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MapLibre Android Java Utilities
package org.maplibre.geojson;
import androidx.annotation.Keep;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.TypeAdapter;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonWriter;
import org.maplibre.geojson.gson.GeoJsonAdapterFactory;
import org.maplibre.geojson.shifter.CoordinateShifterManager;
import java.io.IOException;
import java.util.List;
/**
* A point represents a single geographic position and is one of the seven Geometries found in the
* GeoJson spec.
*
* This adheres to the RFC 7946 internet standard when serialized into JSON. When deserialized, this
* class becomes an immutable object which should be initiated using its static factory methods.
*
* Coordinates are in x, y order (easting, northing for projected coordinates), longitude, and
* latitude for geographic coordinates), precisely in that order and using double values. Altitude
* or elevation MAY be included as an optional third parameter while creating this object.
*
* The size of a GeoJson text in bytes is a major interoperability consideration, and precision of
* coordinate values has a large impact on the size of texts when serialized. For geographic
* coordinates with units of degrees, 6 decimal places (a default common in, e.g., sprintf) amounts
* to about 10 centimeters, a precision well within that of current GPS systems. Implementations
* should consider the cost of using a greater precision than necessary.
*
* Furthermore, pertaining to altitude, the WGS 84 datum is a relatively coarse approximation of the
* geoid, with the height varying by up to 5 m (but generally between 2 and 3 meters) higher or
* lower relative to a surface parallel to Earth's mean sea level.
*
* A sample GeoJson Point's provided below (in its serialized state).
*
* {
* "type": "Point",
* "coordinates": [100.0, 0.0]
* }
*
*
* @since 1.0.0
*/
@Keep
public final class Point implements CoordinateContainer> {
private static final String TYPE = "Point";
@NonNull
private final String type;
@Nullable
private final BoundingBox bbox;
@NonNull
private final List coordinates;
/**
* Create a new instance of this class by passing in a formatted valid JSON String. If you are
* creating a Point object from scratch it is better to use one of the other provided static
* factory methods such as {@link #fromLngLat(double, double)}. While no limit is placed
* on decimal precision, for performance reasons when serializing and deserializing it is
* suggested to limit decimal precision to within 6 decimal places.
*
* @param json a formatted valid JSON string defining a GeoJson Point
* @return a new instance of this class defined by the values passed inside this static factory
* method
* @since 1.0.0
*/
public static Point fromJson(@NonNull String json) {
GsonBuilder gson = new GsonBuilder();
gson.registerTypeAdapterFactory(GeoJsonAdapterFactory.create());
return gson.create().fromJson(json, Point.class);
}
/**
* Create a new instance of this class defining a longitude and latitude value in that respective
* order. While no limit is placed on decimal precision, for performance reasons
* when serializing and deserializing it is suggested to limit decimal precision to within 6
* decimal places.
*
* @param longitude a double value representing the x position of this point
* @param latitude a double value representing the y position of this point
* @return a new instance of this class defined by the values passed inside this static factory
* method
* @since 3.0.0
*/
public static Point fromLngLat(double longitude, double latitude) {
List coordinates =
CoordinateShifterManager.getCoordinateShifter().shiftLonLat(longitude, latitude);
return new Point(TYPE, null, coordinates);
}
/**
* Create a new instance of this class defining a longitude and latitude value in that respective
* order. While no limit is placed on decimal precision, for performance reasons
* when serializing and deserializing it is suggested to limit decimal precision to within 6
* decimal places. An optional altitude value can be passed in and can vary between negative
* infinity and positive infinity.
*
* @param longitude a double value representing the x position of this point
* @param latitude a double value representing the y position of this point
* @param bbox optionally include a bbox definition as a double array
* @return a new instance of this class defined by the values passed inside this static factory
* method
* @since 3.0.0
*/
public static Point fromLngLat(double longitude, double latitude,
@Nullable BoundingBox bbox) {
List coordinates =
CoordinateShifterManager.getCoordinateShifter().shiftLonLat(longitude, latitude);
return new Point(TYPE, bbox, coordinates);
}
/**
* Create a new instance of this class defining a longitude and latitude value in that respective
* order. While no limit is placed on decimal precision, for performance reasons
* when serializing and deserializing it is suggested to limit decimal precision to within 6
* decimal places. An optional altitude value can be passed in and can vary between negative
* infinity and positive infinity.
*
* @param longitude a double value representing the x position of this point
* @param latitude a double value representing the y position of this point
* @param altitude a double value which can be negative or positive infinity representing either
* elevation or altitude
* @return a new instance of this class defined by the values passed inside this static factory
* method
* @since 3.0.0
*/
public static Point fromLngLat(double longitude, double latitude, double altitude) {
List coordinates =
CoordinateShifterManager.getCoordinateShifter().shiftLonLatAlt(longitude, latitude, altitude);
return new Point(TYPE, null, coordinates);
}
/**
* Create a new instance of this class defining a longitude and latitude value in that respective
* order. While no limit is placed on decimal precision, for performance reasons
* when serializing and deserializing it is suggested to limit decimal precision to within 6
* decimal places. An optional altitude value can be passed in and can vary between negative
* infinity and positive infinity.
