Recently l have been thinking about this as well. I have found this project https://github.com/googlemaps/android-maps-utils and created a jar from part of this project. I also added a function to find coordinates on the polyline where a line drawn from current location, perpendicular to the polyline, intersects the polyline - this makes updated polyline look better if current location is a couple of meters of the path (polyline) which depends on the GPS accuracy etc.
#AdditionalJar: mapsutil
Sub Globals
Dim pline As Polyline
Dim gmap As GoogleMap
Dim LastLoc, DestLoc As LatLng
End SubSub GetDirections(source As String, destination As String)
Dim j As HttpJob
Dim API_KEY As String = "YOUR API KEY" 'directions api key
' Get directions (Location source -> Location destination)
j.Initialize("Directions", Me)
j.Download2("https://maps.googleapis.com/maps/api/directions/json", Array As String("origin", source,"destination", destination,"key",API_KEY))
Wait For (j) JobDone(j As HttpJob)
If j.Success Then
Dim parser As JSONParser
parser.Initialize(j.GetString)
Dim root As Map = parser.NextObject
If root.Get("status") = "OK" Then
Dim routes As List = root.Get("routes")
For Each colroutes As Map In routes
Dim legs As List = colroutes.Get("legs")
For Each collegs As Map In legs
start_address = collegs.Get("start_address")
end_address = collegs.Get("end_address")
Dim steps As List = collegs.Get("steps")
For Each colsteps As Map In steps
Dim duration As Map = colsteps.Get("duration")
travelduration = travelduration + duration.Get("value")
Dim distance As Map = colsteps.Get("distance")
traveldistance = traveldistance + distance.Get("value")
Next
Dim overview_polyline As Map = colroutes.Get("overview_polyline")
polyPoints = overview_polyline.Get("points")
Next
Next
j.Release
drawDirections 'draw polyline
Else
ToastMessageShow("Error: " & root.Get("status"), True)
End If
Else
Log("Error!")
End If
j.Release
End SubSub drawDirections
Dim jo As JavaObject
Dim Points As List
Points.Initialize
jo.InitializeStatic("com.poly.PolyUtil")
Points = jo.RunMethod("decode", Array(polyPoints))
If Points.Size > 0 Then
pline = gmap.AddPolyline
pline.Points = Points
pline.Color = Colors.Magenta
End If
End SubSub updateDirections
Dim source, destination As String
Dim jo As JavaObject
Dim Points As List
Dim res As Int
Dim curloc As LatLng
curloc.Initialize(LastLoc.Latitude, LastLoc.Longitude)
Points.Initialize
jo.InitializeStatic("com.poly.PolyUtil")
Points = pline.Points
Dim tolerance As Double
tolerance = 10 '10 m
res = jo.RunMethod("locationIndexOnPath", Array(curloc, Points, False, tolerance)) 'checks whether the given point lies on or near a polyline, within a specified tolerance in meters
'returns -1 if point does not lie on or near the polyline.
' 0 if point is between poly[0] and poly[1] (inclusive),
' 1 if between poly[1] and poly[2],
' 2 if between poly[2] and poly[3],
' ...etc
Dim res1 As Double
Dim p1, p2 As LatLng
Dim pathdata As String
p1.Initialize(LastLoc.Latitude, LastLoc.Longitude)
pathdata = pathdata & "last loc " & LastLoc.Latitude & ", " & LastLoc.Longitude & CRLF
If res = -1 Then 'not on path
source = LastLoc.Latitude & "," & LastLoc.Longitude 'current location from GPS_LocationChanged sub
destination = DestLoc.Latitude & "," & DestLoc.Longitude 'destination location coordinates
p2 = Points.Get(0)
GetDirections(source, destination) 'get new directions
Else 'on path, res = index in Points list (polyline)
p2 = Points.Get(res)
If res = 0 Then '0 so it is the first item in the Points list (polyline)
Dim resll As LatLng
jo.InitializeStatic("com.poly.PolyUtil")
resll = jo.RunMethod("intersectOnLine", Array(curloc, Points.Get(0), Points.Get(1))) 'find coordinates on the polyline where current location intersects with polyline
If resll.Latitude <> 0 And resll.Longitude <> 0 Then 'resl1 equals to coordinates on the polyline, if current loc. intesects with polyline path
'res11 = 0,0 - current location doesn't intersect with the polyine,
Points.Set(0, resll)
pline.Points = Points
pline.Color = Colors.Red
End If
Else '>0 so, remove polyline points from the Points list and update polyline
If Points.Size > 2 Then
For i = 0 To res - 1
Points.RemoveAt(0)
Next
pline.Points = Points 'set polyline
pline.Color = Colors.Green
End If
End If
End If
End Sub
You should be more specific what you want? Not everybody uses UBER application to understand what you mean?
