废话不多说，直接上代码
MapPoint.java
public class MapPoint {
/**
* 经度
*/
private double lng;
/**
* 纬度
*/
private double lat;
public MapPoint() {
}
public MapPoint(double lng, double lat) {
this.lng = lng;
this.lat = lat;
}
@Override
public boolean equals(Object obj) {
if (obj instanceof MapPoint) {
MapPoint mapPoint = (MapPoint) obj;
return (mapPoint.getLng() == lng && mapPoint.getLat() == lat) ? true : false;
} else {
return false;
}
}
public double getLng() {
return lng;
}
public void setLng(double lng) {
this.lng = lng;
}
public double getLat() {
return lat;
}
public void setLat(double lat) {
this.lat = lat;
}
}GraphUtils.java
public class GraphUtils {
/**
* 判断点是否在多边形内(基本思路是用交点法)
*
* @param point
* @param boundaryPoints
* @return
*/
public static boolean isPointInPolygon(MapPoint point, MapPoint[] boundaryPoints) {
// 防止第一个点与最后一个点相同
if (boundaryPoints != null && boundaryPoints.length > 0
&& boundaryPoints[boundaryPoints.length - 1].equals(boundaryPoints[0])) {
boundaryPoints = Arrays.copyOf(boundaryPoints, boundaryPoints.length - 1);
}
int pointCount = boundaryPoints.length;
// 首先判断点是否在多边形的外包矩形内，如果在，则进一步判断，否则返回false
if (!isPointInRectangle(point, boundaryPoints)) {
return false;
}
// 如果点与多边形的其中一个顶点重合，那么直接返回true
for (int i = 0; i < pointCount; i++) {
if (point.equals(boundaryPoints[i])) {
return true;
}
}
/**
* 基本思想是利用X轴射线法，计算射线与多边形各边的交点，如果是偶数，则点在多边形外，否则在多边形内。还会考虑一些特殊情况，如点在多边形顶点上
* ， 点在多边形边上等特殊情况。
*/
// X轴射线与多边形的交点数
int intersectPointCount = 0;
// X轴射线与多边形的交点权值
float intersectPointWeights = 0;
// 浮点类型计算时候与0比较时候的容差
double precision = 2e-10;
// 边P1P2的两个端点
MapPoint point1 = boundaryPoints[0], point2;
// 循环判断所有的边
for (int i = 1; i <= pointCount; i++) {
point2 = boundaryPoints[i % pointCount];
/**
* 如果点的y坐标在边P1P2的y坐标开区间范围之外，那么不相交。
*/
if (point.getLat() < Math.min(point1.getLat(), point2.getLat())
|| point.getLat() > Math.max(point1.getLat(), point2.getLat())) {
point1 = point2;
continue;
}
/**
* 此处判断射线与边相交
*/
if (point.getLat() > Math.min(point1.getLat(), point2.getLat())
// 如果点的y坐标在边P1P2的y坐标开区间内
&& point.getLat() < Math.max(point1.getLat(), point2.getLat())) {
// 若边P1P2是垂直的
if (point1.getLng() == point2.getLng()) {
if (point.getLng() == point1.getLng()) {
// 若点在垂直的边P1P2上，则点在多边形内
return true;
} else if (point.getLng() < point1.getLng()) {
// 若点在在垂直的边P1P2左边，则点与该边必然有交点
++intersectPointCount;
}
} else {// 若边P1P2是斜线
// 点point的x坐标在点P1和P2的左侧
if (point.getLng() <= Math.min(point1.getLng(), point2.getLng())) {
++intersectPointCount;
}
// 点point的x坐标在点P1和P2的x坐标中间
else if (point.getLng() > Math.min(point1.getLng(), point2.getLng())
&& point.getLng() < Math.max(point1.getLng(), point2.getLng())) {
double slopeDiff = getSlopeDiff(point, point1, point2);
if (slopeDiff > 0) {
// 由于double精度在计算时会有损失，故匹配一定的容差。经试验，坐标经度可以达到0.0001
if (slopeDiff < precision) {
// 点在斜线P1P2上
return true;
} else {
// 点与斜线P1P2有交点
intersectPointCount++;
}
}
}
}
} else {
