[Unity] unity5.3 assetbundle打包及加载

　　Unity5.3更新了assetbundle的打包和加载api，下面简单介绍使用方法及示例代码。

　　在Unity中选中一个prefab查看Inspector窗口，有两个位置可以进行assetbundle的标记。

　　第一个为assetBundleName，如果这里不是None，则这个资源会记录到AssetDatabase里，使用BuildAssetBundles打包时，会自动将AssetBundleName一致的资源打到一个包中。

　　第二个为Variant，可用于区分不同分辨率的资源。如果在abName=S的情况下，variant有None也有HD，打ab包时会报错，如果variant有指定，则同一abName的资源的variant不能为None。

     

// 此api用于打包所有标记了AssetBundleName的资源 

public static AssetBundleManifest BuildAssetBundles(

　　string outputPath,

　　BuildAssetBundleOptions assetBundleOptions = BuildAssetBundleOptions.None,

　　BuildTarget targetPlatform = BuildTarget.WebPlayer

);

// 此api用于打包指定的资源

public static AssetBundleManifest BuildAssetBundles(

　　string outputPath,

　　AssetBundleBuild[] builds, 

　　BuildAssetBundleOptions assetBundleOptions = BuildAssetBundleOptions.None, 

　　BuildTarget targetPlatform = BuildTarget.WebPlayer

);

 　　其中，AssetBundleBuild数组参数，用于指定资源，AssetBundleBuild有三个属性，分别指定assetBundleName，variant，资源路径等。

 

 

　　以下为打包及加载部分代码：大部分参考了雨凇MOMO的文章《UGUI研究院之全面理解图集与使用（三）》，做了部分修改。

#define USE_ASSETBUNDLE

using UnityEngine;
using System.Collections;
using UnityEngine.UI;
using UnityEditor.VersionControl;

public class UIMain : MonoBehaviour{

    AssetBundle assetbundle = null;
    void Start () 
    {
        CreatImage(loadSprite("flag_blue"));
        CreatImage(loadSprite("flag_yellow"));
    }

    private void CreatImage(GameObject gobj ){
        Sprite sprite = gobj.GetComponent<SpriteRenderer>().sprite as Sprite;
        GameObject go = new GameObject(sprite.name);
        go.layer = LayerMask.NameToLayer("UI");
        go.transform.parent = transform;
        go.transform.localScale= Vector3.one;
        Image image = go.AddComponent<Image>();
        image.sprite = sprite;
        image.SetNativeSize();
    }

    private GameObject loadSprite(string spriteName){
        #if USE_ASSETBUNDLE
        if(assetbundle == null)
            assetbundle = AssetBundle.LoadFromFile(Application.streamingAssetsPath +"/flagbundle");
        return assetbundle.LoadAsset(spriteName) as GameObject;
        #else
        return Resources.Load<GameObject>("Sprite/" + spriteName);
        #endif    
    }

}

using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using UnityEditor;
using System.IO;
using UnityEditor.VersionControl;

public class AltasMaker : MonoBehaviour {

    [MenuItem ("MyMenu/AtlasMaker")]
    static private void MakeAtlas()
    {
        string spriteDir = Application.dataPath + "/Resources/Sprite";
        Debug.Log("spriteDir : " + spriteDir);
        if(!Directory.Exists(spriteDir)){
            Directory.CreateDirectory(spriteDir);
        }
        
        DirectoryInfo rootDirInfo = new DirectoryInfo (Application.dataPath + "/Atlas");
        foreach (DirectoryInfo dirInfo in rootDirInfo.GetDirectories()) {
            foreach (FileInfo pngFile in dirInfo.GetFiles("*.png", SearchOption.AllDirectories)) {
                string allPath = pngFile.FullName;
                Debug.Log("allPath1 : " + allPath);
                string assetPath = allPath.Substring(allPath.IndexOf("Assets"));
                Debug.Log("assetPath : " + assetPath);
                Sprite sprite = AssetDatabase.LoadAssetAtPath<Sprite>(assetPath);
                GameObject go = new GameObject(sprite.name);
                go.AddComponent<SpriteRenderer>().sprite = sprite;
                allPath = spriteDir+ "/" +sprite.name+ ".prefab";
                Debug.Log("allPath2 : " + allPath);
                string prefabPath = allPath.Substring(allPath.IndexOf("Assets"));
                PrefabUtility.CreatePrefab(prefabPath, go);
                GameObject.DestroyImmediate(go);
            }
        }    
    }

    [MenuItem ("MyMenu/Build Assetbundle")]
    static private void BuildAssetBundle()
    {
        string outputdir = Application.dataPath + "/StreamingAssets";

        if(!Directory.Exists(outputdir))
        {
            Directory.CreateDirectory(outputdir);
        }

        DirectoryInfo rootDirInfo = new DirectoryInfo (Application.dataPath + "/Atlas");
        foreach (DirectoryInfo dirInfo in rootDirInfo.GetDirectories()) {
            List<Sprite> assets = new List<Sprite>();

            foreach (FileInfo pngFile in dirInfo.GetFiles("*.png", SearchOption.AllDirectories)) 
            {
                string allPath = pngFile.FullName;
                string assetPath = allPath.Substring(allPath.IndexOf("Assets"));
                assets.Add(AssetDatabase.LoadAssetAtPath<Sprite>(assetPath));
            }

            AssetBundleBuild[] buildMap  = new AssetBundleBuild[1];

            buildMap[0].assetBundleName = dirInfo.Name + "bundle"; // 想定义的任何名称  
            string[] spriteNames = new string[assets.Count];
            for(int i = 0; i < assets.Count; i++)
            {
                spriteNames[i] = "Assets/Atlas/" + dirInfo.Name + "/" + assets[i].name + ".png"; // 注意路径写全 
            }
            buildMap[0].assetNames = spriteNames;
            buildMap[0].assetBundleVariant = null;

            BuildPipeline.BuildAssetBundles(
                outputdir,  // output path
                buildMap,  // build bundles info
                BuildAssetBundleOptions.UncompressedAssetBundle,  // options
                GetBuildTarget()); // build target
        }    
    }

    [MenuItem ("MyMenu/Build All AssetBundles")]
    static private void BuildAllAssetBundles()
    {
        BuildPipeline.BuildAssetBundles(
            Application.dataPath + "/StreamingAssets",  // output path
            BuildAssetBundleOptions.ChunkBasedCompression,  // options
            GetBuildTarget()); 
    }

    static private BuildTarget GetBuildTarget()
    {
        BuildTarget target = BuildTarget.WebPlayer;
        #if UNITY_STANDALONE
        target = BuildTarget.StandaloneOSXIntel64;
        #elif UNITY_IPHONE
        target = BuildTarget.iPhone;
        #elif UNITY_ANDROID
        target = BuildTarget.Android;
        #endif
        return target;
    }
}

　　注：1 经过验证，同一个资源如果没有改变，不会被重新build

　　　　2 如果缓存文件不刷新，强制调用Caching.CleanCache()。 

　　assetbundle有三种压缩格式：默认为LZMA模式（最小），还有LZ4和不压缩（最大）。

　　不同压缩格式相关优缺点及使用详见下文：Unity5.x新的AssetBundle机制02——压缩

其他参考：

1 UGUI研究院之全面理解图集与使用（三）

2 【厚积薄发】揭开Unity AssetBundle庐山真面目（二）

3 Unity3D 5.3 新版AssetBundle使用方案及策略

4 AssetDatabase