Question

我想检查谷歌地图上的新折线A绘图是否接触或重叠到任何先前绘制的折线（B，C，D ......）。在搜索解决方案期间，我得到了如下算法

  Polyline findExistingPolyline(Polyline[] polylines, Polyline polyline) {
  LatLng[] polylinePoints = PolylineDecoder.toLatLng(polyline);
  for (Polyline existing: polylines) {
     LatLng[] existingPoints = PolylineDecoder.toLatLng(existing);
     if (isMostlyCovered(existingPoints , polylinePoints)) {
        return existing;
     }
   }

   return null;

  }

   boolean isMostlyCovered(LatLng[] existingPoints, LatLng[] polylinePoints) {
   int initialSize = polylinePoints.length;
   for (LatLng point: polylinePoints) {
     for (LatLng existingPoint: existingPoints) {
        if (distanceBetween(existingPoint, point) <= 100) {
          polylinePoints.remove();// I actually use iterator, here it is just demosnstration
        }
     }
   }
   // check how many points are left and decide if polyline is mostly covered
   // if 90% of the points is removed - existing polylines covers new polyline
   return (polylinePoints.length * 100 / initialSize) <= 10;
  }

在这个算法中，一个PolylineDecoder类将一条折线传递给它所使用的方法，后来我发现这个类在多个链接上，但几乎在每个地方都接收到一个不是折线的字符串

public class PolylineDecoder {


public static ArrayList decodePoly(String encoded) {
  ArrayList poly = new ArrayList();
  int index = 0, len = encoded.length();
  int lat = 0, lng = 0;
  while (index < len) {
   int b, shift = 0, result = 0;
   do {
    b = encoded.charAt(index++) - 63;
    result |= (b & 0x1f) << shift;
    shift += 5;
   } while (b >= 0x20);
   int dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
   lat += dlat;
   shift = 0;
   result = 0;
   do {
    b = encoded.charAt(index++) - 63;
    result |= (b & 0x1f) << shift;
    shift += 5;
   } while (b >= 0x20);
   int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
   lng += dlng;
   Location p = new Location((((double) lat / 1E5)),
     (((double) lng / 1E5)));
   poly.add(p);
  }
  return poly;
 }
}

所以我把折线转换成字符串并将其传递给PolylineDecoder类

LatLng[] polylinePoints = PolylineDecoder.toLatLng(polyline.toString());

现在，当我运行程序时，它会在PolylineDecoder类中为第二行do while循环提供异常（字符串out of bound of exception）

b = encoded.charAt(index++) - 63;

我该如何处理此异常或者是否错过了一些中间步骤？感谢

Answer 1

我们应该忽略在String poly line中找到的任何Java文字。可以使用

完成

StringEscapeUtils.unescapeJava(polyline)

以上内容可以改为

polyline  = StringEscapeUtils.unescapeJava(polyline.toString());
LatLng[] polylinePoints = PolylineDecoder.toLatLng(polyline);

在android中解码折线

1 个答案: