Unity3D開發（三）：情境管理外掛程式Scene Manager

1.使用一個棧來儲存玩家在遊戲中情境的載入先後關係（方便Back功能實現以及記錄當前情境ID）

2.提供切換情境，壓棧情境，出棧情境方法

3.提供非同步載入情境，並提供載入進度（用以顯示Loading條）

 DoTransition()，代碼如下：

protected virtual IEnumerator DoTransition() {// 第一部分：之前情境退齣動畫state = SMTransitionState.Out;Prepare();float time = 0;while(Process(time)) {time += Time.deltaTime;// wait for the next frameyield return 0;}// wait another frame...yield return 0;// 第二部分：保證SMTransition對象不被銷毀（完成後續動畫）state = SMTransitionState.Hold;DontDestroyOnLoad(gameObject);// wait another frame...yield return 0;IEnumerator loadLevel = DoLoadLevel();while (loadLevel.MoveNext()) {yield return loadLevel.Current;} // wait another frame...yield return 0;// 第三部分：新情境載入動畫state = SMTransitionState.In;Prepare();time = 0;while(Process(time)) {time += Time.deltaTime;// wait for the next frameyield return 0;}// wait another frame...yield return 0;Destroy(gameObject);}

在SMTransition的子類中，分別實現Prepare()虛方法和Process(float elapsedTime)抽象方法

protected override bool Process(float elapsedTime) {float effectTime = elapsedTime;// invert direction if necessaryif (state == SMTransitionState.In) {effectTime = duration - effectTime;}progress = SMTransitionUtils.SmoothProgress(0, duration, effectTime);return elapsedTime < duration;}

public void OnGUI() {GUI.depth = 0;Color c = GUI.color;GUI.color = new Color(1, 1, 1, progress);GUI.DrawTexture(new Rect(0, 0, Screen.width, Screen.height), overlayTexture);GUI.color = c;}

其它SMTransition子類也通過Process(float elapsedTime)實現切換動畫效果！

PS: 在非同步載入情境中，Scene Manager中並沒有提供一個擷取當前載入進度的介面，需要自己實現，在SMTransition類中

protected virtual YieldInstruction LoadLevel() {if (loadAsync) {            AsyncOperation ao = Application.LoadLevelAsync(screenId);            Debug.Log("Progress: " + ao.progress);            return ao;            //return Application.LoadLevelAsync(screenId);} else {Application.LoadLevel(screenId);return null;}}