GeoTools的AStar算法实现，自定义Node及Edge

1 核心依赖包

开发语言java

<dependency>   <groupId>org.geotoolsgroupId>    <artifactId>gt-graphartifactId>   <version>18.0version>
dependency>

Geotools提供了一个Graph的扩展包，这个扩展包不只是对A*算法进行了实现，也对算法Dijkstra进行了实现，两种算法在Geotools中的用法基本一致。

2 基本概念介绍

2.1 Graph（图）

可以理解为是一个将要建模的对象的容器，图里面存放的是很多的点（node）和边（edge）。

2.2 Node（点）

Node（点）是将要建模的对象，它可以指的是实际地图中的一个坐标点，也可以指的是任意坐标系中的一个点，也可以指的是拓扑图里面的一个节点。构建好的Node全部都存放在Graph中。

2.3 Edge（边）

边是指两个Node（点）的关联，一个边下面会有两个点，在图中的边是认为两个点之间可到达，边下面两个点分别表示NodeA和NodeB，节点方向为NodeA->NodeB,

3 在地图上标注POI点，并采集每个点的坐标

如图，合肥紫云山公园（随便选的公园），随意标注13个POI点（随便标注的点），采集这13个点的坐标。

坐标采集可以通过百度、或者高德的坐标采集器实现。

如高德坐标采集器地址：高德地图获取地图坐标（GCJ-02坐标） - openGPS.cn

定位到该公园：117.329088,31.739236

获取到13个点的坐标。

4 标注出13个POI的拓扑关系，即到达关系

如图，标注出每个POI的拓扑关系（随便标注的）

5 生成Node节点以及Edge边，并标注POI点与Node节点对应关系

Node生成出来是无序的，如图所示（需根据生成的Node节点和POI点进行对应）。

//构造点
BasicGraphGenerator basicGraphGenerator = new BasicGraphGenerator();
BasicGraphBuilder basicGraphBuilder = new BasicGraphBuilder();
Coordinate[] coordinates = new Coordinate[12];
coordinates[0] = new Coordinate(104.069649, 30.542246);
coordinates[1] = new Coordinate(104.071001, 30.542283);
coordinates[2] = new Coordinate(104.073458, 30.542329);
.....................
List<Node> nodeList = new ArrayList<>();
for (int i = 0; i < 12; i++) {Node node = basicGraphGenerator.getGraphBuilder().buildNode();basicGraphGenerator.getGraphBuilder().addNode(node);node.setObject(coordinates[i]);node.setID(i);node.setCount(i);node.setVisited(true);basicGraphBuilder.addNode(node);nodeList.add(node);
}

Node生成示例数据如下：V=[6, 9, 1, 7, 4, 2, 8, 10, 5, 11, 3, 0]

Edge生成：

public static Graph buildEdge(BasicGraphBuilder basicGraphBuilder, List<Node> nodeList) {BasicGraphGenerator basicGraphGenerator = new BasicGraphGenerator();Map<Integer, String> map = new HashMap<>();//维护Edge关系map.put(1, "2");map.put(2, "3,12");map.put(3, "4,10");map.put(4, "5");map.put(5, "6");map.put(6, "7,11");map.put(7, "8");map.put(8, "1");map.put(9, "4");map.put(10, "9,11");map.put(11, "12,7");map.put(12, "7");for (Map.Entry<Integer, String> entry : map.entrySet()) {if (entry.getValue().split(",").length > 1) {String[] strings = entry.getValue().split(",");for (String string : strings) {//判断nodeList数组越界情况if (Integer.parseInt(string) == 12) {string = "11";}Edge edge = new BasicEdge(nodeList.get(entry.getKey()), nodeList.get(Integer.parseInt(string)));Long distance = getDistance(nodeList.get(entry.getKey()), nodeList.get(Integer.parseInt(string)));edge.setObject(distance);edge.setVisited(true);basicGraphBuilder.addEdge(edge);}} else {Integer key = entry.getKey();//判断nodeList数组越界情况if (Integer.parseInt(entry.getValue()) == 12) {entry.setValue("11");}//判断nodeList数组越界情况if (key == 12) {key = 11;}//构造边Edge edge = new BasicEdge(nodeList.get(key), nodeList.get(Integer.parseInt(entry.getValue())));Long distance = getDistance(nodeList.get(key), nodeList.get(Integer.parseInt(entry.getValue())));edge.setObject(distance);edge.setVisited(true);basicGraphBuilder.addEdge(edge);}}System.out.println(basicGraphBuilder.getNodes());System.out.println(basicGraphBuilder.getGraph());return basicGraphBuilder.getGraph();
}

Edge生成示例数据如下：

E=[13 (2,3), 25 (10,11), 14 (2,11), 16 (3,10), 18 (5,6), 17 (4,5), 15 (3,4), 24 (10,9), 22 (8,1), 19 (6,7), 23 (9,4), 21 (7,8), 28 (11,7), 20 (6,11), 26 (11,11), 12 (1,2), 27 (11,7)]

