private static string GetAndroidExternalFilesDir()
{
     using (AndroidJavaClass unityPlayer = new AndroidJavaClass("com.unity3d.player.UnityPlayer"))
     {
          using (AndroidJavaObject context = unityPlayer.GetStatic<AndroidJavaObject>("currentActivity"))
          {
               // Get all available external file directories (emulated and sdCards)
               AndroidJavaObject[] externalFilesDirectories = context.Call<AndroidJavaObject[]>("getExternalFilesDirs", null);
               AndroidJavaObject emulated = null;
               AndroidJavaObject sdCard = null;
 
               for (int i = 0; i < externalFilesDirectories.Length; i++)
               {
                    AndroidJavaObject directory = externalFilesDirectories[i];
                    using (AndroidJavaClass environment = new AndroidJavaClass("android.os.Environment"))
                    {
                        // Check which one is the emulated and which the sdCard.
                        bool isRemovable = environment.CallStatic<bool ("isExternalStorageRemovable", directory);
                        bool isEmulated = environment.CallStatic<bool> ("isExternalStorageEmulated", directory);
                        if (isEmulated)
                            emulated = directory;
                        else if (isRemovable && isEmulated == false)
                            sdCard = directory;
                    }
               }
               // Return the sdCard if available
               if (sdCard != null)
                    return sdCard.Call<string>("getAbsolutePath");
               else
                    return emulated.Call<string>("getAbsolutePath");
            }
      }
}