CallBack(T arg1, X arg2, Y arg3, Z arg4);
public delegate void CallBack(T arg1, X arg2, Y arg3, Z arg4, W arg5);

脚本名2：EventType

public enum EventType
{
    //定义枚举，为EventCenter提供事件类型
       ShowText,
}

脚本名3：EventCenter

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

public class EventCenter
{
    private static Dictionary m_EventTable = new Dictionary();

    //添加监听
    private static void OnListenerAdding(EventType eventType,Delegate callBack)
    {
        if (!m_EventTable.ContainsKey(eventType))
        {
            m_EventTable.Add(eventType, null);
        }
        Delegate d = m_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()));
        }
    }
    //移除监听
    private static void OnListenerRemoving(EventType eventType,Delegate callBack)
    {
        if (m_EventTable.ContainsKey(eventType))
        {
            Delegate d = m_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));
        }
    }
    //移除监听后，刷新监听事件列表
    public static void OnListenerRemoeved(EventType eventType)
    {
        if (m_EventTable[eventType] == null)
        {
            m_EventTable.Remove(eventType);
        }
    }

    //六种参数数量的添加监听方法
    //no parameters没有参数
    public static void AddListener(EventType eventType,CallBack callBack)
    {
        OnListenerAdding(eventType, callBack);
         m_EventTable[eventType] = (CallBack)m_EventTable[eventType] + callBack;
    }
    //Single parametener一个参数
    public static void AddListener(EventType eventType, CallBack callBack)
    {
        OnListenerAdding(eventType, callBack);
        m_EventTable[eventType] = (CallBack)m_EventTable[eventType] + callBack;
    }
    //two parametener两个参数
    public static void AddListener(EventType eventType, CallBack callBack)
    {
        OnListenerAdding(eventType, callBack);
        m_EventTable[eventType] = (CallBack)m_EventTable[eventType] + callBack;
    }
    //three parametener三个参数
    public static void AddListener(EventType eventType, CallBack callBack)
    {
        OnListenerAdding(eventType, callBack);
        m_EventTable[eventType] = (CallBack)m_EventTable[eventType] + callBack;
    }
    //four parametener四个参数
    public static void AddListener(EventType eventType, CallBack callBack)
    {
        OnListenerAdding(eventType, callBack);
        m_EventTable[eventType] = (CallBack)m_EventTable[eventType] + callBack;
    }
    //five parametener五个参数
    public static void AddListener(EventType eventType, CallBack callBack)
    {
        OnListenerAdding(eventType, callBack);
        m_EventTable[eventType] = (CallBack)m_EventTable[eventType] + callBack;
    }

    //六种参数数量情况下的事件移除方法
    //no parameters
    public static void RemoveListener(EventType eventType,CallBack callBack)
    {
        OnListenerRemoving(eventType, callBack);
        m_EventTable[eventType] = (CallBack)m_EventTable[eventType] - callBack;
        OnListenerRemoeved(eventType);
    }
    //Single parameters
    public static void RemoveListener(EventType eventType, CallBack callBack)
    {
        OnListenerRemoving(eventType, callBack);
        m_EventTable[eventType] = (CallBack)m_EventTable[eventType] - callBack;
        OnListenerRemoeved(eventType);
    }
    //two parameters
    public static void RemoveListener(EventType eventType, CallBack callBack)
    {
        OnListenerRemoving(eventType, callBack);
        m_EventTable[eventType] = (CallBack)m_EventTable[eventType] - callBack;
        OnListenerRemoeved(eventType);
    }
    //three parameters
    public static void RemoveListener(EventType eventType, CallBack callBack)
    {
        OnListenerRemoving(eventType, callBack);
        m_EventTable[eventType] = (CallBack)m_EventTable[eventType] - callBack;
        OnListenerRemoeved(eventType);
    }
    //four parameters
    public static void RemoveListener(EventType eventType, CallBack callBack)
    {
        OnListenerRemoving(eventType, callBack);
        m_EventTable[eventType] = (CallBack)m_EventTable[eventType] - callBack;
        OnListenerRemoeved(eventType);
    }
    //five parameters
    public static void RemoveListener(EventType eventType, CallBack callBack)
    {
        OnListenerRemoving(eventType, callBack);
        m_EventTable[eventType] = (CallBack)m_EventTable[eventType] - callBack;
        OnListenerRemoeved(eventType);
    }

    //六种参数数量情况下的广播方法
    //no parameters
    public static void Broadcast(EventType eventType)
    {
        Delegate d;
        if (m_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(EventType eventType,T arg)
    {
        Delegate d;
        if (m_EventTable.TryGetValue(eventType, out d))
        {
            CallBack callBack = d as CallBack;
            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(EventType eventType, T arg1,X arg2)
    {
        Delegate d;
        if (m_EventTable.TryGetValue(eventType, out d))
        {
            CallBack callBack = d as CallBack;
            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(EventType eventType, T arg1, X arg2, Y arg3)
    {
        Delegate d;
        if (m_EventTable.TryGetValue(eventType, out d))
        {
            CallBack callBack = d as CallBack;
            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));
            }
        }
    }
    //four parameters
    public static void Broadcast(EventType eventType, T arg1, X arg2, Y arg3, Z arg4)
    {
        Delegate d;
        if (m_EventTable.TryGetValue(eventType, out d))
        {
            CallBack callBack = d as CallBack;
            if (callBack != null)
            {
                callBack(arg1, arg2, arg3, arg4);
            }
            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));
            }
        }
    }
    //five parameters
    public static void Broadcast(EventType eventType, T arg1, X arg2, Y arg3, Z arg4, W arg5)
    {
        Delegate d;
        if (m_EventTable.TryGetValue(eventType, out d))
        {
            CallBack callBack = d as CallBack;
            if (callBack != null)
            {
                callBack(arg1, arg2, arg3, arg4, arg5);
            }
            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));
            }
        }
    }
}

场景中新建button，添加一个脚本：

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

public class BtnClick : MonoBehaviour {

    private void Awake()
    {
        GetComponent().onClick.AddListener(() => {
            //按下按钮，发送广播
            EventCenter.Broadcast(EventType.ShowText,"你好","吗",3.0F,6,5);
        });
    }
}

场景中新建一个text，添加一个脚本：

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

public class ShowText : MonoBehaviour
{
    private void Awake()
    {
        gameObject.SetActive(false);
        //添加广播监听，并绑定事件方法为Show
        EventCenter.AddListener(EventType.ShowText, Show);
    }

    private void OnDestroy()
    {
        //移除广播监听
        EventCenter.RemoveListener(EventType.ShowText, Show);
    }

    public void Show(string str, string str1, float a, int b, int c)
    {
        gameObject.SetActive(true);
        GetComponent().text = str + str1 + a + b + c;

    }
}

脚本准备完毕， 把text多复制几份像下图这样 运行场景，点击button，你会发现，BtnClick脚本里发送的广播消息，被显示在了text上，然而button和text之间并没有直接的相互干预(所有的Text上只要挂了脚本“ShowText ”，就都能同一时间接收到btnClick中发送的消息)，这就是观察者模式的作用了。 观察者模式的好处就是，避免了在脚本组件上拖拽物体的方式，降低了代码耦合度。在CallBack中我们定义了CallBack的多个重写，是为了应对不同参数数量的情况。

注意事项：在我们需要更改消息参数数量的时候需要同步在发送时（BtnClick中）、接收时（ShowText中）的参数数量，然后如果CallBack脚本中没有你想使用的委托类型你需要新增，EventCenter脚本中也要添加对应的事件“添加、删除、广播”三种方法

参考视频：http://www.sikiedu.com/my/course/304