Google Maps API - different map style for polygon

问题

I want to achieve the effect similar to what is presented here:

inside Android google map. The polygon should have a different map style (json file) than the rest of the map. Is there a way of doing that? I would even accept having two different maps (one under the other) and cutting the polygon out of the top map. Would that be possible?

回答1:

That effect is possible with Polygon.setHoles() or PolygonOptions.addHole() methods. You should create gray transparent polygon for all map (from -90 to 90 degrees of latitude and from -180 to 180 of longitude) with holes for each of your terrain location. Something like this:

public class MainActivity extends AppCompatActivity implements OnMapReadyCallback {

    private static final String TAG = MainActivity.class.getSimpleName();
    private GoogleMap mGoogleMap;
    private MapFragment mMapFragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mMapFragment = (MapFragment) getFragmentManager()
                .findFragmentById(R.id.map_fragment);
        mMapFragment.getMapAsync(this);
    }

    @Override
    public void onMapReady(GoogleMap googleMap) {
        mGoogleMap = googleMap;

        List<List<LatLng>> holes = new ArrayList<>();

        // "hole" for Hyde Park
        List<LatLng> hole = new ArrayList<>();
        hole.add(new LatLng(51.509869, -0.191208));
        hole.add(new LatLng(51.513287, -0.158464));
        hole.add(new LatLng(51.505540, -0.151769));
        hole.add(new LatLng(51.502178, -0.174471));
        hole.add(new LatLng(51.502444, -0.187989));
        holes.add(hole);

        // "hole" for Regent's Park
        hole = new ArrayList<>();
        hole.add(new LatLng(51.530226, -0.167685));
        hole.add(new LatLng(51.534924, -0.163737));
        hole.add(new LatLng(51.537566, -0.151849));
        hole.add(new LatLng(51.535964, -0.146914));
        hole.add(new LatLng(51.525325, -0.145625));
        hole.add(new LatLng(51.523589, -0.155538));
        holes.add(hole);

        mGoogleMap.addPolygon(createPolygonWithHoles(holes));

        mGoogleMap.animateCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(51.519454, -0.168869), 14));
    }

    private static List<LatLng> createBoundsOfEntireMap() {
        final float delta = 0.01f;

        return new ArrayList<LatLng>() {{
            add(new LatLng(90 - delta, -180 + delta));
            add(new LatLng(0, -180 + delta));
            add(new LatLng(-90 + delta, -180 + delta));
            add(new LatLng(-90 + delta, 0));
            add(new LatLng(-90 + delta, 180 - delta));
            add(new LatLng(0, 180 - delta));
            add(new LatLng(90 - delta, 180 - delta));
            add(new LatLng(90 - delta, 0));
            add(new LatLng(90 - delta, -180 + delta));
        }};
    }

    static PolygonOptions createPolygonWithHoles(List<List<LatLng>> holes) {
        PolygonOptions polyOptions = new PolygonOptions()
                .fillColor(0x33000000)
                .addAll(createBoundsOfEntireMap())
                .strokeColor(0xFF000000)
                .strokeWidth(5);

        for (List<LatLng> hole : holes) {
            polyOptions.addHole(hole);
        }

        return polyOptions;
    }

}

and you get something like that:

Also you need bitmap circles as markers for polygon vertexes or draw it as Circle objects.

Update

For "hole-in-hole" case and "night-and-day" you should change .fillColor(0x33000000) to more dark, e.g. .fillColor(0xDD000000) and just add polygon with hole over "first" polygon. Something like this:

@Override
public void onMapReady(GoogleMap googleMap) {
    mGoogleMap = googleMap;

    List<List<LatLng>> holes = new ArrayList<>();

    // "hole" for Hyde Park
    List<LatLng> hole = new ArrayList<>();
    hole.add(new LatLng(51.509869, -0.191208));
    hole.add(new LatLng(51.513287, -0.158464));
    hole.add(new LatLng(51.505540, -0.151769));
    hole.add(new LatLng(51.502178, -0.174471));
    hole.add(new LatLng(51.502444, -0.187989));
    holes.add(hole);

    // "hole" for Regent's Park
    hole = new ArrayList<>();
    hole.add(new LatLng(51.530226, -0.167685));
    hole.add(new LatLng(51.534924, -0.163737));
    hole.add(new LatLng(51.537566, -0.151849));
    hole.add(new LatLng(51.535964, -0.146914));
    hole.add(new LatLng(51.525325, -0.145625));
    hole.add(new LatLng(51.523589, -0.155538));
    holes.add(hole);

    mGoogleMap.addPolygon(createPolygonWithHoles(holes));

    List<LatLng> holesInHolesPoly = new ArrayList<>();
    holesInHolesPoly.add(new LatLng(51.508184, -0.177805));
    holesInHolesPoly.add(new LatLng(51.509759, -0.164373));
    holesInHolesPoly.add(new LatLng(51.504549, -0.162399));
    holesInHolesPoly.add(new LatLng(51.503453, -0.177934));

    List<LatLng> holesInHolesHole = new ArrayList<>();
    holesInHolesHole.add(new LatLng(51.505883, -0.172999));
    holesInHolesHole.add(new LatLng(51.507992, -0.171025));
    holesInHolesHole.add(new LatLng(51.506308, -0.169738));

    hole = new ArrayList<>();
    hole.add(new LatLng(51.530226, -0.167685));

    PolygonOptions holeInHoles = new PolygonOptions()
            .fillColor(0xDD000000)
            .addAll(holesInHolesPoly)
            .addHole(holesInHolesHole)
            .strokeColor(0xFF000000)
            .strokeWidth(5);

    mGoogleMap.addPolygon(holeInHoles);

    mGoogleMap.animateCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(51.519454, -0.168869), 14));
}

and you are got something like that:

It's not a solution, but really good workaround. Or you can set "night" style for whole map and use custom TileProvider or GroundOverlay with "day" bitmap. Anyway - seems there are no "normal" way to create custom style for polygon part of the map.

来源：https://stackoverflow.com/questions/49778115/google-maps-api-different-map-style-for-polygon