我使用dart / flutter和'package:latlong/latlong.dart'将GPX文件解析为LatLng对象列表。一切正常，但是下一步是找到路线的总距离。
这里的问题是
如何从列表中的LatLng对象获取总距离 飞镖？
我以前在Java中使用过Haversine公式，但是不确定使用Dart实现它的最佳方法。任何建议的帮助将不胜感激。
修改
以下是尝试根据以下答案获得总距离的方法。由于某种原因，它不会添加到totalDistance中，并且不会返回双精度值。
下面假设要遍历60个以上的LatLng对象的列表，并找到每个对象之间的距离，并添加一个totalDistance double，该double在循环末尾返回。
static double getDistanceFromGPSPointsInRoute(List<LatLng> gpsList) {
double totalDistance = 0.0;
for (var i = 0; i < gpsList.length; i++) {
var p = 0.017453292519943295;
var c = cos;
var a = 0.5 -
c((gpsList[i + 1].latitude - gpsList[i].latitude) * p) / 2 +
c(gpsList[i].latitude * p) *
c(gpsList[i + 1].latitude * p) *
(1 - c((gpsList[i + 1].longitude - gpsList[i].longitude) * p)) /
2;
double distance = 12742 * asin(sqrt(a));
totalDistance += distance;
print('Distance is ${12742 * asin(sqrt(a))}');
}
print('Total distance is $totalDistance');
return totalDistance;
}
输出
flutter: Distance is 0.004143962775784678
flutter: Distance is 0.0041439635323316775
flutter: Distance is 0.007796918986828574
flutter: Distance is 0.007285385943437824
flutter: Distance is 0.006890844300938902
flutter: Distance is 0.006353952460010352
flutter: Distance is 0.005560051252981138
如上所述，这里没有提及总距离。
LatLng列表示例
flutter: -36.84975 , 174.646685
flutter: -36.849692 , 174.646497
flutter: -36.84967 , 174.646436
flutter: -36.849578 , 174.646264
flutter: -36.849502 , 174.646164
flutter: -36.849367 , 174.646038
flutter: -36.849209 , 174.645959
flutter: -36.849155 , 174.64594
flutter: -36.849107 , 174.645932
flutter: -36.849058 , 174.645922
flutter: -36.848952 , 174.645895
flutter: -36.84886 , 174.645906
flutter: -36.84879 , 174.645913
flutter: -36.848748 , 174.645836
flutter: -36.848744 , 174.645802
答案 0 :(得分：3)
请尝试一下。我使用Google Maps进行了测试，并且可以正常工作。您可以进行循环并通过每次使用2个点来找到总距离。 我添加了一些随机的虚拟数据以演示其工作原理。将此代码复制到https://dartpad.dartlang.org/并轻松进行测试。
import 'dart:math' show cos, sqrt, asin;
void main() {
double calculateDistance(lat1, lon1, lat2, lon2){
var p = 0.017453292519943295;
var c = cos;
var a = 0.5 - c((lat2 - lat1) * p)/2 +
c(lat1 * p) * c(lat2 * p) *
(1 - c((lon2 - lon1) * p))/2;
return 12742 * asin(sqrt(a));
}
List<dynamic> data = [
{
"lat": 44.968046,
"lng": -94.420307
},{
"lat": 44.33328,
"lng": -89.132008
},{
"lat": 33.755787,
"lng": -116.359998
},{
"lat": 33.844843,
"lng": -116.54911
},{
"lat": 44.92057,
"lng": -93.44786
},{
"lat": 44.240309,
"lng": -91.493619
},{
"lat": 44.968041,
"lng": -94.419696
},{
"lat": 44.333304,
"lng": -89.132027
},{
"lat": 33.755783,
"lng": -116.360066
},{
"lat": 33.844847,
"lng": -116.549069
},
];
double totalDistance = 0;
for(var i = 0; i < data.length-1; i++){
totalDistance += calculateDistance(data[i]["lat"], data[i]["lng"], data[i+1]["lat"], data[i+1]["lng"]);
}
print(totalDistance);
}
答案 1 :(得分：3)
使用库latlong进行常见的纬度和经度计算。 这同时支持“ Haversine”算法和“ Vincenty”算法。
List<dynamic> data = [
{
"lat": 44.968046,
"lng": -94.420307
},
...
