Screaming Penguin

So I was one of the speakers at DevNexus 2010. DevNexus is a fairly large (respectively) Atlanta area tech conference that is organized by the folks at AJUG.

Another useful Android programming tip is to either allow users to selectively backup any database your application uses, or just do it for them in the background (at some interval).

Why is this important? Well, if the user gets a new phone (for whatever reason, lost it, upgraded, chucked it out the window before going kayaking) one of the first things they will do is hit the Android Market again and try to re-download the applications they had (the Market saves this info and makes it easy, well, generally, there are a few quirks, but that is beyond the scope here). Also, they might just want to uninstall your app at some point and later come back to it on an existing phone. Without a database backup they might re-acquire your application but they will be pissed (rightly so) if all the data is missing.

Some applications handle this very well (notably Evan Charlton's Mileage, which is a great app BTW, has always upgraded for me flawlessly -- I don't know if it uses a similar method to what I advocate here or not, but it works very well however it does it), and others don't (Google Listen, I am looking at you ;)).

To that end in this article we are going to modify the AndroidExamples application we have worked on before here at TotSP to include a new Activity that allows users to backup the database. This is really just to demonstrate a few ways to do this rather than an exhaustive example, but it should get you started if you are interested in this area.

Our new version of AndroidExamples (complete code via the link) will have a Menu on the Main activity that lets users go to a new ManageData activity -- as seen in the screen shot below:

Programming on Android is pretty easy. At least it is at first, then the subtleties creep in -- like maintaining state, long running tasks, managing orientation changes, and so on. When you get to that stuff programming Android gets, well, not hard, but let's say more complicated.

The Android APIs are generally very nice, and there are ways to deal with just about any situation, it's just that they aren't always obvious. In this tutorial we will expand on the last one we worked on which covered SQLite and using a database. Here we are going to fill out more details, including adding an android.app.Application object to create expensive objects and maintain state, adding a few more data operations, and putting said data operations onto a background Thread using AsyncTask (plus demonstrating saving instance state when the screen orientation is changed, and restoring same).

The complete application, which is intended to be very simple, will look like the screen shot below:

Because I often have to revisit this stuff myself, I thought I would write a quick reference tutorial on creating and using a database with an Android application. This isn't terribly well covered in the Android docs, and though many ContentProvider tutorials exist (such as the Unlocking Android code for chapter 5, and the NotePad tutorial included with the SDK), and these help a lot with general database concepts, they are really more complicated than what a basic application needs - a database to store and retrieve stuff.

I will walk through the code and tools for an oversimplified example here, with the ultimate goal of inserting and retrieving some data from an database in an Android app, and then examining the database using a shell and the sqlite3 command line tool. The entire code for this example is available here: http://totsp.com/svn/repo/AndroidExamples/trunk/.

NOTE This code was updated for part 2, and part 3 of this series, so it no longer exactly matches this example -- it's still a working sample app, it just now does a bit more than the original.

First, to get this rolling, we need to create an Android application that HAS a database. We could use any built in application that has a database just to explore it, such as com.android.alarmclock), but we are going to create one here for completeness. After it's setup, the interface for our application will look like the screen shot shown below:

It has been a while since I have gotten on the soap box, but the way Americans seem to think everything is a "debate" just chaps my hide, so here goes.

Everything is NOT a debate. At least not in the sense that most people that question scientific evidence mean it. Here I am talking about global warming, evolution, vaccines, and every other such fact ignorant people choose not to "believe." It's not about belief jackass, it's about evidence, and science, and frankly, reality.

Here is an excellent video that does a much better job than I can, of explaining what I mean: