Google Maps Android指向多边形

Question

I creating a android app that uses google maps android api.
This app need to to have a on click polygon function, but since it not available on google maps android api v2. I did some research and found a work around for this function.
What i ended up with is to check if a point is in a polygon method.
I'm using this library . And it work pretty well if you create the bounds manually.
If can create the bounds in a loop that would solve my problem.
I get the polygon points from my database.

Here is my MapFragment code:

public class MapBlocksMapView extends Fragment {

    protected GoogleMap googleMap;
    protected LatLng latLng;
    protected Intent intent;
    protected String color, crops, block_code, tmp_user;

    public MapBlocksMapView() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        ActionBar actionBar = getActivity().getActionBar();
        actionBar.setTitle("Block View");
        View rootView = inflater.inflate(R.layout.fragment_blocksmapview, container, false);

        if (googleMap== null) {
            googleMap= ((SupportMapFragment) getChildFragmentManager().findFragmentById(R.id.map)).getMap();
        }

        Bundle bundle = getArguments();
        if (bundle != null) {
            block_code = bundle.getString("block_code");
            tmp_user = bundle.getString("user");
        }

        googleMap.setOnMapClickListener(new GoogleMap.OnMapClickListener() {
            @Override
            public void onMapClick(LatLng latLng) {
                checkpoint(latLng.latitude, latLng.longitude);
            }
        });
        return rootView;

    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState){
        getdata(getActivity(), block_code);
        super.onActivityCreated(savedInstanceState);
    }

    private void checkpoint(double latitude, double longitude) {

        System.out.println(latitude +"," +longitude);
    }

    public void getdata(Context ctx, String block_code) {

        SQLHelper dbhelper = new SQLHelper(ctx);
        dbhelper.getReadableDatabase();

        JSONArray jsonArray = dbhelper.getSingleBlocks(block_code);

        try {
            for (int a = 0; a < jsonArray.length(); a++) {

                JSONObject jsonObject = new JSONObject(String.valueOf(jsonArray.getJSONObject(a)));
                JSONArray jsonArray1 = jsonObject.getJSONArray("b_points");
                if (jsonObject.getJSONArray("b_points").length() > 0) {
                    color = jsonObject.getString("b_color");
                    crops = jsonObject.getString("b_crop");
                    PolygonOptions rectOptions = new PolygonOptions();

                    for (int b = 0; b < jsonArray1.length(); b++) {
                        JSONArray jsonArray2 = jsonArray1.getJSONArray(b);

                        rectOptions.add(new LatLng(jsonArray2.getDouble(0), jsonArray2.getDouble(1)));


                        System.out.println(jsonArray2.get(0) + " / " + jsonArray2.get(1));

                    }
                    latLng = new LatLng(jsonArray1.getJSONArray(0).getDouble(0), jsonArray1.getJSONArray(0).getDouble(1));
                    rectOptions.strokeWidth(1).strokeColor(Color.parseColor(color)).fillColor(Color.parseColor(color));
                    googleMap.addPolygon(rectOptions);
                    CameraUpdate cameraPosition = CameraUpdateFactory.newLatLngZoom(latLng, 17);
                    googleMap.animateCamera(cameraPosition);

                } else {

                    Toast.makeText(getActivity(), "Error with the selected block", Toast.LENGTH_LONG).show();
                    closeFragment();
                }
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }

    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        SupportMapFragment f = (SupportMapFragment) getFragmentManager()
                .findFragmentById(R.id.map);
        if (f != null)
            getFragmentManager().beginTransaction().remove(f).commit();
    }

    private void closeFragment() {
        getActivity().getFragmentManager().popBackStack();
    }

}

Here is the example code from the library:

Polygon polygon = Polygon.Builder()
    .addVertex(new Point(1, 3))
    .addVertex(new Point(2, 8))
    .addVertex(new Point(5, 4))
    .addVertex(new Point(5, 9))
    .addVertex(new Point(7, 5))
    .addVertex(new Point(6, 1))
    .addVertex(new Point(3, 1))
    .build();

Point point = new Point(4.5f, 7);
boolean contains = polygon.contains(point);

If some have a other solution or suggestions would be helpful.
Thanks

Answer 1

I also had the same problem but i haven't found a "good" solution for this issue.

In the end i saved all polygons in a list and iterate through it with the click position. (but beware; maybe you have more than a single polygon at this position)

Answer 2

well this that library isnt going to be much help because you have geographical positions and the library expects screen positions so you are going to be doing most of the work yourself really.

you need to take each latlng and convert them into screen points by getting the maps projection

Point point = googleMap.getProjection().toScreenLocation(myLatLngPoint);

then you can put that point into your library like you need when looping. However I do not know what will be returned if the latlng you are using is not in the projection (ie. off the screen) so you will have to test that

Answer 3

I manage to solve this after some digging around and found this code on github.
I'm using this library now and it works like a charm.

My polygon points are stored like this in my database as string.

[[3.65E-4,-1.1E-5],[-5.0E-6,3.54E-4],[-3.0E-6,-1.1E-4]]

Here is a example code

protected double[] points;

public void getdata(){

    SQLHelper dbhelper = new SQLHelper(ctx);
    dbhelper.getReadableDatabase();

    String[] ls =dbhelper.getSingleBlocksPointsArray(block_code)
                .replaceAll("\\[", "")
                .replaceAll("\\]","")
                .split(",");
    points = new double[ls.length];
    for(int i=0;i<ls.length;i++)
    {

        points[i] = Double.parseDouble(ls[i]);
    }
}

in onCreateView i use this:

googleMap.setOnMapClickListener(new GoogleMap.OnMapClickListener() {
    @Override
    public void onMapClick(LatLng latLng) {
        if(contains(new Coordinate(latLng.latitude,latLng.longitude), points)) {
            Toast.makeText(getActivity(),"True",Toast.LENGTH_SHORT).show();
        }else {
            Toast.makeText(getActivity(),"False",Toast.LENGTH_SHORT).show();
        }
    }
});