];
final Distance distance = Distance();
double totalDistanceInM = 0;
double totalDistanceInKm = 0;
for(var i = 0; i < data.length - 1; i++){
totalDistanceInM += distance(
LatLng(data[i]["lat"], data[i]["lng"]),
LatLng(data[i+1]["lat"], data[i+1]["lng"])
);
totalDistanceInKm += distance.as(
LengthUnit.Kilometer,
LatLng(data[i]["lat"], data[i]["lng"]),
LatLng(data[i+1]["lat"], data[i+1]["lng"]),
);
}
答案 2 :(得分：1)
我使用了westdabestdb的答案。没关系。
而且，您也可以使用geolocator插件。
Geolocator.distanceBetween(lat1, lon1, lat2, lon2);
答案 3 :(得分：0)
此功能计算两个点之间的距离（根据这些点的纬度/经度）。
unit = the unit you desire for results
where: 'M' is statute miles (default)
'K' is kilometers
'N' is nautical miles
String distance(
double lat1, double lon1, double lat2, double lon2, String unit) {
double theta = lon1 - lon2;
double dist = sin(deg2rad(lat1)) * sin(deg2rad(lat2)) +
cos(deg2rad(lat1)) * cos(deg2rad(lat2)) * cos(deg2rad(theta));
dist = acos(dist);
dist = rad2deg(dist);
dist = dist * 60 * 1.1515;
if (unit == 'K') {
dist = dist * 1.609344;
} else if (unit == 'N') {
dist = dist * 0.8684;
}
return dist.toStringAsFixed(2);
}
double deg2rad(double deg) {
return (deg * pi / 180.0);
}
double rad2deg(double rad) {
return (rad * 180.0 / pi);
}
void main() {
print("Distance : " + distance(32.9697, -96.80322, 29.46786, -98.53506, 'K'));
}
答案 4 :(得分：0)
如果在当前位置搜索的情况下，我还使用vector_math将度数转换为弧度，还使用geolocator获得当前用户的纬度和经度可以直接通过 Geolocator.distanceBetween（startLatitude，startLongitude，endLatitude，endLongitude）来计算两个位置之间的距离。
import 'dart:math' show sin, cos, sqrt, atan2;
import 'package:vector_math/vector_math.dart';
import 'package:geolocator/geolocator.dart';
Position _currentPosition;
double earthRadius = 6371000;
//Using pLat and pLng as dummy location
double pLat = 22.8965265; double pLng = 76.2545445;
//Use Geolocator to find the current location(latitude & longitude)
getUserLocation() async {
_currentPosition = await GeoLocator.getCurrentPosition(desiredAccuracy: LocationAccuracy.high);
}
//Calculating the distance between two points without Geolocator plugin
getDistance(){
var dLat = radians(pLat - _currentPosition.latitude);
var dLng = radians(pLng - _currentPosition.longitude);
var a = sin(dLat/2) * sin(dLat/2) + cos(radians(_currentPosition.latitude))
* cos(radians(pLat)) * sin(dLng/2) * sin(dLng/2);
var c = 2 * atan2(sqrt(a), sqrt(1-a));
var d = earthRadius * c;
print(d); //d is the distance in meters
}
//Calculating the distance between two points with Geolocator plugin
getDistance(){
final double distance = Geolocator.distanceBetween(pLat, pLng,
_currentPosition.latitude, _currentPosition.longitude);
print(distance);
}
答案 5 :(得分：-1)
在pubyml中添加地理定位器：^7.1.1
//获取当前经纬度
var currentLocation = myLocation; 动态坐标 = 新坐标(myLocation.latitude, myLocation.longitude);
//获取米距离
//Latitude2 和 Longitude2 可以到任何地方测量距离
double distanceInMeters = Geolocator.distanceBetween(Latitude1, Longitude1, Latitude2, Longitude2);