Hello. Why not include support for WebDAV? Then it would be possible to synchronize the selected folder with WebDAV server. I own a home server with OwnCloud and found that there are no Free and Open source applications on Android, with which I could sync my files. If you enjoy my idea, I can help in the implementation of this functionality.
We have thought about that ourselves, and find it an interesting and challenging task. After some thoughts, we have found several reasons why it would be better to make a separate app for WebDAV file synchronization. The algorithms are quite different, but the dav4android library could be reused.
Unfortunately, file synchronization is much more complex and error-prone (because of conflicts where we don't have the stateful information like we have it from the Contacts and Calendar Providers), but it should be possible.
Also, there are some challenges and caveats: for instance, file transfers would have to be resumble, and as far as I know, there's no way to resume
PUTrequests (= file uploads). The newer
PATCHmethod is not always supported and has some disadvantages.