Where to save Android GPS (Latitude , Longitude) points?

Question

On onLocationChanged event I want to save my GPS route (Latitude , Longitude). Later I want to load this data and draw the route.

Who is the best way to do this, by using some array type (and save or load by using database) or XML files or something else?

Thanks.

Answer 1

The best way of storing double values in SharedPreferences without losing precision is:

• Transform to bit representation to store it as long:

  prefsEditor.putLong("Latitude", Double.doubleToLongBits(location.getLatitude()));
  

• To retrieve, transfrom from bit representation to double:

  double latitude = Double.longBitsToDouble(prefs.getLong("Latitude", 0);
  

However, I think that if you want to store a big amount of points is better using a SQLite database than saving each coordinate in a Key-Value pair in SharedPreferences or serialize the array in XML and write it to a file or to SharedPreferences. The database offers you the advantage of loading in memory only the points within the area you are displaying in the map, so you can save memory.

Answer 2

Correct me if I'm wrong, but it might be better to convert the double values to strings and then whenever you call them convert them back to doubles. Sounds like a pain, but oracle's website (http://download.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html) says:

"use a float (instead of double) if you need to save memory in large arrays of floating point numbers. This data type should never be used for precise values, such as currency"

prefEditor.putString("Latitude", Double.valueOf(loc.getLatitude()).toString());

Then, to call the value

String latitudeString = pref.getString("Latitude", "0");
double latitude = Double.parseDouble(latitudeString);

It definitely seems like more of a nuisance, but seems also more likely to return the exact value that you saved, also, instead of something slightly off. And I suppose that would depend on how completely accurate you need the values to be.

Though, as far as using an array, I'm clueless because I've never needed to use them and have no experience with them.