前言

先捋一下打AB包的整体思路，首先，Unity4.6版本之后就使用了全新的打包接口

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

无论是全新打包还是增量打包都是使用这个API，所以一切的一切，都要围绕这个API开始讲起。

该API有四个参数

string outputPath

AssetBundleBuild[] builds

BuildAssetBundleOptions assetBundleOptions

BuildTarget targetPlatform

参数1：outputPath比较好理解，打包输出路径，打包时目标文件夹必须存在

参数2：builds的意思是，你要告诉API，哪些资源需要打成ab包，该参数是打AB包的核心所在，资源规划、打包策略都是在生成该参数的时候完成的，再次提示，参数2是由无数个AssetBundleBuild组成

参数3：该参数的作用是告诉API一些规则，下面列出了参数3的源代码

public enum BuildAssetBundleOptions
    {
        None = 0,
        UncompressedAssetBundle = 1,
        CollectDependencies = 2,
        CompleteAssets = 4,
        DisableWriteTypeTree = 8,
        DeterministicAssetBundle = 16,
        ForceRebuildAssetBundle = 32,
        IgnoreTypeTreeChanges = 64,
        AppendHashToAssetBundleName = 128,
        ChunkBasedCompression = 256,
        StrictMode = 512,
        DryRunBuild = 1024,
        DisableLoadAssetByFileName = 4096,
        DisableLoadAssetByFileNameWithExtension = 8192,
        EnableProtection = 16384
    }

参数3的使用方式也比较简单，根据需要选择

private BuildAssetBundleOptions MakeBuildOptions()
{
    // For the new build system, unity always need BuildAssetBundleOptions.CollectDependencies and BuildAssetBundleOptions.DeterministicAssetBundle
    // 除非设置ForceRebuildAssetBundle标记，否则会进行增量打包
    BuildAssetBundleOptions opt = BuildAssetBundleOptions.None;
    opt |= BuildAssetBundleOptions.StrictMode; //Do not allow the build to succeed if any errors are reporting during it.
    opt |= BuildAssetBundleOptions.DeterministicAssetBundle;

    if (CompressOption == ECompressOption.Uncompressed)
        opt |= BuildAssetBundleOptions.UncompressedAssetBundle;
    else if (CompressOption == ECompressOption.ChunkBasedCompressionLZ4)
        opt |= BuildAssetBundleOptions.ChunkBasedCompression;

    if (IsForceRebuild)
        opt |= BuildAssetBundleOptions.ForceRebuildAssetBundle; //Force rebuild the asset bundles
    if (IsAppendHash)
        opt |= BuildAssetBundleOptions.AppendHashToAssetBundleName; //Append the hash to the assetBundle name
    if (IsDisableWriteTypeTree)
        opt |= BuildAssetBundleOptions.DisableWriteTypeTree; //Do not include type information within the asset bundle (don't write type tree).
    if (IsIgnoreTypeTreeChanges)
        opt |= BuildAssetBundleOptions.IgnoreTypeTreeChanges; //Ignore the type tree changes when doing the incremental build check.
    if (UseFullPath)
        opt |= (BuildAssetBundleOptions.DisableLoadAssetByFileName | BuildAssetBundleOptions.DisableLoadAssetByFileNameWithExtension);

    return opt;
}

看不懂 |=符号的小伙伴需要补一下C#的知识。

参数4：目标平台，这个很简单，需要打包哪个平台就传入哪个枚举即可。