缓存方式
使用WWW.LoadFromCacheOrDownload接口。AssetBundles将保存在本地设备的Unity的缓存文件夹中。WebPlayer 有50MB的缓存上限，PC/Mac/Android/IOS应有有4 GB的缓存上限。这种方式也是加载AssetBundle推荐的方式。我们使用这种方式来实践一下。在Scripts文件夹中新建脚本：
using System;
using UnityEngine;
using System.Collections;
public class CacheBundle : MonoBehaviour
{
public static readonly string BundleURL =
#if UNITY_ANDROID
"jar:file://" + Application.dataPath + "!/assets/MyAssetBundles/shape/cube";
#elif UNITY_IPHONE
Application.dataPath + "/Raw/MyAssetBundles/shape/cube";
#elif UNITY_STANDALONE_WIN || UNITY_EDITOR
//我们将加载以前打包好的cube
"file://" + Application.dataPath + "/MyAssetBundles/shape/cube";//由于是编辑器下，我们使用这个路径。
#else
string.Empty;
#endif
//还记得吗？在cube这个AssetBundle中有两个资源，Cube1和Cube2
private string AssetName = "Cube2";
//版本号
public int version;
void Start()
{
StartCoroutine(DownloadAndCache());
}
IEnumerator DownloadAndCache()
{
// 需要等待缓存准备好
while (!Caching.ready)
yield return null;
// 有相同版本号的AssetBundle就从缓存中获取，否则下载进缓存。
using (WWW www = WWW.LoadFromCacheOrDownload(BundleURL, version))
{
yield return www;
if (www.error != null)
throw new Exception("WWW download had an error:" + www.error);
AssetBundle bundle = www.assetBundle;
GameObject cube = Instantiate(bundle.LoadAsset(AssetName)) as GameObject;
cube.transform.position = new Vector3(1.5f, 0f, 0f);
// 卸载加载完之后的AssetBundle，节省内存。
bundle.Unload(false);
} //由于使用using语法，www.Dispose将在加载完成后调用，释放内存
}
}
博主注：版本号可按天来，比如
int version;
version = DateTime.dayOfYears;
http://baizihan.me/2016/03/unity-assetbundle03/
