DownLoadManager[20530:228829] DiskImageCache: Could not resolve the absolute path of the old directory.

uiwebview 模拟器打开PDF文件时崩溃。报下面错误，还不知道为什么

DownLoadManager[20530:228829] DiskImageCache: Could not resolve the absolute path of the old directory.

但是在真机调试是正常的。