Access raw AssetBundle data using UnityWebRequest?

Questions & Answers
1

Following Unity’s advice, starting Unity 5.3, it is strongly recommended to use UnityWebRequest -rather than WWW.LoadFromCacheOrDownload- to download AssetBundles from a server. However, we also need to store the downloaded bundles locally (via Application.persistentDataPath)… but how??

WWW.LoadFromCacheOrDownload provides you with a byte[] that could be saved/loaded. Unfortunately, accessing the data field in DownloadHandlerAssetBundle is not allowed and triggers an exception. Is there any way to access/save the downloaded data using UnityWebRequest? Or are we forced to go back and use WWW.LoadFromCacheOrDownload instead?

PS - We are aware of the Caching functionality, but we want to store it locally.

2

Hi, @chico_barnstorm.

I think that what you are looking for is:

wwww.downloadHandler.data
3

Hi,
this seems to work:

string url = "http://myserver.com/myassetBundle";
UnityWebRequest www = UnityWebRequest.Get(url);
yield return www.Send();
    
string filePath = Path.Combine(Application.persistentDataPath, "myassetBundle");
File.WriteAllBytes(filePath, www.downloadHandler.data);
    
AssetBundle bundle = AssetBundle.LoadFromFile(filePath);

It is a raw code, you need to write validations…

4

If you’re using DownloadHandlerAssetBundle, your AssetBundle data will probably be cached locally by Unity automatically. Since you want to access the raw binary data, I assume that you’re implementing your own AssetBundle cache system and want to bypass Unity’s implementation.

Then you will have to write your own DownloadHandlerScript like this:

class CustomAssetBundleDownloadHandler : DownloadHandlerScript
{
    private string _targetFilePath;
    private Stream _fileStream;

    public CustomAssetBundleDownloadHandler(string targetFilePath)
        : base(new byte[4096]) // use pre-allocated buffer for better performance
    {
        _targetFilePath = targetFilePath;
    }

    protected override bool ReceiveData(byte[] data, int dataLength)
    {
        // create or open target file
        if (_fileStream == null)
        {
            _fileStream = File.OpenWrite(_targetFilePath);
        }

        // write data to file
        _fileStream.Write(data, 0, dataLength);

        return true;
    }

    protected override void CompleteContent()
    {
        // close and save
        _fileStream.Close();
    }
}

When you need to download a file, just create a new CustomAssetBundleDownloadHandler(pathToFile), assign it to the UnityWebRequest object as its download handler, and data will be saved to the target file.

5

i think you can download ab as a file and save it on local then load it OK?