【Unity3D】基于AssetBundle实现资源热更新

1 前言

Unity3D 本地资源一般放在 Resources 目录下，但是 Resouces 文件夹的大小不能超过 2G，使用 AssetBundle 管理资源可以解决 Resources 文件夹受限问题。

本文代码资源见→基于AssetBundle实现资源热更新。

AssetBundle 主要用于管理资源，配合 AssetDatabase 和 AssetImporter 可以实现资源重命名，配合 BuildPipeline 可以实现资源压缩，配合 WWW 或 UnityWebRequest 可以实现加载服务器资源。下面简单介绍下相关接口：

1）AssetBundle 获取资源名，加载、卸载资源

静态方法：

// 从文件中加载AssetBundle
public static AssetBundle LoadFromFile(string path)
// 从二进制数组中加载AssetBundle
public static AssetBundle LoadFromMemory(byte[] binary)
// 从流中加载AssetBundle
public static AssetBundle LoadFromStream(Stream stream)
// 卸载所有AssetBundle
public static void UnloadAllAssetBundles(bool unloadAllObjects)
// 销毁对象
public static void Destroy(Object obj)

实例方法：

// 获取所有资源名
public string[] GetAllAssetNames()
// 判断是否包含资源
public bool Contains(string name)
// 加载资源
public Object[] LoadAllAssets()
public T[] LoadAllAssets<T>() where T : Object
public Object[] LoadAllAssets(Type type)
public Object LoadAsset(string name)
public T LoadAsset<T>(string name) where T : Object
public Object LoadAsset(string name, Type type)
// 卸载资源, unloadAllLoadedObjects为false时不卸载已从Bundle中加载出的资源
public void Unload(bool unloadAllLoadedObjects)

说明：入参 name 不区分大小写，建议使用小写，如果使用大写会自动转换为小写。

2）AssetBundleManifest 获取资源依赖

// 获取所有AssetBundles
public string[] GetAllAssetBundles()
// 获取指定assetBundleName的直接依赖
public string[] GetDirectDependencies(string assetBundleName)
// 获取指定assetBundleName的所有依赖
public string[] GetAllDependencies(string assetBundleName)

说明：入参 assetBundleName 不区分大小写，建议使用小写，如果使用大写会自动转换为小写。

3）AssetDatabase 获取所有资源名、删除资源

// 获取所有AssetBundle资源名
public static string[] GetAllAssetBundleNames()
// 根据assetBundleName删除AssetBundle
public static bool RemoveAssetBundleName(string assetBundleName, bool forceRemove)
// 刷新Project视图目录, 相当于右键手动刷新
public static void Refresh()

4）AssetImporter 设置资源名

// 获取AssetImporter, 资源文件路径
public static AssetImporter GetAtPath(string path)
// 获取/设置资源文件名
public string assetBundleName { get; set; }

5）BuildPipeline 压缩资源

// 压缩所有标记为AssetBundle的资源
public static AssetBundleManifest BuildAssetBundles(string outputPath, // 压缩文件输出路径BuildAssetBundleOptions assetBundleOptions, // 压缩算法BuildTarget targetPlatform // 平台
)
// BuildAssetBundleOptions.None: LZMA压缩算法, 压缩比大, 加载慢, 使用前需要整体解压
// BuildAssetBundleOptions.ChunkBasedCompression: LZ4压缩算法, 压缩比中等, 加载快可以加载指定资源而不用解压全部
// BuildAssetBundleOptions.UncompressedAssetBundle: 不压缩, 加载快

6）WWW 获取网络资源

// 获取WWW
public static WWW LoadFromCacheOrDownload(string url, int version)
// 获取AssetBundle
public AssetBundle assetBundle { get; }

说明：WWW 被 Unity3D 官方标记为过时了，建议使用 UnityWebRequest。

7）UnityWebRequest 获取网络资源

UnityWebRequest webRequest = UnityWebRequestAssetBundle.GetAssetBundle(uri)
yield return webRequest.SendWebRequest()
AssetBundle assetBundle = DownloadHandlerAssetBundle.GetContent(webRequest)

2 资源命名

Asset 资源主要有脚本、图片、网格、模型、预设体等，在 Assets 窗口选中资源，在 Inspector 窗口选择 AssetBundle 下拉列表，选择 New 给资源添加 AssetBundle 名，如下：

说明：AssetBundle 名不区分大小写，如果输入大写会自动转换为小写。只有添加了 AssetBundle 名的资源才能通过 BuildPipeline.BuildAssetBundles() 打包压缩。

