Using unity app how to read the asset in android SDCard?

I am trying to read one file from my android sd card from my unity application, but its not reading.

using the asset bundle i have exported my file and kept in my android device sd card and i am trying to fetch it and show into my scene.

Here is the code i have used for this:

Code (csharp):

1.  
2. public string URL;
3. public string URLAndroid=Application.persistentDataPath+/cube.unity3d;publicstringAssetName;
4. private string path;
5.  
6. IEnumeratorStart(){
7.  
8. //path = System.IO.Path.Combine (Application.persistentDataPath, "/cube.unity3d");
9.  
10. // Download the file from the URL. It will not be saved in the Cache
11. using(WWW www = WWW.LoadFromCacheOrDownload(URLAndroid,1))
12. {
13. yieldreturn www;
14.  
15. if(www.error !=null)
16. thrownewException("WWW download had an error:"+ www.error);
17.  
18. AssetBundle bundle = www.assetBundle;
19.  
20. if(AssetName=="")
21. Instantiate(bundle.mainAsset);
22. else
23. Instantiate(bundle.LoadAsset(AssetName));
24.  
25. // Unload the AssetBundles compressed contents to conserve memory
26. bundle.Unload(false);
27.  
28. }// memory is freed from the web stream (www.Dispose() gets called implicitly)}
29.  

Here i have used the URLAndroid as a normal downloading method and i have tried to fetch the model using system.io method but its not happening. I have created the corresponding folder in my android device and kept my assets eventhough its not happening.

Plesae help me to solve this issue.

 

any chance to read and get the asset bundle file from android sd card?