Best way to figure out which regions a point is in a shapefile?

Question

I'm trying to figure out the best way on Android to figure out if a point in region as defined in a shapefile. For instance, I might want to know what country I'm in using the Geo Common's Shapefile file for Countries. Is there an existing Android library that can manage such tasks with Shapefiles, or an equivalent substitute (KML, for instance)? A few other points:

1. I might be using a lot of regions. For instance, I might want to know what county I'm in, along with state and country. Thus, there is potential for overlap of regions.
2. Speed is desirable, if possible. I might, for instance, figure out which country I'm in, then state, then county, and only look at the applicable states for a country, and counties for a state.
3. Compactness is very important. At least one of the data files I want to work with is 47 Mb as a KML, Shapefiles seems like a reasonable size, assuming I can find a decent library for it.

Answer 1

I will suggest that you use SpatiaLite in your Android Application to store the Countries Data.

There is a loader with a GUI available for loading your shapefile into the SpatiaLite Database.

Once your data in inside the database, you can do spatial queries directly from your Android Application. The Spatialite Tutorial has some examples on how you can query the database.

The following code will show how you can do this:

//AppBase is a folder
File SpatialDBFile=new File(AppBase, "gdb.sqlite");
if(SpatialDBFile.exists())
{
   jsqlite.Database db = new jsqlite.Database();
  db.open(SpatialDBFile.getAbsolutePath(),
                jsqlite.Constants.SQLITE_OPEN_READWRITE);


String query="select objectId, name, AsText(Geometry) from countries where 
 Within(MakePoint("+longitude.toString()+ ", "+ latitude.toString() +"), Geometry)=1;";

    try{
        Stmt statement=db.prepare(query);
        while(statement.step())
        {
            String name=statement.column_string(1); 
            //do whatever you need to do with this name
        }
    }catch (Exception e){
        //handle the exception
    }
    db.close();
}

Answer 2

Seems like you need:

1. point-in-polygon feature for android. For this you may want to find good client library for mapping. This post has some good ideas: Is there an comparison of the various mapping libraries for Android? If you want to write your own point-in-poly, there are a bunch of examples out there including: https://stackoverflow.com/questions/11716268/point-in-polygon-algorithm

2. shapefile to android interface. You may find that shapefile is not the most convinent way to store your data. I would recommend looking at geojson as a storage format instead of shapefile because its simpler file structure, and a standard web protocol. https://stackoverflow.com/questions/18445191/android-google-map-polygon-click-event

Are you using any mapping client library for Android?