How to effectively draw Polyline using Google API?

i'm drawing polyline on MapView using "google direction API" and getting success in it.But the thing is that it draws straight line between two locations(with their longitude and latitude).I don't know how to dra开发者_如何学Gow line effectively like shown by google maps,when we click "get directions" between two locations.

I suggest taking a look at an SDK like CloudMade, this makes it very easy to implement custom maps and route's, you'll be able to draw a route between two locations within about 10 minutes of installing the SDK. Here is a quick example to get you started if you go down this route, excuse the pun.

CLLocationCoordinate2D initLocation;

initLocation.longitude = -0.127523;
initLocation.latitude  = 51.51383;

CLLocationCoordinate2D destination;
destination.longitude = -0.125;
destination.latitude = 51;

TokenManager* tokenManager = [[TokenManager alloc] initWithApikey:@"YOUR API KEY"];

CMRoutingManager *routeManager = [[CMRoutingManager alloc] initWithMapView:mapView tokenManager:tokenManager];
[routeManager findRouteFrom:initLocation to:destination onVehicle:CMVehicleWalking];

You can find more information here in the documentation. Another alternative would be to use route-me which would allow you to choose from the following map sources:

OpenStreetMap, Microsoft VirtualEarth, CloudMade, OpenAerialMap, OpenCycleMap, SpatialCloud, and two offline, database-backed formats (DBMap and MBTiles)

Although personally i do not have any experience with route-me, so can't point you in the right direction to get started.

If you are adement on sticking with MKMapView, this blog post will get your started in the right direction.