判断点是否在多边形内

As per my requirement, I am drawing polygons on google map shown in the image below.(using maps v2)

现在我需要在用户输入该特定多边形时显示警报。

如何确定我的当前位置是否在多边形内。 （需要优化方式而不耗尽电池）

提前致谢。

刚刚尝试了识别多边形中的点的射线投射算法。这很完美。

Refer http://en.wikipedia.org/wiki/Point_in_polygon http://en.wikipedia.org/wiki/Point_in_polygon光线投射论文

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;
    }