Question

I have profiles in my mobile app and in web project. We are currently thinking about how can we synchronize them. The point is, if person add something to mobile profile – we can just send a bundle of ids to webserver and server will add them as well. The same with removing items. But what is if person will removes in mobile profile without constant connection, then removes something inside his profile in webserver`s profile? And after that we have to synchronize it somehow.

I understand that solution of such issue has to be already found, but unfortunately I didn`t find anything helpful yet.

Answer 1

I’d recommend watching Virgil Dobjanschi’s Google I/0 2010 talk on designing RESTful client applications: here. It’s about an hour long, but very informative and helpful.

Some key points to note are:

• Use a SQLite database to act as a cache between your application and the webserver, so changes can be saved even there is no connection, then sent/received once you gain connection again.
• Use a Service to handle REST calls, as it won’t be restricted by a single Activity’s lifecycle. This way your server requests can still be executed and properly handled if a user or the Android OS kills your Activity, a phone call pushes your application off the screen, etc. I’m using an Intent Service, as it handles threading for you.

You also need to determine which syncing relationship is most suitable for your application. What I mean by that is “Which database should overwrite the other: The SQLite or the webserver?”. So when there are differences between the two, which data should be deemed “correct”? This is commonly referred to as master-slave.