【Unity】中如何統(tǒng)一管理回調(diào)函數(shù)（利用觀察者模式）

2019-11-09 14:34:57

字體：大中小

供稿：網(wǎng)友

這次的內(nèi)容有點(diǎn)類似設(shè)計(jì)模式里的觀察者模式。但是和常規(guī)意義上的觀察者模式也不是完全一致，所以各位就不要咬文嚼字啦！咦？設(shè)計(jì)模式？！不懂！沒關(guān)系，說不定你以前就用過。

開場白

我們來想象一個場景。在加載一個模型時，你需要從網(wǎng)上下載，但是你并不知道下載需要花費(fèi)多少時間。你所知道的是，當(dāng)下載完成后，就可以把模型放在特定位置上，開始游戲。那么，我們怎樣才能判斷下載完成呢？一個簡單的方法是，在每一幀的時候都判斷下載是否完成，完成后就可以繼續(xù)后面的工作。因此，我們可以這樣做，我們告訴一個管理器，嗨，你幫我盯著點(diǎn)，看下載完了沒有，完了就叫我一聲，好讓我執(zhí)行XXX函數(shù)。我們今天要做的，就是構(gòu)造這樣一個管理器。

實(shí)現(xiàn)

注意，下面的代碼依賴于之前所講到的單例模式。我們不防把上面這樣一件工作成為一個計(jì)數(shù)器——Timer（這個名字可能不太恰當(dāng)），把需要被通知者成為觀察者——Oberver，而像下載管理器這樣的對象成為一個主題——Subject。首先，我們來定義觀察者和主題對象。TimerObserverOrSubject.cs如下：[csharp] view plain copy PRint?using UnityEngine; using System.Collections; public class TimerObserverOrSubject : MonoBehaviour { virtual protected void OnDestroy () { if(Singleton.IsCreatedInstance("TimerController")) { (Singleton.getInstance("TimerController") as TimerController).ClearTimer(this); } } } TimerObserverOrSubject.cs的內(nèi)容非常簡單，它的工作就是在該腳本被析構(gòu)時，及時地從計(jì)數(shù)器管理器里面刪除涉及這個對象的所有Timer。計(jì)數(shù)器管理器的腳本——TimerController.cs如下：[csharp] view plain copy print?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，它定義了回調(diào)函數(shù)的類型：[csharp] view plain copy print?public delegate void OnCallBack(object arg); public delegate bool OnIsCanDo(object arg); 關(guān)于C#的委托機(jī)制，如果有童鞋不了解，請?jiān)斠姽俜轿臋n。簡單來說，委托類似一個函數(shù)指針，常被用于回調(diào)函數(shù)。然后，定義了一個數(shù)據(jù)類型Timer用于保存一個計(jì)數(shù)器的各個信息。接下來，就是TimerController的兩個重要的SetTimer函數(shù)。我們先看第一個SetTimer函數(shù)：[csharp] view plain copy print?/// <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); } 根據(jù)函數(shù)說明可以看出，它負(fù)責(zé)建立一個計(jì)數(shù)器，當(dāng)subject的isCanDoFunc(argForIsCanDo)函數(shù)返回true時，通知observer，執(zhí)行observer的callback(arg)函數(shù)。第二個SetTimer函數(shù)更簡單：[csharp] view plain copy print?/// <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); } } 它負(fù)責(zé)建立一個計(jì)數(shù)器，在timepass的時間后，通知observer，執(zhí)行observer的callback(arg)函數(shù)。Update()函數(shù)里面負(fù)責(zé)檢查所有Timer是否可以觸發(fā)以及是否需要刪除。

例子

在這個例子里，我們需要在程序開始運(yùn)行5秒后，打印一些信息。當(dāng)然這個的實(shí)現(xiàn)有很多方法，這里我們使用今天實(shí)現(xiàn)的TimerController來實(shí)現(xiàn)。TimerSample.cs的內(nèi)容如下：[csharp] view plain copy print?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()); } void Display(object arg) { if (arg == null) { Debug.Log(m_DisplayContent); } else { string content = arg as string; Debug.Log(content); } } bool IsCanDisplay(object arg) { return m_IsCanDisplay; } IEnumerator DelayDisplay() { yield return new WaitForSeconds(5.0f); m_IsCanDisplay = true; } // Update is called once per frame void Update () { } } 首先，它向TimerController請求注冊了一個計(jì)時器。這里，它的條件是IsCanDisplay函數(shù)，它返回bool值m_IsCanDisplay。而這個值將會在5秒后，通過協(xié)同函數(shù)DelayDisplay來由false置為true。當(dāng)其為true時，TimerController就將通知TimerSample調(diào)用Display函數(shù)。我們將第16行代碼注釋解開，并將18-20行代碼注釋掉，則可以達(dá)到相同的效果。

結(jié)束語

C#的委托機(jī)制還是非常常用的，使用Unity的童鞋最好還是了解一下。關(guān)于TimerController的執(zhí)行效率，由于它是每一幀都要去判斷所有的condition函數(shù)，所以應(yīng)當(dāng)讓condition函數(shù)中的邏輯盡可能簡單。好了，這次就到這里，如果有更好的想法，或者這里的代碼有什么問題，都非常歡迎指正。謝謝閱讀！

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