unity的异步加载

注意点

AsyncOperation的progress（0-1）属性在isDone为false时，最大加载到0.9就会暂停，直到isDone为true时才会继续加载0.9-1.0的这10%，而isDone为true或fasle的标志为是： 当allowSceneActivation = false，isDone为false ，allowSceneActivation = false 的作用是让场景不会在加载完成后自动跳转到下一个场景，   当allowSceneActivation = true，isDone为true，或者progress = 1.0时 isDone = true

示例

（1）代码（没有用到isDone）

 public Slider progressUI; //进度条
    public Text progressValue; //百分比描述文本
    private AsyncOperation prog;  // 异步操作类
    void Start()
    {
        StartCoroutine(LoadAsycLevel()); //启动协同
    }
    // 设置进度条值
    private void SetProgressValue(int value)
    {
        progressUI.value = value;
        progressValue.text =value + "%";
    }
 
    // 异步加载场景
    IEnumerator LoadAsycLevel()
    {
        //异步加载场景
         prog = SceneManager.LoadSceneAsync("CG");
        //如果加载完成，也不进入场景
        prog.allowSceneActivation = false;
        //最终的进度
        int toProgress = 0;
        //显示的进度
        int showProgress = 0;
        //测试了一下，进度最大就是0.9
        while (prog.progress < 0.9f)
        {
            //toProcess具有随机性
            toProgress = (int)(prog.progress * 100);
            while (showProgress < toProgress)
            {
                showProgress++;
                SetProgressValue(showProgress);
                yield return new WaitForEndOfFrame(); //等待一帧
            }
        }
        toProgress = 100;
 
        while (showProgress < toProgress)
        {
            showProgress++;
            SetProgressValue(showProgress);
            yield return new WaitForEndOfFrame(); //等待一帧
        }
        prog.allowSceneActivation = true;  //如果加载完成，可以进入场景
    }

（2）代码（用到isDone）

 private Text progress;
    //进度条的数值
    private float progressValue;
    //进度条
    private Slider slider;
    [Tooltip("下个场景的名字")]
    public string nextSceneName;
   //创建异步加载类
    private AsyncOperation async = null;
 
    private void Start() {
        progress = GetComponent<Text>();
        slider = FindObjectOfType<Slider>();
   //启用协程 
        StartCoroutine("LoadScene");
    }
 
    IEnumerator LoadScene() {
        async = SceneManager.LoadSceneAsync(nextSceneName);
        //即使加载完也不跳场景
        async.allowSceneActivation = false;
        while (!async.isDone) {
            if (async.progress < 0.9f)
                progressValue = async.progress;
            else
                progressValue = 1.0f;
 
            slider.value = progressValue;
            progress.text = (int)(slider.value * 100) + " %";
 
            if (progressValue >= 0.9) {
                progress.text = "按任意键继续";
                if (Input.anyKeyDown) {
                    async.allowSceneActivation = true;
                }
            }
            yield return null;
        }
    }