注意，Edge括号中，描述的为POI点的序号。

标注Edge的关系，示例如图。

6 使用AStar导航进行计算路径

public static void AStarShortestPath(Graph graph, Node startNode, Node endNode) {AStarIterator.AStarFunctions aStarFunction = new AStarIterator.AStarFunctions(endNode) {@Overridepublic double cost(AStarIterator.AStarNode aStarNode, AStarIterator.AStarNode aStarNode1) {Edge edge = aStarNode.getNode().getEdge(aStarNode1.getNode());System.out.println("edge=" + edge.getID() + ",Distance" + edge.getObject());/*SimpleFeature feature = (SimpleFeature) edge.getObject();Geometry geometry = (Geometry) feature.getDefaultGeometry();System.out.println(aStarNode.getH());return geometry.getLength();*/
//                return Integer.parseInt(String.valueOf(edge.getObject()));return 10;}@Overridepublic double h(Node node) {return -10;}};Date start = new Date();AStarShortestPathFinder aStarPf = new AStarShortestPathFinder(graph, startNode, endNode, aStarFunction);try {aStarPf.calculate();Date end = new Date();System.out.println("AStar算法耗时：" + (end.getTime() - start.getTime()));aStarPf.getPath();System.out.println("AStar算法距离：" + getPathLength(aStarPf.getPath()));
/*            Iterator it = aStarPf.getPath().iterator();String result = "";while (it.hasNext()) {Node node = (Node) it.next();result = result + node.getObject().toString();}System.out.println("result:" + result);*/} catch (Exception e) {e.printStackTrace();}}