3 资源压缩

1）创建目录及原资源

在 Assets 目录下创建 AssetBundles 目录（存放资源）和 Editor 目录（存放资源压缩脚本），在 AssetBundles 目录下创建 Compress 目录（存放压缩文件）和 Raw 目录（存放原资源文件），再在 Raw 目录下创建 Textures 目录（存放了一张图片 Picture）、Materials 目录（存放了一个材质 Material，并且依赖 Picture）、Prefabs 目录（存放了一个预设体 Quad，并且依赖 Material），目录结构如下：

2）自动压缩脚本

AssetCompressor.cs

using System.IO;
using UnityEditor;
using UnityEngine;public class AssetCompressor : Editor {// G:/Unity3d/AssetBundleDemo/Assets/AssetBundles/Rawprivate static string rawPath = Application.dataPath + "/AssetBundles/Raw";// G:/Unity3d/AssetBundleDemo/Assets/AssetBundles/Compressprivate static string compressPath = Application.dataPath + "/AssetBundles/Compress";[MenuItem("AssetBundle/CompressAssets")]public static void CompressAssets() { // 打包rawPath目录的资源, 生成压缩资源到compressPath目录ClearAllFilesBundleName();SetAssetBundlesName(rawPath);BuildAssetBundles();ClearAllFilesBundleName();AssetDatabase.Refresh(); // 刷新Project视图目录, 相当于右键手动刷新}private static void BuildAssetBundles() { // 压缩资源BuildPipeline.BuildAssetBundles(compressPath, // 压缩包输出包路径BuildAssetBundleOptions.ChunkBasedCompression, // 压缩算法BuildTarget.StandaloneWindows64 // Windows平台);}private static void ClearAllFilesBundleName() { // 删除所有AssetBundle名string[] names = AssetDatabase.GetAllAssetBundleNames();foreach (string name in names) {AssetDatabase.RemoveAssetBundleName(name, true);}}private static void SetAssetBundlesName(string rootPath) { // 设置资源的Bundle名DirectoryInfo rootInfo = new DirectoryInfo(rootPath);FileSystemInfo[] fileInfos = rootInfo.GetFileSystemInfos();foreach (FileSystemInfo fileInfo in fileInfos) {if (fileInfo is DirectoryInfo) {SetAssetBundlesName(fileInfo.FullName); // 递归遍历子文件夹下所有文件} else if (!fileInfo.Name.EndsWith(".meta")) {SetAssetBundleName(fileInfo.FullName);}}}private static void SetAssetBundleName(string filePath) { // 设置资源的Bundle名// 导入的相对路径(G:/Unity3d/AssetBundleDemo/Assets/AssetBundles/Compress/prefabs/quad.prefab)string impoterPath = "Assets/" + filePath.Substring(Application.dataPath.Length + 1);AssetImporter assetImporter = AssetImporter.GetAtPath(impoterPath);if (assetImporter != null) {filePath = filePath.Substring(rawPath.Length + 1); // 去源文件前缀(可选, 建议使用)// filePath = filePath.Substring(filePath.LastIndexOf("\\") + 1); // 去所有前缀(可选, 不建议使用)// 去后缀(可选, 不去后缀刷新目录后会报错, 但不影响资源压缩和后续资源加载)// filePath = filePath.Remove(filePath.LastIndexOf("."));assetImporter.assetBundleName = filePath;}}
}

说明：AssetCompressor.cs 文件需要放在 Editor 目录下，编译成功后，在菜单栏可以看到 AssetBundle 菜单，如下：

点击 CompressAssets 选项，会将 Assets/AssetBundles/Raw 目录下的资源打包压缩至 Assets/AssetBundles/Compress 目录，如下：

注意：运行上述代码后，会报以下错误，这是因为文件已经压缩了，但还是以 “.prefab”、“.jpg”、“.mat” 为后缀，被 Unity3D 识别为损坏文件。该错误不影响压缩文件生成，也不影响后续资源加载，可以忽略。如果不想出现以下报错，可以将去后缀的注释代码打开。

3）压缩文件

打开 Compress.manifest 文件如下：

ManifestFileVersion: 0
CRC: 3680739267
AssetBundleManifest:AssetBundleInfos:Info_0:Name: materials/material.matDependencies:Dependency_0: textures/picture.jpgInfo_1:Name: prefabs/quad.prefabDependencies:Dependency_0: materials/material.matInfo_2:Name: textures/picture.jpgDependencies: {}

说明：后续要加载资源时，如果不清楚 AssetBundle 名，可以在 Compress.manifest 文件中查看相应 Name 值。可以看到，这里的 Name 值也全都自动转换为小写了，在加载资源时，如果传入大写的也能正常获取到相应资源。

