Getting it through the content resolver is the right thing. Not every content url is going to be a file. For example, the Gallery app will give you uri's that translate to a network call or a local file depending on the source.
Even if you'd get to the real file path, you'll probably unable to read it, due to file permissions, although you can be lucky it it's on external storage. Have you tried adding That won't work, since the permission is at signature level :(android.permission.ACCESS_ALL_DOWNLOADS
to your app like the exception suggests?