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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.utils.PolylineUtils;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
/**
* A linestring represents two or more geographic points that share a relationship 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.
*
* The list of points must be equal to or greater than 2. A LineString has non-zero length and
* zero area. It may approximate a curve and need not be straight. Unlike a LinearRing, a LineString
* is not closed.
*
* When representing a LineString that crosses the antimeridian, interoperability is improved by
* modifying their geometry. Any geometry that crosses the antimeridian SHOULD be represented by
* cutting it in two such that neither part's representation crosses the antimeridian.
*
* For example, a line extending from 45 degrees N, 170 degrees E across the antimeridian to 45
* degrees N, 170 degrees W should be cut in two and represented as a MultiLineString.
*
* A sample GeoJson LineString's provided below (in it's serialized state).
*
* {
* "TYPE": "LineString",
* "coordinates": [
* [100.0, 0.0],
* [101.0, 1.0]
* ]
* }
*
* Look over the {@link Point} documentation to get more
* information about formatting your list of point objects correctly.
*
* @since 1.0.0
*/
@Keep
public final class LineString implements CoordinateContainer> {
private static final String TYPE = "LineString";
private final String type;
private final BoundingBox bbox;
private final List coordinates;
/**
* Create a new instance of this class by passing in a formatted valid JSON String. If you are
* creating a LineString object from scratch it is better to use one of the other provided static
* factory methods such as {@link #fromLngLats(List)}. For a valid lineString to exist, it must
* have at least 2 coordinate entries. The LineString should also have non-zero distance and zero
* area.
*
* @param json a formatted valid JSON string defining a GeoJson LineString
* @return a new instance of this class defined by the values passed inside this static factory
* method
* @since 1.0.0
*/
public static LineString fromJson(String json) {
GsonBuilder gson = new GsonBuilder();
gson.registerTypeAdapterFactory(GeoJsonAdapterFactory.create());
return gson.create().fromJson(json, LineString.class);
}
/**
* Create a new instance of this class by defining a {@link MultiPoint} object and passing. The
* multipoint object should comply with the GeoJson specifications described in the documentation.
*
* @param multiPoint which will make up the LineString geometry
* @return a new instance of this class defined by the values passed inside this static factory
* method
* @since 3.0.0
*/
public static LineString fromLngLats(@NonNull MultiPoint multiPoint) {
return new LineString(TYPE, null, multiPoint.coordinates());
}
/**
* Create a new instance of this class by defining a list of {@link Point}s which follow the
* correct specifications described in the Point documentation. Note that there should not be any
* duplicate points inside the list and the points combined should create a LineString with a
* distance greater than 0.
*
* Note that if less than 2 points are passed in, a runtime exception will occur.
*
*
* @param points a list of {@link Point}s which make up the LineString geometry
* @return a new instance of this class defined by the values passed inside this static factory
* method
* @since 3.0.0
*/
public static LineString fromLngLats(@NonNull List points) {
return new LineString(TYPE, null, points);
}
/**
* Create a new instance of this class by defining a list of {@link Point}s which follow the
* correct specifications described in the Point documentation. Note that there should not be any
* duplicate points inside the list and the points combined should create a LineString with a
* distance greater than 0.
*
* Note that if less than 2 points are passed in, a runtime exception will occur.
*
*
* @param points a list of {@link Point}s which make up the LineString geometry
* @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 LineString fromLngLats(@NonNull List points, @Nullable BoundingBox bbox) {
return new LineString(TYPE, bbox, points);
}
/**
* Create a new instance of this class by defining a {@link MultiPoint} object and passing. The
* multipoint object should comply with the GeoJson specifications described in the documentation.
*
* @param multiPoint which will make up the LineString geometry
* @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 LineString fromLngLats(@NonNull MultiPoint multiPoint, @Nullable BoundingBox bbox) {
return new LineString(TYPE, bbox, multiPoint.coordinates());
}
LineString(String type, @Nullable BoundingBox bbox, List coordinates) {
if (type == null) {
throw new NullPointerException("Null type");
}
this.type = type;
this.bbox = bbox;
if (coordinates == null) {
throw new NullPointerException("Null coordinates");
}
this.coordinates = coordinates;
}
static LineString fromLngLats(double[][] coordinates) {
ArrayList converted = new ArrayList<>(coordinates.length);
for (double[] coordinate : coordinates) {
converted.add(Point.fromLngLat(coordinate));
}
return LineString.fromLngLats(converted);
}
/**
* Create a new instance of this class by convert a polyline string into a lineString. This is
* handy when an API provides you with an encoded string representing the line geometry and you'd
* like to convert it to a useful LineString object. Note that the precision that the string
* geometry was encoded with needs to be known and passed into this method using the precision
* parameter.
*
* @param polyline encoded string geometry to decode into a new LineString instance
* @param precision The encoded precision which must match the same precision used when the string
* was first encoded
* @return a new instance of this class defined by the values passed inside this static factory
* method
* @since 1.0.0
*/
public static LineString fromPolyline(@NonNull String polyline, int precision) {
return LineString.fromLngLats(PolylineUtils.decode(polyline, precision), null);
}
/**
* This describes the TYPE of GeoJson geometry this object is, thus this will always return
* {@link LineString}.
*
* @return a String which describes the TYPE of geometry, for this object it will always return
* {@code LineString}
* @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;
}
/**
* Provides the list of {@link Point}s that make up the LineString geometry.
*
* @return a list of points
* @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 LineString geometry
* @since 1.0.0
*/
@Override
public String toJson() {
GsonBuilder gson = new GsonBuilder();
gson.registerTypeAdapterFactory(GeoJsonAdapterFactory.create());
return gson.create().toJson(this);
}
/**
* Encode this LineString into a Polyline string for easier serializing. When passing geometry
* information over a mobile network connection, encoding the geometry first will generally result
* in less bandwidth usage.
*
* @param precision the encoded precision which fits your best use-case
* @return a string describing the geometry of this LineString
* @since 1.0.0
*/
public String toPolyline(int precision) {
return PolylineUtils.encode(coordinates(), precision);
}
/**
* 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 LineString.GsonTypeAdapter(gson);
}
@Override
public String toString() {
return "LineString{"
+ "type=" + type + ", "
+ "bbox=" + bbox + ", "
+ "coordinates=" + coordinates
+ "}";
}
@Override
public boolean equals(Object obj) {
if (obj == this) {
return true;
}
if (obj instanceof LineString) {
LineString that = (LineString) 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 LineString geometry.
*
* @since 4.6.0
*/
static final class GsonTypeAdapter extends BaseGeometryTypeAdapter> {
GsonTypeAdapter(Gson gson) {
super(gson, new ListOfPointCoordinatesTypeAdapter());
}
@Override
public void write(JsonWriter jsonWriter, LineString object) throws IOException {
writeCoordinateContainer(jsonWriter, object);
}
@Override
public LineString read(JsonReader jsonReader) throws IOException {
return (LineString) readCoordinateContainer(jsonReader);
}
@Override
CoordinateContainer> createCoordinateContainer(String type,
BoundingBox bbox,
List coordinates) {
return new LineString(type == null ? "LineString" : type, bbox, coordinates);
}
}
}
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