How to Cache AssetBundle to the SDCard

Unity Engine
1

I’m using AssetBundle on Android platform,and I met some problems in caching bundles to the sdcard.

I found when I add the write_external_storage,and mount_unmount_filesystems permission,Unity will automatically cache bundles to sdcard when i use LoadfromCachOrDownload,but when i run the app again,I can’t load bundles from cache successfully.If i delete the permission,the cache will be saved to the internal storage,and everything will be ok.

Witch is the right way to save cache to external storage?

2

This problem will not appear every time.Some times it will be ok,some times i would receive an exception:" Cannot load cached AssetBundle.A file of the same name is already loaded from another AssetBundle. " But I’m sure it’s my first time to load AssetBundle,no other bundles would be loaded before this file.