我正在用 Android Studio 编写一个 Android 应用程序（使用 Java）。该应用程序使用谷歌地图，并有一个图层，其中包含从地理服务器获取的字段所有权信息。设置它的代码如下，并且运行良好。
public class App1Step1 extends FragmentActivity implements OnMapReadyCallback {
private GoogleMap mMap;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_app1_step1);
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
}
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
mMap.setMapType(GoogleMap.MAP_TYPE_SATELLITE);
TileProvider tileProvider = TileProviderFactory.getTileProvider();
mMap.addTileOverlay(new TileOverlayOptions().tileProvider(tileProvider));
}
}
class TileProviderFactory {
private static final String GEOSERVER_FORMAT =
"http://xxxxxxxx.at/geoserver/wms" +
"?service=WMS" +
"&version=1.1.1" +
"&request=GetMap" +
"&layers=satgrass:INSPIRE_SCHLAEGE_2020_POLYGON" +
"&bbox=%f,%f,%f,%f" +
"&width=256" +
"&height=256" +
"&srs=EPSG:900913" +
"&format=image/png" +
"&transparent=true";
static TileProvider getTileProvider() {
TileProvider tileProvider = new WMSTileProvider(256,256) {
@Override
public synchronized URL getTileUrl(int x, int y, int zoom) {
double[] bbox = getBoundingBox(x, y, zoom);
String s = String.format(Locale.US, GEOSERVER_FORMAT, bbox[MINX], bbox[MINY], bbox[MAXX], bbox[MAXY]);
URL url = null;
try {
url = new URL(s);
} catch (MalformedURLException e) {
throw new AssertionError(e);
}
return url;
}
};
return tileProvider;
}
}
abstract class WMSTileProvider extends UrlTileProvider {
// Web Mercator n/w corner of the map.
private static final double[] TILE_ORIGIN = {-20037508.34789244, 20037508.34789244};
//array indexes for that data
private static final int ORIG_X = 0;
private static final int ORIG_Y = 1; // "
// Size of square world map in meters, using WebMerc projection.
private static final double MAP_SIZE = 20037508.34789244 * 2;
// array indexes for array to hold bounding boxes.
protected static final int MINX = 0;
protected static final int MAXX = 1;
protected static final int MINY = 2;
protected static final int MAXY = 3;
// Construct with tile size in pixels, normally 256, see parent class.
public WMSTileProvider(int x, int y) {
super(x, y);
}
// Return a web Mercator bounding box given tile x/y indexes and a zoom
// level.
protected double[] getBoundingBox(int x, int y, int zoom) {
double tileSize = MAP_SIZE / Math.pow(2, zoom);
double minx = TILE_ORIGIN[ORIG_X] + x * tileSize;
double maxx = TILE_ORIGIN[ORIG_X] + (x+1) * tileSize;
double miny = TILE_ORIGIN[ORIG_Y] - (y+1) * tileSize;
double maxy = TILE_ORIGIN[ORIG_Y] - y * tileSize;
double[] bbox = new double[4];
bbox[MINX] = minx;
bbox[MINY] = miny;
bbox[MAXX] = maxx;
bbox[MAXY] = maxy;
return bbox;
}
}
上面的代码将在 Google 地图上生成以下叠加层。在地理服务器上，图层保存为 EPSG:31287 (Austria Lambert)。
我现在想做的是在单击其中一个字段时获取功能信息。我尝试了很多，但无法弄清楚如何计算必要的值（宽度、高度、x、y、bbox）以从我点击的纬度和经度中获取特征信息。具体来说，这些是我缺少的查询中的值。
String url = "http://xxxxxxxxxxx.at/geoserver/wms" +
"?service=WMS" +
"&version=1.1.1" +
"&request=GetFeatureInfo" +
"&layers=satgrass:INSPIRE_SCHLAEGE_2020_POLYGON" +
"&query_layers=satgrass:INSPIRE_SCHLAEGE_2020_POLYGON" +
"&exceptions=application/vnd.ogc.se_inimage" +
"&x=" + // ????????
"&y=" + // ????????
"&bbox=" + // ????????
"&width=" + // ????????
"&height=" + // ????????
"&srs=EPSG:900913" + // EPSG:900913 or EPSG:31287 ?
"&format=image/png" +
"&info_format=application/json" +
"&transparent=true" +
"&feature_count=50";
到目前为止我所做的（我认为）是计算我从纬度、经度和缩放级别单击的位置的 x 和 y 位置。
private void getFeatureInfo(LatLng latLng) {
// get current zoom
int zoom = (int)mMap.getCameraPosition().zoom;
// get "click" point coordinates in pixels
long pointNorthWestX = lonToX(latLng.longitude, zoom);
long pointNorthWestY = latToY(latLng.latitude, zoom);
}
public static long lonToX(double lon, int zoom) {
int offset = 256 << (zoom - 1);
return (int)Math.floor(offset + (offset * lon / 180));
}
public static long latToY(double lat, int zoom) {
int offset = 256 << (zoom - 1);
return (int)Math.floor(offset - offset / Math.PI * Math.log((1 + Math.sin(Math.toRadians(lat))) / (1 - Math.sin(Math.toRadians(lat)))) / 2);
}
不幸的是，与我在 geoserver 上的图层预览中单击相同位置时得到的值相比，这些值似乎相差甚远。
有谁知道从纬度、经度和缩放级别获取我单击的位置的特征信息所需的计算步骤是什么？我将非常感谢您对此的任何帮助。