java 判断范围_java判断一个点是否在一个围栏范围内
應(yīng)項(xiàng)目需求，需要判斷一個(gè)點(diǎn)所屬哪個(gè)區(qū)域范圍內(nèi)管轄，突然想起來三年前做了個(gè)外賣的項(xiàng)目里面有個(gè)功能，判斷用戶是否在商家自己劃的配送范圍內(nèi)，又找回來以前的代碼來看了下，所以在此處記錄一下
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Point {
private Double lat;
private Double lng;
}
/**
* 判斷當(dāng)前位置是否在多邊形區(qū)域內(nèi)
*
* @param checkPoint 當(dāng)前經(jīng)緯度
* @param areaAround 圍欄范圍
* @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);
}
/**
* 判斷點(diǎn)是否在多邊形內(nèi)，如果點(diǎn)位于多邊形的頂點(diǎn)或邊上，也算做點(diǎn)在多邊形內(nèi)，直接返回true
*
* @param point 檢測點(diǎn)
* @param pts 多邊形的頂點(diǎn)
* @return 點(diǎn)在多邊形內(nèi)返回true, 否則返回false
*/
public static boolean checkIsPtInPoly(Point2D.Double point, List pts) {
int N = pts.size();
//如果點(diǎn)位于多邊形的頂點(diǎn)或邊上，也算做點(diǎn)在多邊形內(nèi)，直接返回true
boolean boundOrVertex = true;
//cross points count of x
int intersectCount = 0;
//浮點(diǎn)類型計(jì)算時(shí)候與0比較時(shí)候的容差
double precision = 2e-10;
//neighbour bound vertices
Point2D.Double p1, p2;
//當(dāng)前點(diǎn)
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;
}
//偶數(shù)在多邊形外
if (intersectCount % 2 == 0) {
return false;
} else {
//奇數(shù)在多邊形內(nèi)
return true;
}
}
還是三年前寫的，先記錄一下，抽時(shí)間再優(yōu)化一下代碼
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