public boolean isPointInPolygon(double px, double py, ArrayList<Double> polygonXA, ArrayList<Double> polygonYA) {
boolean isInside = false;
double ESP = 1e-9;
int count = 0;
double linePoint1x;
double linePoint1y;
double linePoint2x = 180;
double linePoint2y;
linePoint1x = px;
linePoint1y = py;
linePoint2y = py;
for (int i = 0; i < polygonXA.size() - 1; i++) {
double cx1 = polygonXA.get(i);
double cy1 = polygonYA.get(i);
double cx2 = polygonXA.get(i + 1);
double cy2 = polygonYA.get(i + 1);
if (isPointOnLine(px, py, cx1, cy1, cx2, cy2)) {
return true;
}
if (Math.abs(cy2 - cy1) < ESP) {
continue;
}
if (isPointOnLine(cx1, cy1, linePoint1x, linePoint1y, linePoint2x, linePoint2y)) {
if (cy1 > cy2)
count++;
} else if (isPointOnLine(cx2, cy2, linePoint1x, linePoint1y, linePoint2x, linePoint2y)) {
if (cy2 > cy1)
count++;
} else if (isIntersect(cx1, cy1, cx2, cy2, linePoint1x, linePoint1y, linePoint2x, linePoint2y)) {
count++;
}
}
if (count % 2 == 1) {
isInside = true;
}
return isInside;
}
public static double Multiply(double px0, double py0, double px1, double py1, double px2, double py2) {
return ((px1 - px0) * (py2 - py0) - (px2 - px0) * (py1 - py0));
}
public boolean isPointOnLine(double px0, double py0, double px1, double py1, double px2, double py2) {
boolean flag = false;
double ESP = 1e-9;
if ((Math.abs(Multiply(px0, py0, px1, py1, px2, py2)) < ESP) && ((px0 - px1) * (px0 - px2) <= 0)
&& ((py0 - py1) * (py0 - py2) <= 0)) {
flag = true;
}
return flag;
}
public boolean isIntersect(double px1, double py1, double px2, double py2, double px3, double py3, double px4,
double py4) {
boolean flag = false;
double d = (px2 - px1) * (py4 - py3) - (py2 - py1) * (px4 - px3);
if (d != 0) {
double r = ((py1 - py3) * (px4 - px3) - (px1 - px3) * (py4 - py3)) / d;
double s = ((py1 - py3) * (px2 - px1) - (px1 - px3) * (py2 - py1)) / d;
if ((r >= 0) && (r <= 1) && (s >= 0) && (s <= 1)) {
flag = true;
}
}
return flag;
}
下面方法调用：
public void isInply(){
double px = 113.705835;
double py = 34.787479;
ArrayList<Double> polygonXA = new ArrayList<Double>();
ArrayList<Double> polygonYA = new ArrayList<Double>();
polygonXA.add(113.700213);// 北京
polygonXA.add(113.706651);// 石家庄
polygonXA.add(113.706608);// 德州
polygonXA.add(113.707337);// 天津
polygonXA.add(113.701587);// 烟台
polygonXA.add(113.700128);// 唐山jdal
polygonYA.add(34.791532);
polygonYA.add(34.791568);
polygonYA.add(34.789242);
polygonYA.add(34.786633);
polygonYA.add(34.786669);
polygonYA.add(34.789242);
boolean isFlag = isPointInPolygon(px,py,polygonXA,polygonYA);
}
出自：http://blog.163.com/kangle0925@126/blog/static/27758198201181484115912/
