Android object handling / persistence

Question

I am pretty far into my first Android application, and I have the sneaking suspicion that I'm "Doing It Wrong". My app talks to a Ruby on Rails server and serializes objects back and forth via XML. Before I knew what was happening, I found myself knee deep in writing my own crappy ORM, a problem which is compounded by the fact that I haven't written any Java since high school.

My conflict here is that I want my client-side (android) app to be capable of serializing via a variety of methods, such as HTTP/XML, to a local database, or out to the local filesystem. I started out with the Strategy pattern, but I feel like my solution is badly lacking.

For one, should I re-implement all of Rails model validation on the client side, because I don't know if I'm always going to be working with Rails on the other side? The even bigger issue is that right now I can only represent flat objects as key-values, as my code can't handle nested objects like a true ORM.

I'm sure Android devs deal with this all the time, so I'm interested to hear what other people do to cope with these issues.

Answer 1

I wouldn't approach your Android application as an extension of a Ruby app - rather a consumer of an API. If you can try to expose your server application as JSON (or other format, but JSON is the most lightweight) and consume these APIs from your Android application you would most likely have less problems as JSON is already in K/V format.

I have not yet written Android objects to SQLite yet, but I have written them as both Parcelable objects and to the SharedPreferences. Both of these strategies are sufficient for small to mid-range apps. For data intensive apps, obviously you will have to take it a step further to SQLite.

There are some great articles for these approaches: Managing State.

It boils down to designing your objects in a way that can be serialized easily. That means no circular references or extremely complex objects. This shouldn't be a very large problem, especially if your data is in JSON format already. You simply need to extend some classes and add functions that return a Parcelable object representation or a string representation so your objects can be saved thus.

I would avoid cloning your server-side objects and validation in Android as it then requires modifying both sources if you make small changes. The server should handle all data and validation and you should simply be requesting, caching, and sending data from Android.

I'd be interested to hear if there any challenges to writing objects to SQLite, but I imagine it's not that much more of step from the details I've outlined above. Hope this helps in some capacity!

Answer 2

I think you might be going too heavy for a smart phone application. I would look at using RESTful style web services with JSON content.

Answer 3

I haven't done much of persistence storage on Android but I think you need to use SQLiteDatabase and make your own Cusor that De/Serializes your object so that it can be added to the database. A possible solution would be to extend a SQLiteCursor or an AbstractCursor.

Otherwise I don't think there is other solution apart from, possibly, "hardcore" Serializabled (Which I suspect it may be too much for a phone, I may be wrong)