# AssetBundle 创建与加载

AssetBundle 只能用代码创建和加载
在创建前需要先为资源分配资源包，如图：

# AssetBundle 的创建

区分平台（Windows、OSX、Linux 等）
区分创建方式（是否压缩、压缩方式等）

	using System.IO;
	using UnityEditor;

	namespace Common
	{
	/// <summary>
	/// CreateAssetBundles
	/// </summary>
	public class CreateAssetBundles
	{
	//[MenuItem("Assets/Build AssetBundles")]
	[MenuItem("Build/Build AssetBundles")]
	private static void BuildAllAssetBundles()
	{
	string assetBundleDirectory = "Assets/StreamingAssets/AssetBundles";
	BuildAssetBundleOptions assetBundleOptions;
	BuildTarget targetPlatform;

	#if UNITY_EDITOR
	assetBundleOptions = BuildAssetBundleOptions.UncompressedAssetBundle;
	targetPlatform = BuildTarget.StandaloneWindows64;
	#elif UNITY_STANDALONE_WIN //Windows 独立平台应用程序
	assetBundleOptions = BuildAssetBundleOptions.UncompressedAssetBundle;
	targetPlatform = BuildTarget.StandaloneWindows64;
	#elif UNITY_STANDALONE_OSX //Mac OS X（包括 Universal、PPC 和 Intel 架构）
	assetBundleOptions = BuildAssetBundleOptions.UncompressedAssetBundle;
	targetPlatform = BuildTarget.StandaloneOSX;
	#elif UNITY_STANDALONE_LINUX //Linux
	assetBundleOptions = BuildAssetBundleOptions.UncompressedAssetBundle;
	targetPlatform = BuildTarget.StandaloneLinux;
	#elif UNITY_ANDROID
	assetBundleOptions = BuildAssetBundleOptions.ChunkBasedCompression;
	targetPlatform = BuildTarget.Android;
	#elif UNITY_IOS
	assetBundleOptions = BuildAssetBundleOptions.ChunkBasedCompression;
	targetPlatform = BuildTarget.iOS;
	#elif UNITY_WEBGL
	assetBundleOptions = BuildAssetBundleOptions.ChunkBasedCompression;
	targetPlatform = BuildTarget.WebGL;
	#endif

	if (!Directory.Exists(assetBundleDirectory))
	{
	Directory.CreateDirectory(assetBundleDirectory);
	}
	else
	{
	Directory.Delete(assetBundleDirectory, true);
	Directory.CreateDirectory(assetBundleDirectory);
	}
	BuildPipeline.BuildAssetBundles(assetBundleDirectory, assetBundleOptions, targetPlatform);
	}
	}
	}

# AssetBundle 的加载

两种加载方式：通过网络请求加载（UnityWebRequest）、通过本地存储加载（AssetBundle.LoadFromFile ()）
本工具类中使用网络请求加载方式，目的是为了适配更多的设备
同一个 ab 包中如果有多个同名文件，则只会加载第一个匹配的文件
加载目标 ab 包前，需要先加载它的依赖 ab 包（如果存在）
加载目标 ab 包后，调用委托处理其他逻辑
加载的 ab 包在使用完后需要要卸载，防止占用内存

	using System;
	using System.Collections;
	using UnityEngine;
	using UnityEngine.Networking;

	namespace Common
	{
	/// <summary>
	///ab 包管理器
	/// </summary>
	public class AssetBundleManager
	{
	/// <summary>
	/// 加载资源包
	/// </summary>
	/// <param name="path"> 路径 & lt;/param>
	/// <param name="action"> 委托 & lt;/param>
	/// <returns></returns>
	public static IEnumerator LoadAssetBundle(string path, Action<AssetBundle> action)
	{
	string assetBundleName = path.Split('/')[^1];
	string startPath = path.Substring(0, path.LastIndexOf('/'));

	// 获取 AssetBundles 文件
	UnityWebRequest request_0 = UnityWebRequestAssetBundle.GetAssetBundle(startPath + "/AssetBundles", 0);
	yield return request_0.SendWebRequest();

	if (request_0.result != UnityWebRequest.Result.Success)
	{
	Debug.LogError("Failed to load AssetBundle：" + request_0.error);
	}
	else
	{
	AssetBundle bundle_0 = DownloadHandlerAssetBundle.GetContent(request_0);

	// 获取 manifest 文件
	AssetBundleManifest manifest_0 = bundle_0.LoadAsset("AssetBundleManifest") as AssetBundleManifest;
	bundle_0.Unload(false);

	// 查找并加载依赖文件
	string[] dependencies = manifest_0.GetAllDependencies(assetBundleName);
	AssetBundle[] bundles = new AssetBundle[dependencies.Length];

	for (int i = 0; i < dependencies.Length; i++)
	{
	string dependenciesPath = startPath + '/' + dependencies[i];
	UnityWebRequest requests = UnityWebRequestAssetBundle.GetAssetBundle(dependenciesPath, 0);
	yield return requests.SendWebRequest();

	if (requests.result != UnityWebRequest.Result.Success)
	{
	Debug.LogError("Failed to load AssetBundle：" + requests.error);
	}
	else
	{
	bundles[i] = DownloadHandlerAssetBundle.GetContent(requests);
	}
	}

	// 取出资源
	UnityWebRequest request = UnityWebRequestAssetBundle.GetAssetBundle(path, 0);
	yield return request.SendWebRequest();

	if (request.result != UnityWebRequest.Result.Success)
	{
	Debug.LogError("Failed to load AssetBundle：" + request.error);
	}
	else
	{
	AssetBundle bundle = DownloadHandlerAssetBundle.GetContent(request);
	action(bundle);
	bundle.Unload(false);
	}

	foreach (AssetBundle item in bundles)
	{
	item.Unload(false);
	}
	}
	}
	}
	}

# 使用方法

创建
点击按钮创建 ab 包，如图：

加载

	private void OnGUI()
	{
	if (GUILayout.Button("LoadAssetBundle"))
	{
	this.StartCoroutine(AssetBundleManager.LoadAssetBundle(Application.streamingAssetsPath + "/AssetBundles/model.model", TestAction));
	}
	}

	private void TestAction(AssetBundle bundle)
	{
	GameObject receive = bundle.LoadAsset<GameObject>("Cube_1");
	Instantiate(receive, Vector3.zero, Quaternion.identity);
	}