// 边P1P2水平
if (point1.getLat() == point2.getLat()) {
if (checkPointInLine(point, point1, point2)) {
return true;
}
}
/**
* 判断点通过多边形顶点
*/
if (((point.getLat() == point1.getLat() && point.getLng() < point1.getLng()))
|| (point.getLat() == point2.getLat() && point.getLng() < point2.getLng())) {
if (point2.getLat() < point1.getLat()) {
intersectPointWeights += -0.5;
} else if (point2.getLat() > point1.getLat()) {
intersectPointWeights += 0.5;
}
}
}
point1 = point2;
}
// 偶数在多边形外
if ((intersectPointCount + Math.abs(intersectPointWeights)) % 2 == 0) {
return false;
} else { // 奇数在多边形内
return true;
}
}
private static double getSlopeDiff(MapPoint point, MapPoint point1, MapPoint point2) {
double slopeDiff = 0.0d;
if (point1.getLat() > point2.getLat()) {
slopeDiff = (point.getLat() - point2.getLat()) / (point.getLng() - point2.getLng())
- (point1.getLat() - point2.getLat()) / (point1.getLng() - point2.getLng());
} else {
slopeDiff = (point.getLat() - point1.getLat()) / (point.getLng() - point1.getLng())
- (point2.getLat() - point1.getLat()) / (point2.getLng() - point1.getLng());
}
return slopeDiff;
}
private static boolean checkPointInLine(MapPoint point, MapPoint point1, MapPoint point2) {
if (point.getLng() <= Math.max(point1.getLng(), point2.getLng())
&& point.getLng() >= Math.min(point1.getLng(), point2.getLng())) {
// 若点在水平的边P1P2上，则点在多边形内
return true;
}
return false;
}
/**
* 判断点是否在矩形内在矩形边界上，也算在矩形内(根据这些点，构造一个外包矩形)
*
* @param point 点对象
* @param boundaryPoints 矩形边界点
* @return
*/
public static boolean isPointInRectangle(MapPoint point, MapPoint[] boundaryPoints) {
// 西南角点
MapPoint southWestPoint = getSouthWestPoint(boundaryPoints);
// 东北角点
MapPoint northEastPoint = getNorthEastPoint(boundaryPoints);
return (point.getLng() >= southWestPoint.getLng() && point.getLng() <= northEastPoint.getLng()
&& point.getLat() >= southWestPoint.getLat() && point.getLat() <= northEastPoint.getLat());
}
/**
* 根据这组坐标，画一个矩形，然后得到这个矩形西南角的顶点坐标
*
* @param vertexs
* @return
*/
private static MapPoint getSouthWestPoint(MapPoint[] vertexs) {
double minLng = vertexs[0].getLng(), minLat = vertexs[0].getLat();
for (MapPoint bmapPoint : vertexs) {
double lng = bmapPoint.getLng();
double lat = bmapPoint.getLat();
if (lng < minLng) {
minLng = lng;
}
if (lat < minLat) {
minLat = lat;
}
}
return new MapPoint(minLng, minLat);
}
/**
* 根据这组坐标，画一个矩形，然后得到这个矩形东北角的顶点坐标
*
* @param vertexs
* @return
*/
private static MapPoint getNorthEastPoint(MapPoint[] vertexs) {
double maxLng = 0.0d, maxLat = 0.0d;
for (MapPoint bmapPoint : vertexs) {
double lng = bmapPoint.getLng();
double lat = bmapPoint.getLat();
if (lng > maxLng) {
maxLng = lng;
}
if (lat > maxLat) {
maxLat = lat;
}
}
return new MapPoint(maxLng, maxLat);
}
}使用方式
GraphUtils.isPointInPolygon(MapPoint point,List<MapPoint> boundaryPoints)返回值是true，说明在区域内，否则不在
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