Question

I would like to store a Location object and am trying to pick a good way to do it. I just have the one small object, and I need it to be private, so SharedPreferences or Internal Storage make the most sense to me so far.

I see that an object can be written to a bytearray, stored as a String in SharedPreferences, then written back to an object as described here.

Is that a reasonable approach? Is there a better way?

Thanks for any advice.

Answer 1

When saving simple data I prefer using JSON objects as the code is simpler and easier to understand for future maintainers than manipulating byte arrays. Since the objects are small the size penalty for using strings instead of byte arrays is not significant.

private static final String LATITUDE = "com.somepackage.name.LATITUDE";
private static final String LONGITUDE = "com.somepackage.name.LONGITUDE";

/**
 * Save a location/key pair.
 * 
 * @param key the key associated with the location
 * @param location the location for the key
 * @return true if saved successfully false otherwise
 */
public boolean saveLocation(String key, Location location) {
    LOG.info("Saving location");
    try {
        JSONObject locationJson = new JSONObject();

        locationJson.put(LATITUDE, location.getLatitude());
        locationJson.put(LONGITUDE, location.getLongitude());
        //other location data
        SharedPreferences.Editor edit = preferences.edit();
        edit.putString(key, locationJson.toString());
        edit.commit();
    } catch (JSONException e) {
        LOG.error("JSON Exception", e);
        return false;
    }

    LOG.info("Location {}  saved successfully at key: {}", preferences.getString(key, null),key);
    return true;
}

/**
 * Gets location data for a key.
 * 
 * @param key the key for the saved location
 * @return a {@link Location} object or null if there is no entry for the key
 */
public Location getLocation(String key) {
    LOG.info("Retrieving location at key {} ", key);
    try {
        String json = preferences.getString(key, null);

        if (json != null) {
            JSONObject locationJson = new JSONObject(json);
            Location location = new Location(STORAGE);
            location.setLatitude(locationJson.getInt(LATITUDE));
            location.setLongitude(locationJson.getInt(LONGITUDE));
            LOG.info("Returning location: {}" , location);
            return location;
        }
    } catch (JSONException e) {
        LOG.error("JSON Exception", e);
    }

    LOG.warn("No location found at key {}",  key);
    //or throw exception depending on your logic
    return null;
}