4 加载本地资源

1）加载简单资源

// targetPath="ptextures/picture.jpg"
public static T LoadAsset<T>(string targetPath) { // 加载资源// G:/Unity3d/AssetBundleDemo/Assets/AssetBundles/Compress/ptextures/picture.jpgAssetBundle targetBundle = AssetBundle.LoadFromFile(compressPath + "/" + targetPath);string fileName = targetPath.Substring(targetPath.LastIndexOf("/") + 1); // picture.jpgobject obj = targetBundle.LoadAsset(fileName);if (obj != null) {return (T) obj;}return default(T);
}

说明：如果没有依赖资源，可以使用该方法；如果有依赖资源，就会出现异常。当 targetPath = "prefabs/quad.prefab" 时，创建的 Quad 显示如下，Quad 显示品红，表示它依赖的材质和图片缺失。

2）加载有依赖的资源

LocalAssetLoader.cs

using UnityEngine;public class LocalAssetLoader {// G:/Unity3d/AssetBundleDemo/Assets/AssetBundles/Compressprivate static string compressPath = Application.dataPath + "/AssetBundles/Compress"; // 压缩文件根路径// G:/Unity3d/AssetBundleDemo/Assets/AssetBundles/Compress/Compressprivate static string rootManifestPath = compressPath + "/Compress"; // 根manifest文件路径(Compress.manifest文件绝对路径)public static T LoadAsset<T>(string targetPath) { // 加载资源LoadDependencies(targetPath);return LoadTarget<T>(targetPath);}private static void LoadDependencies(string targetPath) { // 加载目标资源的依赖AssetBundle manifestBundle = AssetBundle.LoadFromFile(rootManifestPath);// 解压Manifest文件, 传入的参数不区分大小写(如果是大写, 会自动转换为小写)AssetBundleManifest manifest = manifestBundle.LoadAsset<AssetBundleManifest>("AssetBundleManifest");string[] dependencies = manifest.GetAllDependencies(targetPath); // 获取目标文件的所有依赖for (int i = 0; i < dependencies.Length; i++) {string filePath = compressPath + "/" + dependencies[i];AssetBundle.LoadFromFile(filePath);}}private static T LoadTarget<T>(string targetPath) { // 加载目标资源AssetBundle targetBundle = AssetBundle.LoadFromFile(compressPath + "/" + targetPath);string fileName = targetPath.Substring(targetPath.LastIndexOf("/") + 1);object obj = targetBundle.LoadAsset(fileName);if (obj != null) {return (T) obj;}return default(T);}
}

说明：manifest.GetAllDependencies()、AssetBundle.LoadFromFile()、targetBundle.LoadAsset() 的入参不区分大小写，因此传入的 targetPath 也可以不区分大小写。

3）调用 LocalAssetLoader 加载资源

SimpleLoad.cs

using UnityEngine;public class SimpleLoad : MonoBehaviour {private void Start() {GameObject obj = LocalAssetLoader.LoadAsset<GameObject>("prefabs/quad.prefab"); // 加载预设体// GameObject obj = LocalAssetLoader.LoadAsset<GameObject>("Prefabs/Quad.prefab"); // 加载预设体Instantiate(obj);}
}

说明：由于 LocalAssetLoader.LoadAsset 的入参不区分大小写，因此传入 "prefabs/quad.prefab" 和 "Prefabs/Quad.prefab" 都能正确加载资源。

运行效果如下：

5 使用 WWW 加载服务器资源

W3AssetLoader.cs

using System;
using System.Collections;
using UnityEngine;public class W3AssetLoader : MonoBehaviour {private string compressPath; // 压缩文件根路径private string rootManifestPath; // 根manifest文件路径private static W3AssetLoader instance; // 单例private void Awake() {instance = this;// compressPath = GetW3Path(Application.dataPath + "/AssetBundle/Compress");compressPath = "https://gitcode.net/m0_37602827/AssetBundleDemo/-/raw/master/Assets/AssetBundle/Compress";rootManifestPath = compressPath + "/Compress";}public static void LoadAsset<T>(string targetPath, Action<T> action) { // 加载资源instance.StartCoroutine(instance.LoadAssetCorutine<T>(targetPath, action));}private IEnumerator LoadAssetCorutine<T>(string targetPath, Action<T> action) { // 加载资源的协程yield return LoadDependencies(targetPath);yield return LoadTarget(targetPath, action);}private IEnumerator LoadDependencies(string targetPath) { // 加载目标资源的依赖WWW w3 = WWW.LoadFromCacheOrDownload(rootManifestPath, 1);yield return w3;AssetBundle assetBundle = w3.assetBundle;if (assetBundle != null) {AssetBundleManifest manifest = assetBundle.LoadAsset<AssetBundleManifest>("AssetBundleManifest");if (manifest != null) {string[] dependencies = manifest.GetAllDependencies(targetPath); // 获取目标文件的所有依赖for (int i = 0; i < dependencies.Length; i++) {string filePath = compressPath + "/" + dependencies[i];w3 = WWW.LoadFromCacheOrDownload(filePath, 1);yield return w3;assetBundle = w3.assetBundle;}}}}private IEnumerator LoadTarget<T>(string targetPath, Action<T> action) { // 加载目标文件string fullPath = compressPath + "/" + targetPath;WWW w3 = WWW.LoadFromCacheOrDownload(fullPath, 1);yield return w3;AssetBundle assetBundle = w3.assetBundle;if (assetBundle != null) {string fileName = targetPath.Substring(targetPath.LastIndexOf("/") + 1);object obj = assetBundle.LoadAsset(fileName); // 解压文件if (obj != null && action != null) {action.Invoke((T) obj);}}}private string GetW3Path(string path) {#if UNITY_EDITOR_WIN || UNITY_STANDALONE_WINpath = "file:///" + path;#elif UNITY_EDITOR_OSX || UNITY_STANDALONE_OSXpath = "file://" + path;#endifreturn path;}
}

