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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.geotools</groupId>
<artifactId>gt-graph</artifactId>
<version>18.0</version>
</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) {
@Override
public 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;
}
@Override
public 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<Node> iterator = graph.getNodes().iterator();
List<Node> 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) {
@Override
public 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;
}
@Override
public 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GeodeticCalculator
GeodeticCalculator 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();
}
}原文作者：爱是与世界平行
原文链接：https://blog.51cto.com/lovebetterworld/5580637
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