AssetBundles

【AssetBundles】

　　AssetBundles can express dependencies between each other; e.g. a material in AssetBundle A can reference a texture in AssetBundle B. For efficient delivery over networks, AssetBundles can be compressed with a choice of built-in algorithms depending on use case requirements (LZMA and LZ4).

　　AssetBundles can be useful for downloadable content (DLC), reducing initial install size, loading assets optimized for the end-user’s platform, and reduce runtime memory pressure.

　　Note that AssetBundle names do support a type of folder structure depending on what you type. To add sub folders, separate folder names by a “/”. For example: AssetBundle name “environment/forest” will create a bundle named forest under an environment sub folder.

1、添加一个菜单选项，以来Build AssetBundle。

　　When you click Build AssetBundles a progress bar will appear with a build dialogue. This will take all the assets you labeled with an AssetBundle name in and place them in a folder at the path defined by assetBundleDirectory.

using UnityEditor;

public class CreateAssetBundles
{
    [MenuItem("Assets/Build AssetBundles")]
    static void BuildAllAssetBundles()
    {
        string assetBundleDirectory = "Assets/AssetBundles";
        if(!Directory.Exists(assetBundleDirectory)
{
    Directory.CreateDirectory(assetBundleDirectory);
}
BuildPipeline.BuildAssetBundles(assetBundleDirectory, BuildAssetBundleOptions.None, BuildTarget.Standalone);
    }
}

 2、通过 LoadFromFile 加载AssetBundle。

public class LoadFromFileExample extends MonoBehaviour {
    function Start() {
        var myLoadedAssetBundle = AssetBundle.LoadFromFile(Path.Combine(Application.streamingAssetsPath, "myassetBundle"));
        if (myLoadedAssetBundle == null) {
            Debug.Log("Failed to load AssetBundle!");
            return;
        }
        var prefab = myLoadedAssetBundle.LoadAsset.<GameObject>("MyObject");
        Instantiate(prefab);
    }
}

3、使用UnityWebRequest下载，并使用DownloadHandlerAssetBundle来加载。

　　GetAssetBundle(string, int) takes the uri of the location of the AssetBundle and the version of the bundle you want to download.

　　The UnityWebRequest has a specific handle for dealing with AssetBundles, DownloadHandlerAssetBundle, which gets the AssetBundle from the request.

IEnumerator InstantiateObject()

    {
        string uri = "file:///" + Application.dataPath + "/AssetBundles/" + assetBundleName;        
        UnityEngine.Networking.UnityWebRequest request = UnityEngine.Networking.UnityWebRequest.GetAssetBundle(uri, 0);
        yield return request.Send();
        AssetBundle bundle = DownloadHandlerAssetBundle.GetContent(request);
        GameObject cube = bundle.LoadAsset<GameObject>("Cube");
        GameObject sprite = bundle.LoadAsset<GameObject>("Sprite");
        Instantiate(cube);
        Instantiate(sprite);
    }

【使用AssetBundle】

1、通过加密AssetBundle内的内容，来保护数据。

string url = "http://www.mywebsite.com/mygame/assetbundles/assetbundle1.unity3d";
IEnumerator Start () {
    // Start a download of the encrypted assetbundle
    WWW www = new WWW.LoadFromCacheOrDownload (url, 1);

    // Wait for download to complete
    yield return www;

    // Load the TextAsset from the AssetBundle
    TextAsset textAsset = www.assetBundle.Load("EncryptedData", typeof(TextAsset));
 
    // Get the byte data
    byte[] encryptedData = textAsset.bytes;

    // Decrypt the AssetBundle data
    byte[] decryptedData = YourDecryptionMethod(encryptedData);

    // Use your byte array. The AssetBundle will be cached
}

2、通过加密AssetBundle，来保护数据。

string url = "http://www.mywebsite.com/mygame/assetbundles/assetbundle1.unity3d";
IEnumerator Start () {
    // Start a download of the encrypted assetbundle
    WWW www = new WWW (url);

    // Wait for download to complete
    yield return www;

    // Get the byte data
    byte[] encryptedData = www.bytes;

    // Decrypt the AssetBundle data
    byte[] decryptedData = YourDecryptionMethod(encryptedData);

    // Create an AssetBundle from the bytes array

    AssetBundleCreateRequest acr = AssetBundle.CreateFromMemory(decryptedData);
    yield return acr;

    AssetBundle bundle = acr.assetBundle;

    // You can now use your AssetBundle. The AssetBundle is not cached.
}

3、一个AssetBundle中加入另一个加密过的AssetBundel。

string url = "http://www.mywebsite.com/mygame/assetbundles/assetbundle1.unity3d";
IEnumerator Start () {
    // Start a download of the encrypted assetbundle
    WWW www = new WWW.LoadFromCacheOrDownload (url, 1);

    // Wait for download to complete
    yield return www;

    // Load the TextAsset from the AssetBundle
    TextAsset textAsset = www.assetBundle.Load("EncryptedData", typeof(TextAsset));
 
    // Get the byte data
    byte[] encryptedData = textAsset.bytes;

    // Decrypt the AssetBundle data
    byte[] decryptedData = YourDecryptionMethod(encryptedData);

    // Create an AssetBundle from the bytes array
    AssetBundleCreateRequest acr = AssetBundle.CreateFromMemory(decryptedData);
    yield return acr;

    AssetBundle bundle = acr.assetBundle;

    // You can now use your AssetBundle. The wrapper AssetBundle is cached
}

4、二进制数据必须以.bytes结尾，才能保存进AssetBundle，类型是TextAsset。

string url = "http://www.mywebsite.com/mygame/assetbundles/assetbundle1.unity3d";
IEnumerator Start () {
    // Start a download of the given URL
    WWW www = WWW.LoadFromCacheOrDownload (url, 1);

    // Wait for download to complete
    yield return www;

    // Load and retrieve the AssetBundle
    AssetBundle bundle = www.assetBundle;

    // Load the TextAsset object
    TextAsset txt = bundle.Load("myBinaryAsText", typeof(TextAsset)) as TextAsset;

    // Retrieve the binary data as an array of bytes
    byte[] bytes = txt.bytes;
}

5、只能加载一个同名AssetBundle。

6、AssetBundle.LoadAssetAsync。

using UnityEngine;

// Note: This example does not check for errors. Please look at the example in the DownloadingAssetBundles section for more information
IEnumerator Start () {
    // Start a download of the given URL
    WWW www = WWW.LoadFromCacheOrDownload (url, 1);

    // Wait for download to complete
    yield return www;

    // Load and retrieve the AssetBundle
    AssetBundle bundle = www.assetBundle;

    // Load the object asynchronously
    AssetBundleRequest request = bundle.LoadAssetAsync ("myObject", typeof(GameObject));

    // Wait for completion
    yield return request;

    // Get the reference to the loaded object
    GameObject obj = request.asset as GameObject;

        // Unload the AssetBundles compressed contents to conserve memory
        bundle.Unload(false);

        // Frees the memory from the web stream
        www.Dispose();
}

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