Unity AssetBundle 设置名称优化

原因

在大部分的 Unity 分析打包 AssetBundle 过程中，是采用对资源设置 AssetBundle 名称标签的方式来进行打包，类似如下：

public static void SetBundleName(string assetPath, string bundleName)
{
var importer = AssetImporter.GetAtPath(assetPath);
if (importer && importer.assetBundleName != bundleName)
{
importer.assetBundleName = bundleName;
}
}

private static void BuildAssetBundlesInter(string outputPath, AssetBundleBuildOptions options)
{
AssetBundleManifest manifest = BuildPipeline.BuildAssetBundles(outputPath,
BuildAssetBundleOptions.UncompressedAssetBundle, GetBuildTarget());
}

每设置一个资源的 AssetBundle 名称，都会导致 Unity 写入其 .meta 文件，这样在分析的过程耗费不少时间。而且在打包完毕，又得重新设置所有资源的 AssetBundle 名称为空，否则仓库会提示有文件变化。

思路

修改流程，改成传入 AssetBundleBuild[] 的方式进行打包，这样就无需设置资源的 AssetBundle 名称。但是不能简单的把结果保存为 AssetBundleBuild[] 数组对象，因为打包工具支持当次不再分析资源，直接使用上一次的分析结果。所以要把 AssetBundleBuild[] 结果存为临时文件，方便下次使用，正常来说，这个临时文件一般只对当天的资源有效即可，当更新了资源，肯定得重新分析资源，不能再使用上次的结果。所以，只需要把这临时文件放在 Temp 目录下即可。

解决

创建一个独立类，来管理分析的 AssetBundle 构建信息：

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.Serialization.Formatters.Binary;
using UnityEditor;

/// <summary>
/// AssetBundle 分析映射
/// </summary>
public static class AssetBundleBuildMap
{
private static AssetBundleMap assetBundleMap;

public static void Clear()
{
if (assetBundleMap != null)
{
assetBundleMap = null;
}
}

/// <summary>
/// 普通资源设置 AssetBundle 名称接口
/// </summary>
/// <param name="assetPath"></param>
/// <param name="assetBundleName"></param>
public static void SetAssetPathAssetBundleName(string assetPath, string assetBundleName)
{
if (assetBundleMap == null)
{
assetBundleMap = new AssetBundleMap();
}
assetBundleMap.AddMap(assetPath, assetBundleName);
}

public static bool IsAssetPathHasAssetBundleName(string assetPath)
{
if (assetBundleMap == null)
{
return false;
}
return assetBundleMap.assetPathSet.Contains(assetPath);
}

public static List<string> GetAllAssetBundleNames()
{
if (assetBundleMap == null)
{
return null;
}
List<string> allAssetBundleNames = assetBundleMap.assetBundleDict.Keys.ToList();
allAssetBundleNames.Sort(EditorUtility.NaturalCompare);
return allAssetBundleNames;
}

public static List<string> GetAssetPathsFromAssetBundle(string assetBundleName)
{
if (assetBundleMap == null)
{
return null;
}
List<string> assetPaths;
if (assetBundleMap.assetBundleDict.TryGetValue(assetBundleName, out assetPaths))
{
assetPaths.Sort(EditorUtility.NaturalCompare);
return assetPaths;
}
return null;
}

/// <summary>
/// 最终需要进行打包的资产构建列表
/// </summary>
/// <returns></returns>
public static AssetBundleBuild[] GetAssetBundleBuilds()
{
List<AssetBundleBuild> assetBundleBuilds = new List<AssetBundleBuild>();
string tempPath = "Temp/AssetBundleBuildAnalyze";
if (assetBundleMap == null)
{
assetBundleMap = AssetBundleMap.MakeByLoad(tempPath);
}
else
{
assetBundleMap.Save(tempPath);
}
assetBundleBuilds.AddRange(assetBundleMap.GetBuilds());

return assetBundleBuilds.ToArray();
}

private class AssetBundleMap
{
public readonly HashSet<string> assetPathSet = new HashSet<string>();
public Dictionary<string, List<string>> assetBundleDict = new Dictionary<string, List<string>>();

public void AddMap(string assetPath, string assetBundleName)
{
if (string.IsNullOrEmpty(assetPath) || string.IsNullOrEmpty(assetBundleName))
{
return;
}
if (assetPathSet.Contains(assetPath))
{
return;
}

assetPathSet.Add(assetPath);
List<string> assetPaths;
if (assetBundleDict.TryGetValue(assetBundleName, out assetPaths))
{
assetPaths.Add(assetPath);
}
else
{
assetPaths = new List<string> { assetPath };
assetBundleDict.Add(assetBundleName, assetPaths);
}
}

public List<AssetBundleBuild> GetBuilds()
{
List<AssetBundleBuild> assetBundleBuilds = new List<AssetBundleBuild>();
foreach (var kv in assetBundleDict)
{
assetBundleBuilds.Add(new AssetBundleBuild() { assetBundleName = kv.Key, assetNames = kv.Value.ToArray() });
}
return assetBundleBuilds;
}

public void Save(string tempPath)
{
using (MemoryStream stream = new MemoryStream())
{
new BinaryFormatter().Serialize(stream, assetBundleDict);
File.WriteAllBytes(tempPath, stream.ToArray());
}
}

public static AssetBundleMap MakeByLoad(string tempPath)
{
AssetBundleMap map = new AssetBundleMap();
if (File.Exists(tempPath))
{
byte[] bytes = File.ReadAllBytes(tempPath);
using (MemoryStream stream = new MemoryStream(bytes))
{
map.assetBundleDict = new BinaryFormatter().Deserialize(stream) as Dictionary<string, List<string>>;
}
}
return map;
}
}
}

最终调用的方式如下：

private static void BuildAssetBundlesInter(string outputPath, AssetBundleBuildOptions options)
{
AssetBundleBuild[] assetBundleBuilds = AssetBundleBuildMap.GetAssetBundleBuilds();

AssetBundleManifest manifest = BuildPipeline.BuildAssetBundles(outputPath, assetBundleBuilds,
BuildAssetBundleOptions.UncompressedAssetBundle, GetBuildTarget());
AssetBundleBuildMap.Clear();
}