数学公式

/**
* 计算当前点到线的垂线距离
*
* @param p 当前点
* @param lineBegin 线的起点
* @param lineEnd 线的终点
*/
private static double calculateDistanceFromPoint(LatLng p, LatLng lineBegin,
LatLng lineEnd) {
double A = p.longitude - lineBegin.longitude;
double B = p.latitude - lineBegin.latitude;
double C = lineEnd.longitude - lineBegin.longitude;
double D = lineEnd.latitude - lineBegin.latitude;

    double dot = A * C + B * D;
    double len_sq = C * C + D * D;
    double param = dot / len_sq;

    double xx, yy;

    if (param < 0 || (lineBegin.longitude == lineEnd.longitude
            && lineBegin.latitude == lineEnd.latitude)) {
        xx = lineBegin.longitude;
        yy = lineBegin.latitude;

// return -1;
} else if (param > 1) {
xx = lineEnd.longitude;
yy = lineEnd.latitude;
// return -1;
} else {
xx = lineBegin.longitude + param * C;
yy = lineBegin.latitude + param * D;
}
return AMapUtils.calculateLineDistance(p, new LatLng(yy, xx));
}