Unity5.X打包与加载AssetBundle

所有脚本代码来自官方

打包AssetBundle:

在Editor界面，点击prefab或文件，在AssetsBundle处设置此prefab的Assetsbundles属性。
点New可以创建AssetBundle名称，输入“/”可设置下一级名称。
多个物体可设为同一个AssetBundle名称。

添加一个脚本，给Editor增加一个打包的功能：

using UnityEditor;

public class CreateAssetBundles
{
    [MenuItem ("Assets/Build AssetBundles")]
    static void BuildAllAssetBundles ()
    {
        BuildPipeline.BuildAssetBundles ("Assets/AssetBundles", BuildAssetBundleOptions.None, BuildTarget.StandaloneOSXUniversal);
    }
}

其中”AssetBundles”为需要手工添加的文件夹名称。

在顶部Assets目录中的底部会出现Build Assetbundles选项。点击后会开始build进程。

AssetBundles目录中会出现一个AssetBundles文件（作用未知）和一个AssetBundles.manifest文件，manifest文件里写明了各AssetBundles的关系。

如果之前设置的Assetbundle属性有多个层级，则AssetBundles文件夹中会出现相应的下一级文件夹，AssetBundle文件以及它对应的manifest文件。

加载AssetBundle：

有两种方式
1，下载但不储存到缓存中

using System;
using UnityEngine;
using System.Collections; class NonCachingLoadExample : MonoBehaviour {
    public string BundleURL;
    public string AssetName;
    IEnumerator Start() {
        // Download the file from the URL. It will not be saved in the Cache
        using (WWW www = new WWW(BundleURL)) {
            yield return www;
            if (www.error != null)
                throw new Exception("WWW download had an error:" + www.error);
            AssetBundle bundle = www.assetBundle;
            if (AssetName == "")
                Instantiate(bundle.mainAsset);
            else
                Instantiate(bundle.LoadAsset(AssetName));
            // Unload the AssetBundles compressed contents to conserve memory
            bundle.Unload(false);

        } // memory is freed from the web stream (www.Dispose() gets called implicitly)
    }
}

2，下载并储存到缓存中（推荐）

using System;
using UnityEngine;
using System.Collections;

public class CachingLoadExample : MonoBehaviour {
    public string BundleURL;
    public string AssetName;
    public int version;

    void Start() {
        BundleURL="file://"+Application.dataPath+BundleURL;
        StartCoroutine (DownloadAndCache());
    }

    IEnumerator DownloadAndCache (){
        // Wait for the Caching system to be ready
        while (!Caching.ready)
            yield return null;

        // Load the AssetBundle file from Cache if it exists with the same version or download and store it in the cache
        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;
            if (AssetName == "")
                Instantiate(bundle.mainAsset);
            else
//              Instantiate(bundle.mainAsset);

//              Instantiate(bundle.LoadAsset(AssetName));
                foreach(UnityEngine.Object temp in bundle.LoadAllAssets())
                {
                    Instantiate(temp);
                }
    //      Instantiate(bundle.LoadAllAssets());
            // Unload the AssetBundles compressed contents to conserve memory
            bundle.Unload(false);

        } // memory is freed from the web stream (www.Dispose() gets called implicitly)
    }
}

加载脚本中两个变量的说明：
-变量BundleURL的格式：
–如果为UnityEditor本地：
—“file://”+“application.datapath”+“/文件夹名称/文件名”
–如果为服务器：
—http://….

-变量AssetName:
–为prefab或文件的名字。

如果要同时实例化所有AssetBundle中的物体（如果都是prefab)，可用LoadAllAssets()方法，例如：

foreach(UnityEngine.Object temp in bundle.LoadAllAssets())
{
    Instantiate(temp);
}

这样，之前被打包进AssetBundle内的prefab就会出现在场景中了。