应项目需求，需要判断一个点所属哪个区域范围内管辖，突然想起来三年前做了个外卖的项目里面有个功能，判断用户是否在商家自己划的配送范围内，又找回来以前的代码来看了下，所以在此处记录一下

@Data

@NoArgsConstructor

@AllArgsConstructor

public class Point {

private Double lat;

private Double lng;

}

/**

* 判断当前位置是否在多边形区域内

*

* @param checkPoint 当前经纬度

* @param areaAround 围栏范围

* @return

*/

public static boolean checkIsInPolygon(Point checkPoint, List areaAround) {

Point2D.Double point = new Point2D.Double(checkPoint.getLat(), checkPoint.getLng());

List pointList = new ArrayList<>();

for (Point everyPoint : areaAround) {

Point2D.Double polygonPoint = new Point2D.Double(everyPoint.getLat(), everyPoint.getLng());

pointList.add(polygonPoint);

}

return checkIsPtInPoly(point, pointList);

}

/**

* 判断点是否在多边形内，如果点位于多边形的顶点或边上，也算做点在多边形内，直接返回true

*

* @param point 检测点

* @param pts 多边形的顶点

* @return 点在多边形内返回true, 否则返回false

*/

public static boolean checkIsPtInPoly(Point2D.Double point, List pts) {

int N = pts.size();

//如果点位于多边形的顶点或边上，也算做点在多边形内，直接返回true

boolean boundOrVertex = true;

//cross points count of x

int intersectCount = 0;

//浮点类型计算时候与0比较时候的容差

double precision = 2e-10;

//neighbour bound vertices

Point2D.Double p1, p2;

//当前点

Point2D.Double p = point;

//left vertex

p1 = pts.get(0);

//check all rays

for (int i = 1; i <= N; ++i) {

if (p.equals(p1)) {

//p is an vertex

return boundOrVertex;

}

//right vertex

p2 = pts.get(i % N);

//ray is outside of our interests

if (p.x < Math.min(p1.x, p2.x) || p.x > Math.max(p1.x, p2.x)) {

p1 = p2;

//next ray left point

continue;

}

//ray is crossing over by the algorithm (common part of)

if (p.x > Math.min(p1.x, p2.x) && p.x < Math.max(p1.x, p2.x)) {

//x is before of ray

if (p.y <= Math.max(p1.y, p2.y)) {

//overlies on a horizontal ray

if (p1.x == p2.x && p.y >= Math.min(p1.y, p2.y)) {

return boundOrVertex;

}

//ray is vertical

if (p1.y == p2.y) {

//overlies on a vertical ray

if (p1.y == p.y) {

return boundOrVertex;

//before ray

} else {

++intersectCount;

}

} else {

//cross point on the left side

//cross point of y

double xinters = (p.x - p1.x) * (p2.y - p1.y) / (p2.x - p1.x) + p1.y;

//overlies on a ray

if (Math.abs(p.y - xinters) < precision) {

return boundOrVertex;

}

//before ray

if (p.y < xinters) {

++intersectCount;

}

}

}

} else {

//special case when ray is crossing through the vertex

//p crossing over p2

if (p.x == p2.x && p.y <= p2.y) {

//next vertex

Point2D.Double p3 = pts.get((i + 1) % N);

//p.x lies between p1.x & p3.x

if (p.x >= Math.min(p1.x, p3.x) && p.x <= Math.max(p1.x, p3.x)) {

++intersectCount;

} else {

intersectCount += 2;

}

}

}

//next ray left point

p1 = p2;

}

//偶数在多边形外

if (intersectCount % 2 == 0) {

return false;

} else {

//奇数在多边形内

return true;

}

}

还是三年前写的，先记录一下，抽时间再优化一下代码