DownloadHandlerAssetBundle.GetContent returns null for StreamingAsset

We're still struggling to migrate our project to AssetBundles. One big roadblock is the unpredictability of simply loading assets from the normal channels (UnityWebRequest.GetAssetBundle and DownloadHandlerAssetBundle.GetContent).

Our game is a mobile game on iOS and Android, and we utilize StreamingAssets to pre-populate AssetBundles in our binary. The code to load, for example, the iOS manifest file, is simply this:

Code (CSharp):

1. string bundleName = "iOS";
2.  
3. string basePath = Path.Combine((Application.platform == RuntimePlatform.Android ? "" : "file://") + Application.streamingAssetsPath, PlatformUtils.RuntimePlatformIdentifier);
4. string bundlePath = Path.Combine(basePath, bundleName);
5.  
6. // We generate a Hash128 instance with random values in each section so the system doesn't attempt to cache the platform manifest
7. UnityWebRequest request = UnityWebRequest.GetAssetBundle(bundlePath, randomHash, 0);
8. UnityWebRequestAsyncOperation operation = request.SendWebRequest();
9.  
10. yield return operation;
11.  
12. if(operation.webRequest.isHttpError || operation.webRequest.isNetworkError || !string.IsNullOrEmpty(operation.webRequest.error))
13. {
14.     throw new Exception(string.Format("Failed to load AssetBundle from StreamingAssets. bundleName={0}, bundlePath={1}, isHttpError={2}, isNetworkError={3}, responseCode={4}, error={5}",
15.         bundleName, bundlePath, operation.webRequest.isHttpError, operation.webRequest.isNetworkError, operation.webRequest.responseCode, operation.webRequest.error));
16. }
17.  
18. AssetBundle bundle = DownloadHandlerAssetBundle.GetContent(operation.webRequest);
19. if(bundle == null)
20. {
21.     throw new Exception(string.Format("Failed to load AssetBundle from StreamingAssets (GetContent returned null). bundleName={0}, hash={1}, bundlePath={2}",
22.         bundleName, hash, bundlePath));
23. }
24.  

Most of the time, that code runs just fine. However, we're still getting random errors that look like this:

The docs on the GetContent method are woefully unhelpful on the method's function:

Gee, thanks. Is there some reason the method returned null? Maybe the device is out of space when the download handler attempted to copy the file into cache? Was the cache not ready yet? Bueller?

The painful part about this error is that it's one of the very first things that happens during our game, so if a user encounters it, the experience is almost certainly a bad one.

I want to use AssetBundles. We actually reverted to using the Resources folder for everything in a build last week that resulted in 0 errors related to loading files. Unfortunately, we had to go back to AssetBundles because for some reason the same files packed as AssetBundles into the StreamingAssets folder is ~20 MB smaller than the way Unity packs assets in the Resources directory, and Google Play has other annoying "features" (expansion files, ugh) when binaries are above 100 MB.

Any ideas?

P.S. Why does Path.Combine not complain when I'm using its overload that accepts 3 path arguments in my IDE (Rider) but complains in-editor when Unity tries to compile my project? I'm guessing this might be solved by trying to update our .NET profile to 4.6?

P.P.S. Any way to avoid that ugly '(Application.platform == RuntimePlatform.Android ? "" : "file://")' ternary statement? Android builds will prepend 'jar:file://' onto the beginning of Application.streamingAssetsPath, but none of the other platforms append the protocol. For some reason I thought there was work being done to make things "just work" cross-platform when using but I guess there are still special cases.

 

We are experiencing the same behavior inside our UWP project running inside VS2017. Any solution in sight?

 

Nope!

 

@Reichert Has this been fixed? Curious if Assetbundles are production ready.

 

Any solution for this?

 

About the UnityWebRequestAssetBundle.GetAssetBundle() that returns nulls

This is my code. On UnityEditor works, but doesn't in Android 9

Code (CSharp):

1.  using (UnityWebRequest www = UnityWebRequestAssetBundle.GetAssetBundle("my-asset-bundle-url"))
2.             {
3.                 yield return www.SendWebRequest();
4.  
5.                 if (www.isNetworkError || www.isHttpError)
6.                 {
7.                     Debug.Log(wr.error);
8.                 }
9.                 else
10.                 {
11.                     // Get downloaded asset bundle
12.                     AssetBundle bundle = DownloadHandlerAssetBundle.GetContent(www);
13.  
14.                 }
15.             }

 

I built the asset bundle for android. I've debugg the app in my phone and in this line AssetBundle bundle = DownloadHandlerAssetBundle.GetContent(www); returns null. There's no errors.

 

Hi guys,

I have the same experience with the DownloadHandlerAssetBundle.GetContent, it always returns null on some devices.

First of all I have small number of devices, which couldn't load Asset Bundles from Streaming Assets folder. I can see in my console, that loading assets (AssetBundle.LoadFromFileAsync("assets path")) appears to be null.
So I added assets to the server and added code in the app to load them. Everything works fine for all the Android phones.
But some phones (I don't have them, so I can't provide Logcat) show null value, if I check DownloadHandlerAssetBundle.GetContent.
I even made more tests with WWW.LoadFromCacheOrDownload. It has the same experince. Most of devices work good and they are easily loading assets from the server. But some devices return null if I'm trying to load asset: www.assetBundle.

No erros in Fabric, or Firebase Crashlytics, except NullReferenceException, if I'm trying to use assetBundle, which is currently null.
No UnityWebRequest.isNetworkError or UnityWebRequest.isHttpError, no www.error.
Tested with compressed and uncompressed assets bundles. Of course
BuildTarget.Android there used.

 

i need solution for my problem: i clear cache and re-open app without internet connection. How do i save and load asset bundle from local file?

 

I mean when i downloaded Asset Bundle successfully i want to write it into local file. Because i have problem if user clear cache and re-open app without internet connection

 

Thank you very much for your suggestion

 

Not the specific phone models and no specific Android versions.
No caching. Everytime I'm loading new asset, I'm deleting current or cached in memory version. However it happens mostly on application startup and there's no cached in memory assets.

Just simple code:

Code (CSharp):

1. AssetBundleCreateRequest bundleReq = AssetBundle.LoadFromFileAsync(GetBundlesAddress("asset"));

After this code there's check for request == null or assetbundle inside == null. And on some devices I receive logs, that some of these are null.

Code to return AssetBundle address:

Code (CSharp):

1. string GetBundlesAddress (string assetToLoad)
2.     {
3.         string bundlesFolder = "";
4.         if (Application.platform == RuntimePlatform.IPhonePlayer)
5.         {
6.             bundlesFolder = "iosbundles";
7.         } else if (Application.platform == RuntimePlatform.Android)
8.         {
9.             bundlesFolder = "androidbundles";
10.         } else
11.         {
12.             if (Directory.Exists ("Assets/StreamingAssets/iosbundles"))
13.             {
14.                 bundlesFolder = "iosbundles";
15.             } else if (Directory.Exists ("Assets/StreamingAssets/androidbundles"))
16.             {
17.                 bundlesFolder = "androidbundles";
18.             } else
19.             {
20.                 Debug.LogWarning ("NO ASSET BUNDLES!!!");
21.             }
22.         }
23.         return Path.Combine(Application.streamingAssetsPath, bundlesFolder, assetToLoad);
24.     }