AssetBundle.LoadFromMemoryAsync

AssetBundleCreateRequest LoadFromMemoryAsync(byte[] binary, uint crc = 0);
使用二进制数据异步加载ab对象，通常我们对ab进行加密后，下载到本地解密，然后将解密后的二进制数据传进来，最后获取到ab对象。
如果是LZMA压缩的AB，会在加载的过程中进行解压；如果是LZ4压缩的AB，会直接加载压缩状态的数据。
与同步版接口LoadFromMemory立即返回ab对象不同，LoadFromMemoryAsync会在后台线程中执行解压操作。
IEnumerator LoadFromMemoryAsync(string path)
    AssetBundleCreateRequest createRequest = AssetBundle.LoadFromMemoryAsync(File.ReadAllBytes(path));
    yield return createRequest;
    AssetBundle bundle = createRequest.assetBundle;
    var prefab = bundle.LoadAsset.<GameObject>("MyObject");
    Instantiate(prefab);
AssetBundle.LoadFromFile
AssetBundle LoadFromFile(string path, uint crc = 0, ulong offset = 0); 
从本地加载未压缩（uncompressed）或使用LZ4压缩的AB，效率很高。
加载LZMA压缩的AB时，会先将其解压，然后再载入内存。
在Unity5.3及之前的版本中，在Android平台下调用这个接口去加载StreamingAssets目录下的ab会失败，因为安卓下这个目录是一个.jar的压缩文件。不过Unity5.4以及之后的版本已经修复这个问题，可以正常使用。
var myLoadedAssetBundle = AssetBundle.LoadFromFile(Path.Combine(Application.streamingAssetsPath, "myassetBundle"));
if (myLoadedAssetBundle == null) {
    Debug.Log("Failed to load AssetBundle!");
    return;
var prefab = myLoadedAssetBundle.LoadAsset.<GameObject>("MyObject");
Instantiate(prefab);
WWW.LoadFromCacheOrDownload
WWW LoadFromCacheOrDownload(string url, int version);
不推荐使用此接口，因为使用www对象来存储ab对象会造成内存开销过多，WebStreaming问题。
先从本地缓存中获取ab，如果不存在或者不是最新版本，则会从远程下载。如果ab是压缩过的，则会在线程中解压ab，然后写入本地缓存中。一但ab解压完成并缓存之后的加载流程就跟AssetBundle.LoadFromFile完全一样。
version用法？？
IEnumerator Start()
    while (!Caching.ready)
        yield return null;
    var www = WWW.LoadFromCacheOrDownload("http://myserver.com/myassetBundle.unity3d", 5);
    yield return www;
    if (!string.IsNullOrEmpty(www.error))
        Debug.Log(www.error);
        yield return null;
    var myLoadedAssetBundle = www.assetBundle;
    var asset = myLoadedAssetBundle.mainAsset;
ab缓存由Caching类管理，Caching还可以用来做ab备份以及回滚。
https://docs.unity3d.com/ScriptReference/Caching.html
由于www的性能问题，使用这个接口时需要注意：
单个ab不能太大，一般建议不超过1M
在移动平台，同一时间最多下载一个ab，避免造成内存高峰
如果本地缓存没有足够空间，则会先删除最久没访问的资源；如果找不到可以删除的资源，则会跳过缓存过程，直接将文件加载到内容中，流程就跟"new WWW()"一样。
只能用此方法来访问AB，对其它类型资源不适用。
url中的'%'必须被省去。
UnityWebRequest
UnityWebRequest UnityWebRequest.GetAssetBundle(string uri, uint crc);
AssetBundle DownloadHandlerAssetBundle.GetContent(Networking.UnityWebRequest www);
最推荐的方式来替代www的方式加载AB，以减少webstream内存占用问题
先用UnityWebRequest.GetAssetBundle进行下载
再用DownloadHandlerAssetBundle.GetContent(UnityWebRequest)获取AB对象
IEnumerator InstantiateObject()
    string uri = "file:///" + Application.dataPath + "/AssetBundles/" + assetBundleName;        
    UnityEngine.Networking.UnityWebRequest request = UnityEngine.Networking.UnityWebRequest.GetAssetBundle(uri, 0);
    yield return request.Send();
    AssetBundle bundle = DownloadHandlerAssetBundle.GetContent(request);
    GameObject cube = bundle.LoadAsset<GameObject>("Cube");
    GameObject sprite = bundle.LoadAsset<GameObject>("Sprite");
    Instantiate(cube);
    Instantiate(sprite);
LoadAsset
T objectFromBundle = bundleObject.LoadAsset<T>(assetName);
GameObject gameObject = loadedAssetBundle.LoadAsset<GameObject>(assetName);
Unity.Object[] objectArray = loadedAssetBundle.LoadAllAssets();
AssetBundleRequest request = loadedAssetBundleObject.LoadAssetAsync<GameObject>(assetName);
yield return request;
var loadedAsset = request.asset;
AssetBundleRequest request = loadedAssetBundle.LoadAllAssetsAsync();
yield return request;
var loadedAssets = request.allAssets;
Load Manifests
在AB根目录，会有一个Manifest的AB文件，跟加载普通AB一样
存储了依赖关系，哈希值，AB变体等
AssetBundle assetBundle = AssetBundle.LoadFromFile(manifestFilePath);
AssetBundleManifest manifest = assetBundle.LoadAsset<AssetBundleManifest>("AssetBundleManifest");
在加载AB前，需要先加载其依赖
AssetBundle assetBundle = AssetBundle.LoadFromFile(manifestFilePath);
AssetBundleManifest manifest = assetBundle.LoadAsset<AssetBundleManifest>("AssetBundleManifest");
string[] dependencies = manifest.GetAllDependencies("assetBundle"); //Pass the name of the bundle you want the dependencies for.
foreach(string dependency in dependencies)
    AssetBundle.LoadFromFile(Path.Combine(assetBundlePath, dependency));
同一个AB只能加载一次，否则会报错，提示已经加载过