Generating and storing a random, unique user id to track unique installations of an android app.

UniqueId.java

// adaptation of: http://android-developers.blogspot.com/2011/03/identifying-app-installations.html
// but using shared preferences instead of a file: http://developer.android.com/reference/android/content/SharedPreferences.html
// here's a better look at using shared preferences: http://developer.android.com/guide/topics/data/data-storage.html#pref

public class UniqueId {

	private static String sID = null;
	private static final String SHARED_PREF_KEY = "SKETCHABIT2";
	private static final String ID_KEY = "id";

	public synchronized static String id(Context context) {
		if (sID == null) {
			SharedPreferences pref = context.getSharedPreferences(
					SHARED_PREF_KEY, 0);
			
			sID = pref.getString(ID_KEY, "");

			if (sID == "") {
				sID = generateAndStoreUserId(pref);
			}

		}
		return sID;
	}

	private synchronized static String generateAndStoreUserId(SharedPreferences pref) {
		String id = UUID.randomUUID().toString();
		SharedPreferences.Editor editor = pref.edit();
		editor.putString(ID_KEY, id);
		editor.commit();
		return id;
	}
	
}