Wrong polyline drawing on map with Google Maps SDK - ios

Question

I'm trying to draw route on my map using Google Maps SDK.
This is the URL that i'm calling and I parse the JSON response to array of coordinates:
id jsonResponse = [NSJSONSerialization JSONObjectWithData:responseObject options:NSJSONReadingMutableContainers error:nil];
int points_count = 0;
points_count = [[[[[[jsonResponse objectForKey:#"routes"] objectAtIndex:0] objectForKey:#"legs"] objectAtIndex:0] objectForKey:#"steps"] count];
NSArray *steps = nil;
if (points_count && [[[[jsonResponse objectForKey:#"routes"] objectAtIndex:0] objectForKey:#"legs"] count])
{
steps = [[[[[jsonResponse objectForKey:#"routes"] objectAtIndex:0] objectForKey:#"legs"] objectAtIndex:0] objectForKey:#"steps"];
}
NSMutableArray *coordinates = [[NSMutableArray alloc] initWithCapacity:points_count];
for (int i = 0; i < points_count; i++)
{
NSDictionary *start;
NSDictionary *finish;
double st_lat = [[[[steps objectAtIndex:i] objectForKey:#"start_location"] valueForKey:#"lat"] doubleValue];
double st_lon = [[[[steps objectAtIndex:i] objectForKey:#"start_location"] valueForKey:#"lng"] doubleValue];
if (st_lat > 0.0f && st_lon > 0.0f)
{
start = #{ #"latitude" : [NSNumber numberWithDouble:st_lat], #"longitude" : [NSNumber numberWithDouble:st_lon] };
}
double end_lat = [[[[steps objectAtIndex:i] objectForKey:#"end_location"] valueForKey:#"lat"] doubleValue];
double end_lon = [[[[steps objectAtIndex:i] objectForKey:#"end_location"] valueForKey:#"lng"] doubleValue];
if (end_lat > 0.0f && end_lon > 0.0f)
{
finish = #{ #"latitude" : [NSNumber numberWithDouble:end_lat], #"longitude" : [NSNumber numberWithDouble:end_lon] };
}
[coordinates addObject:#{ #"start" : start, #"finish" : finish }];
}
And than drawing on the map view with this method:
GMSMutablePath *path = [GMSMutablePath path];
for (NSDictionary *d in directions)
{
NSDictionary *start = d[#"start"];
NSDictionary *finish = d[#"finish"];
CLLocationCoordinate2D c_start = CLLocationCoordinate2DMake([start[#"latitude"] doubleValue], [start[#"longitude"] doubleValue]);
CLLocationCoordinate2D c_finish = CLLocationCoordinate2DMake([finish[#"latitude"] doubleValue], [finish[#"longitude"] doubleValue]);
[path addCoordinate:c_start];
[path addCoordinate:c_finish];
}
GMSPolyline *line = [GMSPolyline polylineWithPath:path];
line.strokeColor = [UIColor redColor];
line.strokeWidth = 2.0f;
line.map = self.mapView;
Why it is drawing like that and not going into the street it self?
What am I doing wrong here?

Answer 1

Try this it draws exact path like in driving mode - StreetMode, Here's my code :
iOS GSMPolyLine

Answer 2

So the problem was that I used the start_location and end_location instead of the polyline -> points. Fixed my code into this:
Request URL for example: https://maps.googleapis.com/maps/api/directions/json?origin=40.716072,-74.008836&destination=40.697545,-73.983892&sensor=false&waypoints=optimize:true&mode=driving
id jsonResponse = [NSJSONSerialization JSONObjectWithData:responseObject options:NSJSONReadingMutableContainers error:nil];
int points_count = 0;
points_count = [[[[[[jsonResponse objectForKey:#"routes"] objectAtIndex:0] objectForKey:#"legs"] objectAtIndex:0] objectForKey:#"steps"] count];
NSArray *steps = nil;
if (points_count && [[[[jsonResponse objectForKey:#"routes"] objectAtIndex:0] objectForKey:#"legs"] count])
{
steps = [[[[[jsonResponse objectForKey:#"routes"] objectAtIndex:0] objectForKey:#"legs"] objectAtIndex:0] objectForKey:#"steps"];
}
NSMutableArray *coordinates = [[NSMutableArray alloc] initWithCapacity:points_count];
for (int i = 0; i < points_count; i++)
{
NSString *toDecode = [[[steps objectAtIndex:i] objectForKey:#"polyline"] valueForKey:#"points"];
NSArray *locations = [AppUtils decodePolylineWithString:toDecode];
for (int i = 0 ; i < locations.count ; i++)
{
if (i != locations.count - 1) {
CLLocation *start = [locations objectAtIndex:i];
CLLocation *finish = [locations objectAtIndex:i + 1];
[coordinates addObject:#{ #"start" : start, #"finish" : finish }];
}
}
}
GMSMutablePath *path = [GMSMutablePath path];
for (NSDictionary *d in directions)
{
CLLocation *start = d[#"start"];
CLLocation *finish = d[#"finish"];
[path addCoordinate:start.coordinate];
[path addCoordinate:finish.coordinate];
}
GMSPolyline *line = [GMSPolyline polylineWithPath:path];
line.strokeColor = [UIColor redColor];
line.strokeWidth = 2.0f;
line.map = self.mapView;
+ (NSArray*)decodePolylineWithString:(NSString *)encodedString
{
NSMutableArray *coordinates = [NSMutableArray array];
const char *bytes = [encodedString UTF8String];
NSUInteger length = [encodedString lengthOfBytesUsingEncoding:NSUTF8StringEncoding];
NSUInteger idx = 0;
NSUInteger count = length / 4;
CLLocationCoordinate2D *coords = calloc(count, sizeof(CLLocationCoordinate2D));
NSUInteger coordIdx = 0;
float latitude = 0;
float longitude = 0;
while (idx < length) {
char byte = 0;
int res = 0;
char shift = 0;
do {
byte = bytes[idx++] - 63;
res |= (byte & 0x1F) << shift;
shift += 5;
} while (byte >= 0x20);
float deltaLat = ((res & 1) ? ~(res >> 1) : (res >> 1));
latitude += deltaLat;
shift = 0;
res = 0;
do {
byte = bytes[idx++] - 0x3F;
res |= (byte & 0x1F) << shift;
shift += 5;
} while (byte >= 0x20);
float deltaLon = ((res & 1) ? ~(res >> 1) : (res >> 1));
longitude += deltaLon;
float finalLat = latitude * 1E-5;
float finalLon = longitude * 1E-5;
CLLocationCoordinate2D coord = CLLocationCoordinate2DMake(finalLat, finalLon);
coords[coordIdx++] = coord;
CLLocation *location = [[CLLocation alloc] initWithLatitude:finalLat longitude:finalLon];
[coordinates addObject:location];
if (coordIdx == count) {
NSUInteger newCount = count + 10;
coords = realloc(coords, newCount * sizeof(CLLocationCoordinate2D));
count = newCount;
}
}
free(coords);
return coordinates;
}
I know it's a little bit dirty, but that's work and it works great.
Enjoy.