初探AssetBundle

首先来说说神马是AssetBundle，AssetBundle其实就是一个存在于硬盘中的文件或者说是一个压缩包。

其次来说说AssetBundle的工作流程，其实AssetBundle的工作流程看下面两张图就大概能理解了。

首先，（苦逼的程序员）将资源打包成AssetBundle包，然后将AssetBundle包上传到服务器，游戏玩家在进入游戏发现有更新时，从服务器上下载Asset Bundle包完成更新。

接下来就进入正题了，怎样将资源打包成AssetBundle包呢？

首先创建一个unity3d项目，然后创建一个物体（如一个Cube），将这个Cube制作成一个Prefab，点击这个Prefab，在unity的右下角就会出现这样的一个东东：

前面是AssetBundle的名字，后面是后缀，后缀以任何形式都可以。然后创建一个C#脚本，脚本必须放在Editor文件夹中（在Assets目录下创建一个就好了），将这段代码copy进去

[MenuItem("Assets/Build AssetBundles")]    static void BuildAllAssetBundles()    {        string dir = "AssetBundles";        if(Directory.Exists(dir)==false)        {            Directory.CreateDirectory(dir);        }        BuildPipeline.BuildAssetBundles(dir, BuildAssetBundleOptions.None, BuildTarget.StandaloneWindows);    }

注意，类里面只放这段代码，而且类不需要继承MonoBehaviour，命名空间只需引入UnityEditor，保存后回到unity中，点击左上角的Assets就会出现刚刚代码添加的Build AssetBundle。点击Build AssetBundle unity就会自动打包添加了AssetBundle标签的资源。打包完成后，找到AssetBundles目录，点开就会发现里面多了些东西，这些东西当然就是刚刚打包进来的东西咯

接下来说说怎样加载本地的Asset Bundle包和包里的资源：

一：从内存中进行加载：LoadFromMemory（同步），LoadFromMemoryAsync（异步）

（1） LoadFromMemory:

        string sharepath = "AssetBundles/share.unity3d";        string wallpath = "AssetBundles/cubewall.unity3d";        AssetBundle share = AssetBundle.LoadFromMemory(File.ReadAllBytes(sharepath));        AssetBundle wall = AssetBundle.LoadFromMemory(File.ReadAllBytes(wallpath));        GameObject wallPrefab = wall.LoadAsset<GameObject>("CubeWall");        Instantiate(wallPrefab);

（2） LoadFromMemoryAsync: （返回值为IEnumerator)

        string sharepath = "AssetBundles/share.unity3d";        string wallpath = "AssetBundles/cubewall.unity3d";        AssetBundleCreateRequest share = AssetBundle.LoadFromMemoryAsync(File.ReadAllBytes(sharepath));        AssetBundleCreateRequest wall = AssetBundle.LoadFromMemoryAsync(File.ReadAllBytes(wallpath));        yield return wall;        AssetBundle shareAB = share.assetBundle;        AssetBundle wallAB = wall.assetBundle;        GameObject wallPrefab = wallAB.LoadAsset<GameObject>("CubeWall");        Instantiate(wallPrefab);

二：从本地进行读取：LoadFromFile（同步）, LoadFromFileAsync（异步）

（1）LoadFromFile:

        string sharepath = "AssetBundles/share.unity3d";        string wallpath = "AssetBundles/cubewall.unity3d";        AssetBundle share = AssetBundle.LoadFromFile(sharepath);        AssetBundle wall = AssetBundle.LoadFromFile(wallpath);        GameObject wallPrefab = wall.LoadAsset<GameObject>("CubeWall");        Instantiate(wallPrefab);

（二）LoadFromFileAsync:（返回值为IEnumerator）

        string sharepath = "AssetBundles/share.unity3d";        string wallpath = "AssetBundles/cubewall.unity3d";        AssetBundleCreateRequest share = AssetBundle.LoadFromFileAsync(sharepath);        AssetBundleCreateRequest wall = AssetBundle.LoadFromFileAsync(wallpath);        yield return wall;        AssetBundle shareAB = share.assetBundle;        AssetBundle wallAB = wall.assetBundle;        GameObject wallPrefab = wallAB.LoadAsset<GameObject>("CubeWall");        Instantiate(wallPrefab);

三： 以WWW的方式进行读取：WWW.LoadFromCacheorDownload（返回值为IEnumerator）

        string uri = @"file:///F:\unity3D\assertBundleLearning\AssetBundles\share.unity3d";        string uri2 = @"file:///F:\unity3D\assertBundleLearning\AssetBundles\cubewall.unity3d";        while (Caching.ready == false)        {            yield return null;        }        WWW www = WWW.LoadFromCacheOrDownload(uri, 1);        yield return www;        if (string.IsNullOrEmpty(www.error) == false)        {            Debug.Log(www.error);            yield break;        }        AssetBundle share = www.assetBundle;        www = WWW.LoadFromCacheOrDownload(uri2, 1);        yield return www;        if (string.IsNullOrEmpty(www.error) == false)        {            Debug.Log(www.error);            yield break;        }        AssetBundle wall = www.assetBundle;        GameObject wallPrefab = wall.LoadAsset<GameObject>("CubeWall");        Instantiate(wallPrefab);

四： 使用UnityWebRequest来进行读取（返回值为IEnumerator）

        string uri = @"file:///F:\unity3D\assertBundleLearning\AssetBundles\cubewall.unity3d";        UnityWebRequest wall = UnityWebRequest.GetAssetBundle(uri);        yield return wall.Send();        AssetBundle wallAB = DownloadHandlerAssetBundle.GetContent(wall);        // 或 AssetBundle wallAB = wall.downloadHandler as DownloadHandlerAssetBundle). assetBundle;        GameObject wallPrefab = wallAB.LoadAsset<GameObject>("CubeWall");        Instantiate(wallPrefab);        AssetBundle manifestAB = AssetBundle.LoadFromFile("AssetBundles/AssetBundles");        AssetBundleManifest manifest = manifestAB.LoadAsset<AssetBundleManifest>("AssetBundleManifest");        string[] strs = manifest.GetDirectDependencies("CubeWall.unity3d");        foreach (string name in strs)        {            AssetBundle.LoadFromFile("AssetBundles/" + name);        }

好了，AssetBundle的加载暂时就降到这里，剩下的没讲到的下次在继续将了，拜拜。