unity5.X AB包打包插件研究

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AssetBundleManager中的Update方法，是程序前进的推动者，因为update方法是逐帧执行，时刻的都在观察执行

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    void Update()
    {
        var keysToRemove = new List<string>();
        //检查所有正在下载的WWW，是否已经下载完毕
        foreach (var keyValue in m_DownloadingWWWs)
        {
            WWW download = keyValue.Value;

            if (download.error != null)
            {
                m_DownloadingErrors.Add(keyValue.Key, download.error);
                keysToRemove.Add(keyValue.Key);
                continue;
            }
            // 如下载完成，进行封装保存到字典中
            if(download.isDone)
            {
                //Debug.Log("Downloading " + keyValue.Key + " is done at frame " + Time.frameCount);
                m_LoadedAssetBundles.Add(keyValue.Key, new LoadedAssetBundle(download.assetBundle) );
                keysToRemove.Add(keyValue.Key);
            }
        }

        // 从字典中移除已经下载完成的WWW，并且对WWW进行释放
        foreach( var key in keysToRemove)
        {
            WWW download = m_DownloadingWWWs[key];
            m_DownloadingWWWs.Remove(key);
            download.Dispose();
        }

        // 检查是否可以从AB包中下载资源
        for (int i=0;iif (!m_InProgressOperations[i].Update())
            {
                //处理完就移掉
                m_InProgressOperations.RemoveAt(i);
            }
            else
            {
                //当前暂不处理，接着处理下一个
                i++;
            }
        }
    }

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上面代码中这行代码m_InProgressOperations[i].Update()

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其中Update 里面代码： 就是看 AB包是不是已经下载完成，如果下载完成，就开始异步加载AB包中的资源（asset）

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public class AssetBundleLoadAssetOperationFull : AssetBundleLoadAssetOperation
{
    protected string                m_AssetBundleName;
    protected string                m_AssetName;
    protected string                m_DownloadingError;
    protected System.Type           m_Type;
    protected AssetBundleRequest    m_Request = null;

    public AssetBundleLoadAssetOperationFull (string bundleName, string assetName, System.Type type)
    {
        m_AssetBundleName = bundleName;
        m_AssetName = assetName;
        m_Type = type;
    }

    public override T GetAsset()
    {
        if (m_Request != null && m_Request.isDone)
            return m_Request.asset as T;
        else
            return null;
    }

    public override bool Update ()
    {

        if (m_Request != null)
            return false;

        LoadedAssetBundle bundle = AssetBundleManager.GetLoadedAssetBundle (m_AssetBundleName, out m_DownloadingError);
        if (bundle != null)
        {
            m_Request = bundle.m_AssetBundle.LoadAssetAsync (m_AssetName, m_Type);
            return false;
        }
        else
        {
            Debug.Log("说明还在下AssetBundle");
            return true;
        }
    }

    public override bool IsDone ()
    {
        if (m_Request == null && m_DownloadingError != null)
        {
            Debug.LogError(m_DownloadingError);
            return true;
        }

        return m_Request != null && m_Request.isDone;
    }
}

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总体思想：

WWW下载，并将WWW对象保存字典
WWW下载完成，取出Assetbundle，封装到LoadedAssetBundle对象中，将封装对象保存字典中
开始异步加载AseetBundle中的asset
记载完成后，开始实例化

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FR:海涛高软（QQ技术交流群：386476712）