AssetBundle的基礎使用

一、關於AssetBundle

1.什麼是AssetBundle

1) AssetBundle是一種經過Unity引擎處理了的資源包

2) 已經序列化的資源

3) 具有針對平臺的特性

4) 外部不相干,使用同樣加密方式的包，可以互相調用

2.類型

1) 一個場景打成一個AB包，使用的時候，是將場景加載到遊戲中

2) 鬆散資源包，一堆可複用的資源打成一個包，使用的時候，是按需載入包

3.作用

1) 最小化APP安裝包

1) 增量更新

3) 更好的控制實時的內存消耗

4) 選擇性的提供不同的內容

5) 減少打包和迭代時間

二、打包AssetBundle

打包方法：  BuildPipeline.BuildAssetBundles()

我們看到BuildAssetBundles() unity提供了兩種重載方法，先來說第一種

public static AssetBundleManifest BuildAssetBundles(string outputPath, BuildAssetBundleOptions assetBundleOptions, BuildTarget targetPlatform);

這裏有三個參數，第一個是輸出路徑，第二個打包的配置選項（一般選壓縮格式），第三個是打包的目標平臺

注：assetbundle的壓縮格式有3中：

1）LZMA --> BuildAssetBundleOptions.None    包最小，加載最慢

2）LZ4 --> BuildAssetBundleOptions.ChunkBasedCompression    包比不壓縮小，加載比不壓縮略慢

1）不壓縮 --> BuildAssetBundleOptions.UncompressedAssetBundle    包最大，加載最快

這種方法主要是根據我們在Inspector面板中對物體設置的assetbundle名進行打包，比如

擴展編輯器的打包代碼，Directory.CreateDirectory(savePath); 把文件保存在asset的同級目錄。

using UnityEditor;
using System.IO;

public class BuildAssetBundle : Editor
{
    private static string savePath = "AssetBundles";

    [MenuItem("Tools/BuildAssetBundle")]
    public static void BuildAssetBunlde()
    {
        if (Directory.Exists(savePath) == false)
        {
            Directory.CreateDirectory(savePath);
        }
        BuildPipeline.BuildAssetBundles(savePath, BuildAssetBundleOptions.None, BuildTarget.StandaloneWindows64);
        AssetDatabase.Refresh();
    }
}

還有根據路徑打包

public static AssetBundleManifest BuildAssetBundles(string outputPath, AssetBundleBuild[] builds, BuildAssetBundleOptions assetBundleOptions, BuildTarget targetPlatform);

這個方法多了一個參數AssetBundleBuild[] builds

我們可以看到是Unity封裝的一個打包結構體

必須設置assetBundleName和assetNames，其它可設可不設

assetBundleName即爲打出的assetbundle名

assetNames爲你要打包的資源路徑，這裏使用相對路徑，它是一個數組，說明可以把多個對象打成一個assetbundle。

第二種打包方法代碼

 

        if (Directory.Exists(savePath) == false)
        {
            Directory.CreateDirectory(savePath);
        }

        List<AssetBundleBuild> builds = new List<AssetBundleBuild>();
        
        AssetBundleBuild build = new AssetBundleBuild();
        build.assetBundleName = "Micro_Wizard.unity3d";
        build.assetNames = new string[] { "Assets/Toon/Micro_Wizard.prefab" };
        builds.Add(build);

        BuildPipeline.BuildAssetBundles(savePath, builds.ToArray(), BuildAssetBundleOptions.None, BuildTarget.StandaloneWindows64);
        AssetDatabase.Refresh();

三、加載AssetBundle

1.從本地文件中加載

    public void LoadFromFile()
    {
        AssetBundle assetBundle = AssetBundle.LoadFromFile(Application.dataPath + "/../AssetBundles/Micro_Wizard.unity3d");
        Instantiate(assetBundle.LoadAsset<GameObject>("Micro_Wizard.prefab"));
    }

2.從內存中加載

    public void LoadFromMemory()
    {
        AssetBundle assetBundle = AssetBundle.LoadFromMemory(File.ReadAllBytes(Application.dataPath + "/../AssetBundles/Micro_Wizard.unity3d"));
        Instantiate(assetBundle.LoadAsset<GameObject>("Micro_Wizard.prefab"));
    }

3.從文件流加載

    public void LoadFromStream()
    {
        var fileStream = new FileStream(Application.dataPath + "/../AssetBundles/Micro_Wizard.unity3d", FileMode.Open, FileAccess.Read);
        AssetBundle assetBundle = AssetBundle.LoadFromStream(fileStream);
        Instantiate(assetBundle.LoadAsset<GameObject>("Micro_Wizard.prefab"));
    }

4.UnityWebRequest加載

    public void WebRequest()
    {
        StartCoroutine(WaitWebRequest());
    }

    IEnumerator WaitWebRequest()
    {
        UnityWebRequest request = UnityWebRequestAssetBundle.GetAssetBundle(Application.dataPath + "/../AssetBundles/Micro_Wizard.unity3d");   
        yield return request.SendWebRequest();
        //AssetBundle assetBundle = DownloadHandlerAssetBundle.GetContent(request);
        AssetBundle assetBundle = (request.downloadHandler as DownloadHandlerAssetBundle).assetBundle;
        Instantiate(assetBundle.LoadAsset<GameObject>("Micro_Wizard.prefab"));
    }

5.WWW加載

注：從2018版本後，這個方法已過時，使用UnityWebRequest方法代替

    public void WWWLoad()
    {
        StartCoroutine(WaitWWWLoad());
    }

    IEnumerator WaitWWWLoad()
    {
        while (Caching.ready == false)
            yield return null;

        WWW www = WWW.LoadFromCacheOrDownload(Application.dataPath + "/../AssetBundles/Micro_Wizard.unity3d", 1);
        yield return www;

        if (!string.IsNullOrEmpty(www.error))
        {
            Debug.Log(www.error);
            yield break;
        }
        AssetBundle assetBundle = www.assetBundle;
        Instantiate(assetBundle.LoadAsset<GameObject>("Micro_Wizard.prefab"));
    }