一、前景回顾
上文写到PC、IOS、Android项目加载ab包资源，地址：
http://t.csdnimg.cn/RdB3i
二、WebGL打包AB包
打包的步骤和上文中的操作相同，唯一的不同就是在Build页面里Build Target选择WebGL。
三、WebGL加载AB包
（1）内置渲染管线
当项目使用内置渲染管线时，所有材质的Shader为Standard。
（2）通用渲染管线URP
1、当项目为URP时，首先需要在Package Manager里导入Universal RP，如图
2、Create—Rendering—URP Assets(with Universal Render)来创建URP配置文件，如图
3、在Edit—Project Settings—Graphics，修改为刚才创建的文件。这一步操作完成后，场景中的物体材质可能会变成了洋红色。此时项目已由内置着色器转换为URP着色器。
4、Edit—Render Pipeline—Universal Render Pipeline—Upgrade Project Materials to UniversalRP Materials更新材质。 也可以手动修改材质的Shader为Universal Render Pipeline/Lit。如图
5、在软件中运行项目，加载出来的材质是洋红色的（不用担心）。
6、导出项目在本地浏览器加载，加载出来的模型材质是正常的。
四、加载ab包脚本
WebGL使用UnityWebRequest加载依赖和ab包
//主包 private AssetBundle abMain = null; //依赖 private AssetBundleManifest abMainfest = null; //缓存字典，防止多次加载 private Dictionary<string, AssetBundle> abDic = new Dictionary<string, AssetBundle>(); /// <summary> /// 平台对应的路径 /// </summary> private string PathURL = Application.streamingAssetsPath + "/"; /// <summary> /// 平台对应的主包名称 /// </summary> private string MainABName = "WebGL"; //UnityWebRequest加载依赖 private IEnumerator LoadDependences(string abName) { //加载主包 if (abMain == null) { UnityWebRequest abRequest = UnityWebRequestAssetBundle.GetAssetBundle(PathURL + MainABName); yield return abRequest.SendWebRequest(); abMain = DownloadHandlerAssetBundle.GetContent(abRequest); //获取主包下的AssetBundleManifest资源文件（存有依赖信息） abMainfest = abMain.LoadAsset<AssetBundleManifest>("AssetBundleManifest"); } //加载依赖 AssetBundle ab = null; string[] dependences = abMainfest.GetAllDependencies(abName); if (dependences.Length > 0) { for (int i = 0; i < dependences.Length; i++) { if (!abDic.ContainsKey(dependences[i])) { UnityWebRequest DepRequest = UnityWebRequestAssetBundle.GetAssetBundle(PathURL + dependences[i]); yield return DepRequest.SendWebRequest(); ab = DownloadHandlerAssetBundle.GetContent(DepRequest); abDic.Add(dependences[i], ab); } } } } //UnityWebRequest加载 public void LoadByRequest<T>(string abName, string resName, UnityAction<T> callBack) where T : Object { StartCoroutine(ReallyLoadByRequest<T>(abName, resName, callBack)); } private IEnumerator ReallyLoadByRequest<T>(string abName, string resName, UnityAction<T> callBack) where T : Object { yield return StartCoroutine(LoadDependences(abName)); if (!abDic.ContainsKey(abName)) { UnityWebRequest abRequest3 = UnityWebRequestAssetBundle.GetAssetBundle(PathURL + abName); yield return abRequest3.SendWebRequest(); AssetBundle ab = DownloadHandlerAssetBundle.GetContent(abRequest3); abDic[abName] = ab; } T loadedResource = abDic[abName].LoadAsset<T>(resName); callBack(loadedResource as T); } //单个包卸载 public void UnLoad(string abName) { if (abDic.ContainsKey(abName)) { abDic[abName].Unload(false); //注意缓存需一并移除 abDic.Remove(abName); } } //所有包卸载 public void UnLoadAll() { AssetBundle.UnloadAllAssetBundles(true); //注意清空缓存 abDic.Clear(); abMain = null; abMainfest = null; }测试
public Transform[] bigRackPos; public Transform[] smallRackPos; public void TestOne() { LoadByRequest<GameObject>("bigrack", "BigRack", (obj) => { for (int i = 0; i < bigRackPos.Length; i++) { //实例化预设 Instantiate(obj, bigRackPos[i].position, Quaternion.identity); } }); } public void TestTwo() { LoadByRequest<GameObject>("smallrack", "SmallRack", (obj) => { for (int i = 0; i < smallRackPos.Length; i++) { //实例化预设 Instantiate(obj, smallRackPos[i].position, Quaternion.Euler(0, 90, 0)); } }); }五、报错
在WebGL项目中加载ab包，不能同时加载加载多个ab包。
测试代码中，我写了两个方法来加载两个ab包，如果我把这两个方法写在Start方法里同时运行，就会报错并且第二个方法加载不出来。
private void Start() { TestOne(); TestTwo(); }错误显示
The AssetBundle 'G:/Unity Project/cgf/MyScene/NormalAssetBundle/Assets/StreamingAssets/WebGL' can't be loaded because another AssetBundle with the same files is already loaded.