SimpleLoad.cs

using UnityEngine;public class SimpleLoad : MonoBehaviour {private void Start() {W3AssetLoader.LoadAsset<GameObject>("prefabs/quad", Callback);// W3AssetLoader.LoadAsset<GameObject>("Prefabs/Quad", Callback);}private void Callback(GameObject obj) {Instantiate(obj);}
}

注意：W3AssetLoader.LoadAsset() 方法的入参不要加 ".prefab" 后缀，并且入参也不区分大小写。

6 使用 UnityWebRequest 加载服务器资源

WebAssetLoader.cs

using System;
using System.Collections;
using UnityEngine;
using UnityEngine.Networking;public class WebAssetLoader : MonoBehaviour {private string compressPath; // 压缩文件根路径private string rootManifestPath; // 根manifest文件路径private static WebAssetLoader instance; // 单例private void Awake() {instance = this;// compressPath = GetW3Path(Application.dataPath + "/AssetBundle/Compress");compressPath = "https://gitcode.net/m0_37602827/AssetBundleDemo/-/raw/master/Assets/AssetBundle/Compress";rootManifestPath = compressPath + "/Compress";}public static void LoadAsset<T>(string targetPath, Action<T> action) { // 加载资源instance.StartCoroutine(instance.LoadAssetCorutine<T>(targetPath, action));}private IEnumerator LoadAssetCorutine<T>(string targetPath, Action<T> action) { // 加载资源的协程yield return LoadDependencies(targetPath);yield return LoadTarget(targetPath, action);}private IEnumerator LoadDependencies(string targetPath) { // 加载目标资源的依赖UnityWebRequest webRequest = UnityWebRequestAssetBundle.GetAssetBundle(rootManifestPath);yield return webRequest.SendWebRequest();AssetBundle assetBundle = DownloadHandlerAssetBundle.GetContent(webRequest);if (assetBundle != null) {AssetBundleManifest manifest = assetBundle.LoadAsset<AssetBundleManifest>("AssetBundleManifest");if (manifest != null) {string[] dependencies = manifest.GetAllDependencies(targetPath); // 获取目标文件的所有依赖for (int i = 0; i < dependencies.Length; i++) {string filePath = compressPath + "/" + dependencies[i];webRequest = UnityWebRequestAssetBundle.GetAssetBundle(filePath);yield return webRequest.SendWebRequest();assetBundle = DownloadHandlerAssetBundle.GetContent(webRequest);}}}}private IEnumerator LoadTarget<T>(string targetPath, Action<T> action) { // 加载目标文件string fullPath = compressPath + "/" + targetPath;UnityWebRequest webRequest = UnityWebRequestAssetBundle.GetAssetBundle(fullPath);yield return webRequest.SendWebRequest();AssetBundle assetBundle = DownloadHandlerAssetBundle.GetContent(webRequest);if (assetBundle != null) {string fileName = targetPath.Substring(targetPath.LastIndexOf("/") + 1);object obj = assetBundle.LoadAsset(fileName); // 解压文件if (obj != null && action != null) {action.Invoke((T) obj);}}}private string GetW3Path(string path) {#if UNITY_EDITOR_WIN || UNITY_STANDALONE_WINpath = "file:///" + path; // Windows平台#elif UNITY_EDITOR_OSX || UNITY_STANDALONE_OSXpath = "file://" + path; // Mac平台#endifreturn path;}
}

SimpleLoad.cs

using UnityEngine;public class SimpleLoad : MonoBehaviour {private void Start() {WebAssetLoader.LoadAsset<GameObject>("prefabs/quad.prefab", Callback);}private void Callback(GameObject obj) {Instantiate(obj);}
}

注意：WebAssetLoader.LoadAsset() 的入参需要添加 ".prefab" 后缀，并且入参区分大小写。