I've searched through android's open source code as much as I could and I haven't been able to find the implementation to the actual downloading via the DownloadManager in the 2.3 SDK. I have found the source for the DownloadManager and the source for a download class that has constants to interact with the ContentProvider but I haven't been able to find the source for the ContentProvider.
I'm wanting to find this so that I can know a good way to implement a download of my own, since I'll be using a lesser version than 2.3 for my app.
I was able to find this here. You can also get the project by cloning the DownloadProvider project and looking at the project source code. The DownloadProvider.java specifically was what I was looking for. However, the DownloadThread.java handles the heart of the download implementation, so I would recommend looking at that.
The git command is
git clone https://android.googlesource.com/platform/packages/providers/DownloadProvider
来源：https://stackoverflow.com/questions/5069919/where-can-i-find-downloadmanagers-contentprovider-implementation