*
* @param longitude a double value representing the x position of this point
* @param latitude a double value representing the y position of this point
* @param altitude a double value which can be negative or positive infinity representing either
* elevation or altitude
* @param bbox optionally include a bbox definition as a double array
* @return a new instance of this class defined by the values passed inside this static factory
* method
* @since 3.0.0
*/
public static Point fromLngLat(double longitude, double latitude,
double altitude, @Nullable BoundingBox bbox) {
List coordinates =
CoordinateShifterManager.getCoordinateShifter().shiftLonLatAlt(longitude, latitude, altitude);
return new Point(TYPE, bbox, coordinates);
}
static Point fromLngLat(@NonNull double[] coords) {
if (coords.length == 2) {
return Point.fromLngLat(coords[0], coords[1]);
} else if (coords.length > 2) {
return Point.fromLngLat(coords[0], coords[1], coords[2]);
}
return null;
}
Point(String type, @Nullable BoundingBox bbox, List coordinates) {
if (type == null) {
throw new NullPointerException("Null type");
}
this.type = type;
this.bbox = bbox;
if (coordinates == null || coordinates.size() == 0) {
throw new NullPointerException("Null coordinates");
}
this.coordinates = coordinates;
}
/**
* This returns a double value representing the x or easting position of
* this point. ideally, this value would be restricted to 6 decimal places to correctly follow the
* GeoJson spec.
*
* @return a double value representing the x or easting position of this
* point
* @since 3.0.0
*/
public double longitude() {
return coordinates().get(0);
}
/**
* This returns a double value representing the y or northing position of
* this point. ideally, this value would be restricted to 6 decimal places to correctly follow the
* GeoJson spec.
*
* @return a double value representing the y or northing position of this
* point
* @since 3.0.0
*/
public double latitude() {
return coordinates().get(1);
}
/**
* Optionally, the coordinate spec in GeoJson allows for altitude values to be placed inside the
* coordinate array. {@link #hasAltitude()} can be used to determine if this value was set during
* initialization of this Point instance. This double value should only be used to represent
* either the elevation or altitude value at this particular point.
*
* @return a double value ranging from negative to positive infinity
* @since 3.0.0
*/
public double altitude() {
if (coordinates().size() < 3) {
return Double.NaN;
}
return coordinates().get(2);
}
/**
* Optionally, the coordinate spec in GeoJson allows for altitude values to be placed inside the
* coordinate array. If an altitude value was provided while initializing this instance, this will
* return true.
*
* @return true if this instance of point contains an altitude value
* @since 3.0.0
*/
public boolean hasAltitude() {
return !Double.isNaN(altitude());
}
/**
* This describes the TYPE of GeoJson geometry this object is, thus this will always return
* {@link Point}.
*
* @return a String which describes the TYPE of geometry, for this object it will always return
* {@code Point}
* @since 1.0.0
*/
@NonNull
@Override
public String type() {
return type;
}
/**
* A Feature Collection might have a member named {@code bbox} to include information on the
* coordinate range for it's {@link Feature}s. The value of the bbox member MUST be a list of
* size 2*n where n is the number of dimensions represented in the contained feature geometries,
* with all axes of the most southwesterly point followed by all axes of the more northeasterly
* point. The axes order of a bbox follows the axes order of geometries.
*
* @return a list of double coordinate values describing a bounding box
* @since 3.0.0
*/
@Nullable
@Override
public BoundingBox bbox() {
return bbox;
}
/**
* Provide a single double array containing the longitude, latitude, and optionally an
* altitude/elevation. {@link #longitude()}, {@link #latitude()}, and {@link #altitude()} are all
* avaliable which make getting specific coordinates more direct.
*
* @return a double array which holds this points coordinates
* @since 3.0.0
*/
@NonNull
@Override
public List coordinates() {
return coordinates;
}
/**
* This takes the currently defined values found inside this instance and converts it to a GeoJson
* string.
*
* @return a JSON string which represents this Point geometry
* @since 1.0.0
*/
@Override
public String toJson() {
GsonBuilder gson = new GsonBuilder();
gson.registerTypeAdapterFactory(GeoJsonAdapterFactory.create());
return gson.create().toJson(this);
}
/**
* Gson TYPE adapter for parsing Gson to this class.
*
* @param gson the built {@link Gson} object
* @return the TYPE adapter for this class
* @since 3.0.0
*/
public static TypeAdapter typeAdapter(Gson gson) {
return new Point.GsonTypeAdapter(gson);
}
@Override
public String toString() {
return "Point{"
+ "type=" + type + ", "
+ "bbox=" + bbox + ", "
+ "coordinates=" + coordinates
+ "}";
}
@Override
public boolean equals(Object obj) {
if (obj == this) {
return true;
}
if (obj instanceof Point) {
Point that = (Point) obj;
return (this.type.equals(that.type()))
&& ((this.bbox == null) ? (that.bbox() == null) : this.bbox.equals(that.bbox()))
&& (this.coordinates.equals(that.coordinates()));
}
return false;
}
@Override
public int hashCode() {
int hashCode = 1;
hashCode *= 1000003;
hashCode ^= type.hashCode();
hashCode *= 1000003;
hashCode ^= (bbox == null) ? 0 : bbox.hashCode();
hashCode *= 1000003;
hashCode ^= coordinates.hashCode();
return hashCode;
}
/**
* TypeAdapter for Point geometry.
*
* @since 4.6.0
*/
static final class GsonTypeAdapter extends BaseGeometryTypeAdapter> {
GsonTypeAdapter(Gson gson) {
super(gson, new ListOfDoublesCoordinatesTypeAdapter());
}
@Override
@SuppressWarnings("unchecked")
public void write(JsonWriter jsonWriter, Point object) throws IOException {
writeCoordinateContainer(jsonWriter, object);
}
@Override
@SuppressWarnings("unchecked")
public Point read(JsonReader jsonReader) throws IOException {
return (Point)readCoordinateContainer(jsonReader);
}
@Override
CoordinateContainer> createCoordinateContainer(String type,
BoundingBox bbox,
List coordinates) {
return new Point(type == null ? "Point" : type, bbox, coordinates);
}
}
}
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