https://www.xuanyusong.com/archives/4607
AssetBundle.LoadFromMemory基本上是无法在手机上用的，因为要多占一份内存，所以大多Unity项目都不进行资源加密。
Unity2017.2提供了一个新的API AssetBundle.LoadFromStream，通过名字就可以知道它是流加载，那么就不会像AssetBundle.LoadFromMemory那样多占一份很大的内存了。
打包Assetbundle的同时生成加密文件的两个文件分别加载它。
myab.unity3d
encypt_myab.unity3d
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[MenuItem("Tools/BuildAB")]
static void BuildAB()
{
FileUtil.DeleteFileOrDirectory(Application.streamingAssetsPath);
Directory.CreateDirectory(Application.streamingAssetsPath);
var manifest = BuildPipeline.BuildAssetBundles(Application.streamingAssetsPath, BuildAssetBundleOptions.ChunkBasedCompression | BuildAssetBundleOptions.ForceRebuildAssetBundle, BuildTarget.iOS);
foreach (var name in manifest.GetAllAssetBundles())
{
var uniqueSalt = Encoding.UTF8.GetBytes(name);
var data = File.ReadAllBytes(Path.Combine(Application.streamingAssetsPath, name));
using (var myStream = new MyStream(Path.Combine(Application.streamingAssetsPath, "encypt_" + name),FileMode.Create))
{
myStream.Write(data, 0, data.Length);
}
}
AssetDatabase.Refresh();
}
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这里测试的Assetbundle一共有20M， 使用LZ4压缩格式。
加密和解密我这里随便写个简单的异或 ^ 。后面也可以用一些更好的算法，总之加密可以慢，但是解密一定要快。
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using System.IO;
public class MyStream : FileStream
{
const byte KEY = 64;
public MyStream(string path, FileMode mode, FileAccess access, FileShare share, int bufferSize, bool useAsync) : base(path, mode, access, share, bufferSize, useAsync)
{
}
public MyStream(string path, FileMode mode) : base(path, mode)
{
}
public override int Read(byte[] array, int offset, int count)
{
var index = base.Read(array, offset, count);
for (int i = 0 ; i < array.Length; i++)
{
array[i] ^= KEY;
}
return index;
}
public override void Write(byte[] array, int offset, int count)
{
for (int i = 0; i < array.Length; i ++)
{
array[i] ^= KEY;
}
base.Write(array, offset, count);
}
}
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界面上放两个Image 分别加载它。
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using System.IO;
using UnityEngine;
using UnityEngine.UI;
public class TestStream : MonoBehaviour
{
[Header("是否启用Stream加载")]
public bool isStream = true;
float m_LoadTime ;
void Start()
{
if (isStream)
{
float t = Time.realtimeSinceStartup;
using (var fileStream = new MyStream(Application.streamingAssetsPath + "/encypt_myab.unity3d", FileMode.Open, FileAccess.Read, FileShare.None, 1024 * 4, false))
{
var myLoadedAssetBundle = AssetBundle.LoadFromStream(fileStream);
m_LoadTime = Time.realtimeSinceStartup - t;
GetComponent<Image>().sprite = myLoadedAssetBundle.LoadAsset<Sprite>("1");
myLoadedAssetBundle.Unload(false);
}
}
else
{
float t = Time.realtimeSinceStartup;
var myLoadedAssetBundle = AssetBundle.LoadFromFile(Application.streamingAssetsPath + "/myab.unity3d");
m_LoadTime = Time.realtimeSinceStartup - t;
GetComponent<Image>().sprite = myLoadedAssetBundle.LoadAsset<Sprite>("1");
myLoadedAssetBundle.Unload(false);
}
}
private void OnGUI()
{
if (isStream)
{
GUILayout.Label(string.Format("<size=50>
AssetBundle.LoadFromStream :{0} </size>", m_LoadTime));
}
else
{
GUILayout.Label(string.Format("<size=50>AssetBundle.LoadFromFile :{0} </size>", m_LoadTime));
}
}
}
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如下图所示，在iPhone7上，基本上加载时间差不多。
加密以后资源就无法被打开了。
注意：Android下的streamingAssets目录不能使用，因为android下是放在jar里并不是文件系统。一定要用的话需要拷贝到 Application.persistentDataPath下。