Android的检查，如果我的纬度/经度位置withing给定区域 [英] Android check if my lat/lng position withing a given area

问题描述

假设我有以下的纬度/经度创建区域的地图多边形

Suppose I have the following lat/lng that creates a polygon of area in map

39.888932, -95.557237
42.156511, -101.347921
40.322707, -101.040304
38.299884, -100.447042
36.731433, -96.623800

现在我怎么能检查 40.356203，-97.304952 这个纬度/经度是给定区域内或没有。

Now How can I check if 40.356203, -97.304952 this lat/lng is within that given area or not.

我怎样才能做到这一点？

How can I do this??

推荐答案

刚试过光线投射算法，识别多边形点。这完美的作品。

Just tried Ray Casting algorithm which identifies point in polygon. This works perfect.

http://en.wikipedia.org/wiki/Point_in_polygon 雷的论文-Casting

Refer http://en.wikipedia.org/wiki/Point_in_polygon for thesis of Ray-Casting

private boolean isPointInPolygon(LatLng tap, ArrayList<LatLng> vertices) {
        int intersectCount = 0;
        for (int j = 0; j < vertices.size() - 1; j++) {
            if (rayCastIntersect(tap, vertices.get(j), vertices.get(j + 1))) {
                intersectCount++;
            }
        }

        return ((intersectCount % 2) == 1); // odd = inside, even = outside;
    }

    private boolean rayCastIntersect(LatLng tap, LatLng vertA, LatLng vertB) {

        double aY = vertA.latitude;
        double bY = vertB.latitude;
        double aX = vertA.longitude;
        double bX = vertB.longitude;
        double pY = tap.latitude;
        double pX = tap.longitude;

        if ((aY > pY && bY > pY) || (aY < pY && bY < pY)
                || (aX < pX && bX < pX)) {
            return false; // a and b can't both be above or below pt.y, and a or
                            // b must be east of pt.x
        }

        double m = (aY - bY) / (aX - bX); // Rise over run
        double bee = (-aX) * m + aY; // y = mx + b
        double x = (pY - bee) / m; // algebra is neat!

        return x > pX;
    }

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