how to get real direction steps using Flutter? (draw real route) - google-maps

Question

I'm working with taxi app. Is it possible to draw real route on real road using flutter?
I used this way: https://developers.google.com/maps/documentation/directions/intro#ExampleRequests
getDirectionSteps(double destinationLat, double destinationLng) {
network
.get("origin=" +
location.latitude.toString() +
"," +
location.longitude.toString() +
"&destination=" +
destinationLat.toString() +
"," +
destinationLng.toString() +
"&key=api_key")
.then((dynamic res) {
List<Steps> rr = res;
print(res.toString());
ccc = new List();
for (final i in rr) {
ccc.add(i.startLocation);
ccc.add(i.endLocation);
}
mapView.onMapReady.listen((_) {
mapView.setMarkers(getMarker(location.latitude,location.longitude,destinationLat,destinationLng));
mapView.addPolyline(new Polyline("12", ccc, width: 15.0));
});
_screenListener.dismissLoader();
showMap();
}).catchError((Exception error) => _screenListener.dismissLoader());
}
my output look like this:
But I need like this: (draw destination route on real road)

Answer 1

to find the exact route you have to get points out of the polylineoverview from the json from directions api.
This is how I extracted the exact route just like you show in the second image.
Its is a function that return points as a string
Future<String> getRouteCoordinates(LatLng l1, LatLng l2) async {
String url =
"https://maps.googleapis.com/maps/api/directions/json?origin=${l1.latitude},${l1.longitude}&destination=${l2.latitude},${l2.longitude}&key=${Constants.anotherApiKey}";
http.Response response = await http.get(url);
Map values = jsonDecode(response.body);
ProjectLog.logIt(TAG, "Predictions", values.toString());
return values["routes"][0]["overview_polyline"]["points"];
}
you will get a string of points somewhat similiar to this
u|umDs`gwML}A_GGgFGAWwDEm#TcFGsAAa#BeA\QDe#AYISOKHKJGFw#^?jAAnAEnOA|GAhHEx#?jA#tC?XFLLf#Bf##t#?xAA|E?dEEj_#GxMChG#tCIvl##tAK`DQlA?zBApE?lBExNAlH#rMAtGJdDJnATfB`AnEdAzEj#~B|#lEF\xAvGnAlF~#lEv#`DvAxFxAxGzCdN`H`ZnEnRr#hDnB|IhDlNvKnd#vDhPrFzUzGjYxBtH|#hCdAzBXl#fAhBtAtBjBhCfArAdAhAvBtBlB|AjGfFhLzJfEzDzCvDz#pA`BpC`ApBbAzBxCrIr#rBjNta#x#nBbAlBzCbI|R|j#hA`FBVC`ASpD?lA[FiMpCaBVgABiAPoE~#cIdBiLfCcHdBsCl#yJvBmDt#y#l#{#X_#P[VGJGZCd#r#tCf#rBTbAV`BB`#?n#GdA#XHj#bAxBl#hBPjADf#?v#Ej#Ml#Ut#[r#]h#sA`C{#lAMZGl#KjECbDGhBuGMsJKcCGw#CqJCiECAd#ALoBbKs#jDM^x#j#vPfLvCnB~DnCx#f#R#RAd#GDIbBmDv#y#LId#On#A~EJX#pDJrADb#QFC
Now you will add the polyline in the set of polylines like this
_polyLines.add(Polyline(
polylineId: PolylineId(Constants.currentRoutePolylineId),//pass any string here
width: 3,
geodesic: true,
points: Utils.convertToLatLng(Utils.decodePoly(encodedPoly)),
color: ConstantColors.PrimaryColor));
here encodedPoly is the same string that extracted from previous method.
In the function above you have to convert the points\encodedPoly into the list of latlng. Like i did using utils function.
Both functions that i used are
decodePoly :
// !DECODE POLY
static List decodePoly(String poly) {
var list = poly.codeUnits;
var lList = new List();
int index = 0;
int len = poly.length;
int c = 0;
// repeating until all attributes are decoded
do {
var shift = 0;
int result = 0;
// for decoding value of one attribute
do {
c = list[index] - 63;
result |= (c & 0x1F) << (shift * 5);
index++;
shift++;
} while (c >= 32);
/* if value is negative then bitwise not the value */
if (result & 1 == 1) {
result = ~result;
}
var result1 = (result >> 1) * 0.00001;
lList.add(result1);
} while (index < len);
/*adding to previous value as done in encoding */
for (var i = 2; i < lList.length; i++) lList[i] += lList[i - 2];
print(lList.toString());
return lList;
}
and convertToLatLng() :
static List<LatLng> convertToLatLng(List points) {
List<LatLng> result = <LatLng>[];
for (int i = 0; i < points.length; i++) {
if (i % 2 != 0) {
result.add(LatLng(points[i - 1], points[i]));
}
}
return result;
}
This would make a exact route like i did in my app :
Here is the screenshot :