In the last few weeks the battle and buzz over the smart phone market seems to have seriously intensified.
First there was the usual iPhone buzz, news about the Android powered HTC Magic, the Windows Mobile marketplace, and of course the obligatory ridiculousness at Microsoft.
I’d been considering experimenting with a mobile platform for sometime and finally decided to take the plunge. I decided to give Android a whirl primarily because I don’t have easy access to OSX or Visual Studio and my Java is less rusty than my .NET.
Anyway, getting going with Android was deliciously simple - download the SDK+Emulator and Eclipse plugin and you’re off.
After the necessary “Hello World” application I tried to write something a bit more substantive. Personally, one of the coolest facets of mobile development is the ability for applications to be location aware (GPS). Mix this together with some openly available geo tagged data and the result is probably going to be interesting.
With this in mind, the plan became to mash together Android’s GPS coordinates with flickr’s geotagged photos.
Getting access to Android’s location service is fairly straightforward. You basically register to receive updates either when the device moves a certain distance or on some time interval:
LocationManager locationManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
flickrLocationReciever flReciever = new flickrLocationReciever();
locationManager.requestLocationUpdates( locationManager.getProviders(true).get(0), 5, 10, flReciever);
public class flickrLocationReciever implements LocationListener {
@Override
public void onLocationChanged(final Location arg0) {
// do things
}
}
The biggest “gotcha” with this is that you NEED to remember to modify the default Application security settings to allow you to access the device’s location. In Eclipse, edit AndroidManifest.xml and add “UsesPermission” for the following: android.permission.ACCESS_MOCK_LOCATION, android.permission.ACCESS_COARSE_LOCATION, android.permission.ACCESS_FINE_LOCATION
So on to part II - using the device’s location to pull down Flickr photos. I’d used the Flickr API before so I knew how to do it but I’d never used it from Java. I tried loading the JAR for the flickrj client library but the Android JVM was having some strange issues with it. I was under the impression you can link to external JARs from Eclipse but I may be wrong (anyone?).
Anyway, the Flickr requests were un-authenticated and pretty straightforward so I decided to use Java’s URL class. Accessing sockets was another “gotcha” - Android requires your application to have the “UsesPermission” android.permission.INTERNET to use sockets. The exception when the permission isn’t set is notably cryptic - “unknown error”.
I decided to download all the Flickr photos to the device so that the UX would be generally smoother. This introduced threading to the project so that the UI wouldn’t freeze up while the photos were downloading. Android threads work just like traditional Java threads and the process was generally painless:
private Handler handler = new Handler()
{
public void handleMessage(Message msg) {
// handle the end of the thread
}
}
Thread t = new Thread()
{
public void run(){
// do stuff
// let the handler know we are done
handler.sendEmptyMessage(1);
}
}
T.start();
With the photos pulled down the final task was displaying them. After poking around the Android documentation I discovered the Gallery widget. It basically allows you to display a set of items in a list and specify a “renderer” for the gallery. I’m not sure if there is a default way to make it “fisheye” (like on an iPhone) but I rolled a quick n dirty solution for that. I also couldn’t get it to look really sexy but that’s also probably possible.
So that’s about it. Here are some screen shots of the application running in the emulator:
And without further a due here is the code as an Eclipse project.
geoflickr
Anyway, before the bashing starts - I know I’m a terrible Java programmer and that this project isn’t really engineered beautifully. It was just supposed to be a way to get my (and anyone else’s) feet wet with Android. Any comments/thoughts/improvements are of course welcome!