7 完整代码

import org.geotools.data.DataStore;
import org.geotools.data.shapefile.ShapefileDataStore;
import org.geotools.data.simple.SimpleFeatureCollection;
import org.geotools.feature.FeatureIterator;
import org.geotools.graph.build.basic.BasicGraphBuilder;
import org.geotools.graph.build.basic.BasicGraphGenerator;
import org.geotools.graph.build.feature.FeatureGraphGenerator;
import org.geotools.graph.build.line.LineStringGraphGenerator;
import org.geotools.graph.path.AStarShortestPathFinder;
import org.geotools.graph.path.Path;
import org.geotools.graph.structure.Edge;
import org.geotools.graph.structure.Graph;
import org.geotools.graph.structure.Node;
import org.geotools.graph.structure.basic.BasicEdge;
import org.geotools.graph.traverse.standard.AStarIterator;
import org.geotools.referencing.GeodeticCalculator;
import org.geotools.referencing.crs.DefaultGeographicCRS;
import org.locationtech.jts.geom.Coordinate;
import org.opengis.feature.Feature;import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.util.*;public class NavigationUtil {/*public static void main(String[] args) throws IOException {File file = new File("E:\\公交路线.shp");//1.读取shp数据DataStore dataStore = readShapeFile(file);SimpleFeatureSource featureSource = dataStore.getFeatureSource(dataStore.getTypeNames()[0]);SimpleFeatureCollection simFeatureCollect = featureSource.getFeatures();System.out.println("shp文件原始线的个数：" + simFeatureCollect.size());//2.创建graph数据结构Graph graph = buildGraph(simFeatureCollect);Iterator iterator = graph.getNodes().iterator();List nodeArrayList = new ArrayList<>();while (iterator.hasNext()) {nodeArrayList.add(iterator.next());}System.out.println("节点：" + graph.getNodes());System.out.println("边：" + graph.getEdges());System.out.println(nodeArrayList.get(74));System.out.println(nodeArrayList.get(283));AStarShortestPath(graph, nodeArrayList.get(74), nodeArrayList.get(283));}*/public static void main(String[] args) throws IOException {buildNodeAndEdgeGraph();}public static void AStarShortestPath(Graph graph, Node startNode, Node endNode) {AStarIterator.AStarFunctions aStarFunction = new AStarIterator.AStarFunctions(endNode) {@Overridepublic double cost(AStarIterator.AStarNode aStarNode, AStarIterator.AStarNode aStarNode1) {Edge edge = aStarNode.getNode().getEdge(aStarNode1.getNode());System.out.println("edge=" + edge.getID() + ",Distance" + edge.getObject());/*SimpleFeature feature = (SimpleFeature) edge.getObject();Geometry geometry = (Geometry) feature.getDefaultGeometry();System.out.println(aStarNode.getH());return geometry.getLength();*/
//                return Integer.parseInt(String.valueOf(edge.getObject()));return 10;}@Overridepublic double h(Node node) {return -10;}};Date start = new Date();AStarShortestPathFinder aStarPf = new AStarShortestPathFinder(graph, startNode, endNode, aStarFunction);try {aStarPf.calculate();Date end = new Date();System.out.println("AStar算法耗时：" + (end.getTime() - start.getTime()));aStarPf.getPath();System.out.println("AStar算法距离：" + getPathLength(aStarPf.getPath()));
/*            Iterator it = aStarPf.getPath().iterator();String result = "";while (it.hasNext()) {Node node = (Node) it.next();result = result + node.getObject().toString();}System.out.println("result:" + result);*/} catch (Exception e) {e.printStackTrace();}}public static DataStore readShapeFile(File shpFile) throws MalformedURLException {ShapefileDataStore shapefileDataStore = new ShapefileDataStore(shpFile.toURI().toURL());return shapefileDataStore;}public static Graph buildNodeAndEdgeGraph() {//构造点BasicGraphGenerator basicGraphGenerator = new BasicGraphGenerator();BasicGraphBuilder basicGraphBuilder = new BasicGraphBuilder();Coordinate[] coordinates = new Coordinate[12];coordinates[0] = new Coordinate(104.069649, 30.542246);coordinates[1] = new Coordinate(104.071001, 30.542283);//此处省略好多点，麻烦自己手动采集List<Node> nodeList = new ArrayList<>();for (int i = 0; i < 12; i++) {Node node = basicGraphGenerator.getGraphBuilder().buildNode();basicGraphGenerator.getGraphBuilder().addNode(node);node.setObject(coordinates[i]);node.setID(i);node.setCount(i);node.setVisited(true);basicGraphBuilder.addNode(node);nodeList.add(node);}buildEdge(basicGraphBuilder, nodeList);System.out.println("nodeList:" + nodeList);AStarShortestPath(basicGraphBuilder.getGraph(), nodeList.get(1), nodeList.get(5));return basicGraphBuilder.getGraph();}public static Graph buildGraph(SimpleFeatureCollection simFeatureCollect) {//构造线LineStringGraphGenerator lineStringGen = new LineStringGraphGenerator();FeatureGraphGenerator featureGen = new FeatureGraphGenerator(lineStringGen);FeatureIterator iter = simFeatureCollect.features();while (iter.hasNext()) {Feature next = iter.next();featureGen.add(next);}iter.close();return featureGen.getGraph();}public static Graph buildEdge(BasicGraphBuilder basicGraphBuilder, List<Node> nodeList) {BasicGraphGenerator basicGraphGenerator = new BasicGraphGenerator();Map<Integer, String> map = new HashMap<>();map.put(1, "2");map.put(2, "3,12");map.put(3, "4,10");map.put(4, "5");map.put(5, "6");map.put(6, "7,11");map.put(7, "8");map.put(8, "1");map.put(9, "4");map.put(10, "9,11");map.put(11, "12,7");map.put(12, "7");for (Map.Entry<Integer, String> entry : map.entrySet()) {if (entry.getValue().split(",").length > 1) {String[] strings = entry.getValue().split(",");for (String string : strings) {if (Integer.parseInt(string) == 12) {string = "11";}Edge edge = new BasicEdge(nodeList.get(entry.getKey()), nodeList.get(Integer.parseInt(string)));Long distance = getDistance(nodeList.get(entry.getKey()), nodeList.get(Integer.parseInt(string)));edge.setObject(distance);edge.setVisited(true);basicGraphBuilder.addEdge(edge);}} else {Integer key = entry.getKey();if (Integer.parseInt(entry.getValue()) == 12) {entry.setValue("11");}if (key == 12) {key = 11;}//构造边Edge edge = new BasicEdge(nodeList.get(key), nodeList.get(Integer.parseInt(entry.getValue())));Long distance = getDistance(nodeList.get(key), nodeList.get(Integer.parseInt(entry.getValue())));edge.setObject(distance);edge.setVisited(true);basicGraphBuilder.addEdge(edge);}}System.out.println(basicGraphBuilder.getNodes());System.out.println(basicGraphBuilder.getGraph());return basicGraphBuilder.getGraph();}public static String getPathLength(Path path) {return path.toString();}//计算两个节点的经纬度距离public static Long getDistance(Node nodeA, Node nodeB) {// 84坐标系构造GeodeticCalculatorGeodeticCalculator geodeticCalculator = new GeodeticCalculator(DefaultGeographicCRS.WGS84);Coordinate coordinate1 = (Coordinate) nodeA.getObject();Coordinate coordinate2 = (Coordinate) nodeB.getObject();// 起点经纬度geodeticCalculator.setStartingGeographicPoint(coordinate1.getX(), coordinate1.getY());// 末点经纬度geodeticCalculator.setDestinationGeographicPoint(coordinate2.getX(), coordinate2.getY());// 计算距离，单位：米double orthodromicDistance = geodeticCalculator.getOrthodromicDistance();return new Double(orthodromicDistance).longValue();}
}

8 参考文章

• geoTools的A*（A star）算法计算最优路径 - 掘金 (juejin.cn)

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