Unity统一管理回调函数—观察者模式
发表于2018-06-08
我们来想象一个场景，在加载一个模型时，你需要从网上下载，但是你并不知道下载需要花费多少时间。你所知道的是，当下载完成后，就可以把模型放在特定位置上，开始游戏。那么，我们怎样才能判断下载完成呢？
一个简单的方法是，在每一帧的时候都判断下载是否完成，完成后就可以继续后面的工作。因此，我们可以这样做，我们告诉一个管理器，嗨，你帮我盯着点，看下载完了没有，完了就叫我一声，好让我执行XXX函数。我们今天要做的，就是构造这样一个管理器。
实现
注意，下面的代码依赖于之前所讲到的单例模式。
我们不防把上面这样一件工作成为一个计数器——Timer（这个名字可能不太恰当），把需要被通知者成为观察者——Oberver，而像下载管理器这样的对象成为一个主题——Subject。
首先，我们来定义观察者和主题对象。TimerObserverOrSubject.cs如下：
using UnityEngine;
using System.Collections;
public class TimerObserverOrSubject : MonoBehaviour ｛
virtual protected void OnDestroy ()
｛
if(Singleton.IsCreatedInstance("TimerController"))
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(Singleton.getInstance("TimerController") as TimerController).ClearTimer(this);
｝
｝
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TimerObserverOrSubject.cs的内容非常简单，它的工作就是在该脚本被析构时，及时地从计数器管理器里面删除涉及这个对象的所有Timer。
计数器管理器的脚本——TimerController.cs如下：
using UnityEngine; using System.Collections; using System.Collections.Generic; public class TimerController : MonoBehaviour ｛ public delegate void OnCallBack(object arg); public delegate bool OnIsCanDo(object arg); public class Timer ｛ public TimerObserverOrSubject m_Observer; public OnCallBack m_Callback = null; public object m_Arg = null; public TimerObserverOrSubject m_Subject; public OnIsCanDo m_IsCanDoFunc = null; public object m_ArgForIsCanDoFunc = null; public float m_PassTime = 0; public Timer(TimerObserverOrSubject observer, OnCallBack callback, object arg, TimerObserverOrSubject subject, OnIsCanDo isCanDoFunc, object argForIsCanDo) ｛ m_Observer = observer; m_Callback = callback; m_Arg = arg; m_Subject = subject; m_IsCanDoFunc = isCanDoFunc; m_ArgForIsCanDoFunc = argForIsCanDo; m_PassTime = 0; ｝ public Timer(TimerObserverOrSubject observer, OnCallBack callback, object arg, float time) ｛ m_Observer = observer; m_Callback = callback; m_Arg = arg; m_Subject = null; m_IsCanDoFunc = null; m_ArgForIsCanDoFunc = null; m_PassTime = time; ｝ ｝ private List<Timer> m_Timers = new List<Timer>(); private List<Timer> m_NeedRemoveTimer = new List<Timer>(); private List<Timer> m_CurRunTimer = new List<Timer>(); /// <summary> /// Sets the timer. /// </summary> /// <param name='observer'> /// The TimerObserverOrSubject you need to listen /// </param> /// <param name='callback'> /// The callback when condition is true. /// </param> /// <param name='arg'> /// Argument of the callback. /// </param> /// <param name='observer'> /// The TimerObserverOrSubject you need to observe /// </param> /// <param name='isCanDoFunc'> /// The condition function, must return a boolean. /// </param> /// <param name='argForIsCanDo'> /// Argument for condition function. /// </param> public void SetTimer(TimerObserverOrSubject observer, OnCallBack callback ,object arg, TimerObserverOrSubject subject, OnIsCanDo isCanDoFunc,object argForIsCanDo) ｛ if (observer == null || subject == null || callback == null || isCanDoFunc == null) return; if (isCanDoFunc(argForIsCanDo)) ｛ callback(arg); return; ｝ Timer timer = new Timer(observer, callback, arg, subject, isCanDoFunc, argForIsCanDo); m_Timers.Add(timer); ｝ /// <summary> /// Sets the timer. /// </summary> /// <param name='observer'> /// The TimerObserverOrSubject you need to listen /// </param> /// <param name='callback'> /// The callback when time is up. /// </param> /// <param name='arg'> /// Argument of the callback. /// </param> /// <param name='timepass'> /// Timepass before calling the callback. /// </param> public void SetTimer(TimerObserverOrSubject observer, OnCallBack callback , object arg, float timepass) ｛ if (observer != null && callback != null) ｛ Timer timer = new Timer(observer, callback, arg, timepass); m_Timers.Add(timer); ｝ ｝ /// <summary> /// Clears all Timers of the observer. /// </summary> /// <param name='observer'> /// The TimerObserverOrSubject you need to clear /// </param> public void ClearTimer(TimerObserverOrSubject observer) ｛ List<Timer> needRemovedTimers = new List<Timer>(); foreach (Timer timer in m_Timers) ｛ if (timer.m_Observer == observer || timer.m_Subject) ｛ needRemovedTimers.Add(timer); ｝ ｝ foreach (Timer timer in needRemovedTimers) ｛ m_Timers.Remove(timer); ｝ ｝ // Update is called once per frame void Update () ｛ InitialCurTimerDict(); RunTimer(); RemoveTimer(); ｝ private void InitialCurTimerDict() ｛ m_CurRunTimer.Clear(); foreach (Timer timer in m_Timers) ｛ m_CurRunTimer.Add(timer); ｝ ｝ private void RunTimer() ｛ m_NeedRemoveTimer.Clear(); foreach (Timer timer in m_CurRunTimer) ｛ if (timer.m_IsCanDoFunc == null) ｛ timer.m_PassTime = timer.m_PassTime - Time.deltaTime; if (timer.m_PassTime < 0) ｛ timer.m_Callback(timer.m_Arg); m_NeedRemoveTimer.Add(timer); ｝ ｝ else ｛ if (timer.m_IsCanDoFunc(timer.m_ArgForIsCanDoFunc)) ｛ timer.m_Callback(timer.m_Arg); m_NeedRemoveTimer.Add(timer); ｝ ｝ ｝ ｝ private void RemoveTimer() ｛ foreach (Timer timer in m_NeedRemoveTimer) ｛ if (m_Timers.Contains(timer)) ｛ m_Timers.Remove(timer); ｝ ｝ ｝ ｝
首先，它定义了回调函数的类型：
public delegate void OnCallBack(object arg); public delegate bool OnIsCanDo(object arg);
关于C#的委托机制，如果有童鞋不了解，请详见官方文档。简单来说，委托类似一个函数指针，常被用于回调函数。
然后，定义了一个数据类型Timer用于保存一个计数器的各个信息。
接下来，就是TimerController的两个重要的SetTimer函数。我们先看第一个SetTimer函数：
/// <summary> /// Sets the timer. /// </summary> /// <param name='observer'> /// The observer to observe the subject /// </param> /// <param name='callback'> /// The callback when condition is true. /// </param> /// <param name='arg'> /// Argument of the callback. /// </param> /// <param name='subject'> /// The subject you need to observe /// </param> /// <param name='isCanDoFunc'> /// The condition function, must return a boolean. /// </param> /// <param name='argForIsCanDo'> /// Argument for condition function. /// </param> public void SetTimer(TimerObserverOrSubject observer, OnCallBack callback ,object arg, TimerObserverOrSubject subject, OnIsCanDo isCanDoFunc,object argForIsCanDo) ｛ if (observer == null || subject == null || callback == null || isCanDoFunc == null) return; if (isCanDoFunc(argForIsCanDo)) ｛ callback(arg); return; ｝ Timer timer = new Timer(observer, callback, arg, subject, isCanDoFunc, argForIsCanDo); m_Timers.Add(timer); ｝
根据函数说明可以看出，它负责建立一个计数器，当subject的isCanDoFunc(argForIsCanDo)函数返回true时，通知observer，执行observer的callback(arg)函数。
第二个SetTimer函数更简单：
/// <summary> /// Sets the timer. /// </summary> /// <param name='observer'> /// The observer to observe the subject /// </param> /// <param name='callback'> /// The callback when time is up. /// </param> /// <param name='arg'> /// Argument of the callback. /// </param> /// <param name='timepass'> /// Timepass before calling the callback. /// </param> public void SetTimer(TimerObserverOrSubject observer, OnCallBack callback , object arg, float timepass) ｛ if (observer != null && callback != null) ｛ Timer timer = new Timer(observer, callback, arg, timepass); m_Timers.Add(timer); ｝ ｝
它负责建立一个计数器，在timepass的时间后，通知observer，执行observer的callback(arg)函数。
Update()函数里面负责检查所有Timer是否可以触发以及是否需要删除。
例子
在这个例子里，我们需要在程序开始运行5秒后，打印一些信息。当然这个的实现有很多方法，这里我们使用今天实现的TimerController来实现。
TimerSample.cs的内容如下：
using UnityEngine;
using System.Collections;
public class TimerSample : TimerObserverOrSubject ｛
private TimerController m_TimerCtr = null;
private bool m_IsCanDisplay = false;
private string m_DisplayContent = "Hello, candycat!";
// Use this for initialization
void Start () ｛
m_TimerCtr = Singleton.getInstance("TimerController") as TimerController;
//m_TimerCtr.SetTimer(this, Display, m_DisplayContent, 5);
m_TimerCtr.SetTimer(this, Display, null, this, IsCanDisplay, null);
StartCoroutine(DelayDisplay());
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void Display(object arg) ｛
if (arg == null) ｛
Debug.Log(m_DisplayContent);
｝ else ｛
string content = arg as string;
Debug.Log(content);
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bool IsCanDisplay(object arg) ｛
return m_IsCanDisplay;
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IEnumerator DelayDisplay() ｛
yield return new WaitForSeconds(5.0f);
m_IsCanDisplay = true;
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// Update is called once per frame
void Update () ｛
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首先，它向TimerController请求注册了一个计时器。这里，它的条件是IsCanDisplay函数，它返回bool值m_IsCanDisplay。而这个值将会在5秒后，通过协同函数DelayDisplay来由false置为true。当其为true时，TimerController就将通知TimerSample调用Display函数。
我们将第16行代码注释解开，并将18-20行代码注释掉，则可以达到相同的效果。
结束语
C#的委托机制还是非常常用的，使用Unity的童鞋最好还是了解一下。关于TimerController的执行效率，由于它是每一帧都要去判断所有的condition函数，所以应当让condition函数中的逻辑尽可能简单。
来自：http://www.unity.5helpyou.com/2826.html