六、解答
根据PC端加载ab包的思路来实现web端的加载，当同时加载多个ab包时，就会同时调用多次这个协程，就会出现冲突的情况，也就是上述这个问题。这里是显示的加载主包WebGL冲突的问题，大家可能也会遇到加载依赖包冲突的问题，针对目前出现的问题作出修改。
1、当我们对资源进行打包时，不再把相同的资源包打成其他包的依赖包，而是让每个包都独立，这样加载起来就舍弃了加载依赖的过程，也就避免了加载依赖包冲突的问题。打包如图
2、没了加载依赖包的操作也就不用加载主包了（加载主包是为了获取各个包之间的依赖关系，现在每个包都是独立的，不存在依赖了），这就删除掉之前的加载依赖和主包的协程方法LoadDependences即可。另外在加载协程了去掉 这句就可以了。
yield return StartCoroutine(LoadDependences(abName));
3、完整代码
//缓存字典，防止多次加载 private Dictionary<string, AssetBundle> abDic = new Dictionary<string, AssetBundle>(); /// <summary> /// 平台对应的路径 /// </summary> private string PathURL = Application.streamingAssetsPath + "/"; //UnityWebRequest加载 public void LoadByRequest<T>(string abName, string resName, UnityAction<T> callBack) where T : Object { StartCoroutine(ReallyLoadByRequest<T>(abName, resName, callBack)); } private IEnumerator ReallyLoadByRequest<T>(string abName, string resName, UnityAction<T> callBack) where T : Object { if (!abDic.ContainsKey(abName)) { UnityWebRequest abRequest3 = UnityWebRequestAssetBundle.GetAssetBundle(PathURL + abName); yield return abRequest3.SendWebRequest(); AssetBundle ab = DownloadHandlerAssetBundle.GetContent(abRequest3); abDic[abName] = ab; } T loadedResource = abDic[abName].LoadAsset<T>(resName); callBack(loadedResource as T); } //单个包卸载 public void UnLoad(string abName) { if (abDic.ContainsKey(abName)) { abDic[abName].Unload(false); //注意缓存需一并移除 abDic.Remove(abName); } } //所有包卸载 public void UnLoadAll() { AssetBundle.UnloadAllAssetBundles(true); //注意清空缓存 abDic.Clear(); }4、测试
private void Start() { TestOne(); TestTwo(); } public void TestOne() { LoadByRequest("bigrack", "BigRack", (obj) => { for (int i = 0; i < bigRackPos.Length; i++) { //实例化预设 Instantiate(obj, bigRackPos[i].position, bigRackPos[i].rotation); } }); } public void TestTwo() { LoadByRequest("smallrack", "SmallRack", (obj) => { for (int i = 0; i < smallRackPos.Length; i++) { //实例化预设 Instantiate(obj, smallRackPos[i].position, smallRackPos[i].rotation); } }); }