Displaying google direction api response on Map

Question

I am using google api V3 in my iOS App, I requested to google api direction service, by http GET method, I got a very large json response, I got many alternate routes from origin to destination, now I want to show the route of each alternative on map, how should I done this ? is there any need to integrate google sdk in iOS, or can i use webView only, please help me, and suggest the simplest way. Thanks in advance

Answer 1

you do not need to include any google SDK to draw the route over map. Look at the following classes.

MKPolyline

MKPolyLineview

The google map api Direction service will give you the legs(coordinates) to draw the route between two specific points.

As you already have the json response from the Direction api now you have to parse the json and get all the legs point from the json to create Coordinate array.

Jsonkit for parsing

These points may be or mostly encripted. How to decode the Google Directions API polylines field into lat long points in objective-C for iPhone?

If you have the coordinates array then first you have to create a CLLocationCoordinate2D array like following:

CLLocationCoordinate2D *pointArr        =       malloc(sizeof(CLLocationCoordinate2D) * [your_CoordinateArray count]);

for(int i = 0; i < [your_CoordinateArray count]; i++){
  pointArr[i]       =      [your_CoordinateArray objectAtIndex:i];
}

Then you have to add the polyline to your map

 MKPolyline *line                        = [MKPolyline polylineWithCoordinates:pointArr count:[your_CoordinateArray count]];

    if (nil != line)
    {
        [your_Map addOverlay:line];

    }

Then you have to implement the following map delegate:

- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay
{       

MKOverlayView* overlayView = nil;

lineView                    =       [[MKPolylineView alloc] initWithPolyline:overlay];// lineView is an ivar, object of MKPolylineView
lineView.fillColor          =       [UIColor greenColor];
lineView.strokeColor        =       [UIColor greenColor];

lineView.lineWidth          =       10.0;
lineView.alpha              =       0.9;
overlayView                 =       lineView;

return overlayView;
}    

Now, if you want to show two different routes between two points then you have to create two different array of coordinates and apply the above method for both Arrays

Hope this will help you.

Answer 2

There is no need per say to integrate google sdk and you can simply use webView since I believe the webView gives you alternative views, but the user interface is much cleaner in the SDK than online. But at this moment, I don't believe the SDK allows other apps to show the alternative routes from what I've used of the new SDK. The code in maps.google.com is now considerably different from that in the API and has access to different services. In particular, it has a large external module, mod_suggest.js, that doesn't exist in the API. But you may be able to implement it by

1) Throw the request at maps.google.com, and let it do the suggestions, i.e. open a new browser window and pass it something like http://www.google.com/maps?f=d&source=s_d&saddr=Jurong+West,+Singapore&da ddr=Ang+Mo+Kio,+Singapore&hl=en

2) Just display the normal route and the avoid highways route.

3) Try to guess sensible waypoints to add in the middle of he route that might lead to reasonable alternatives. That's not easy unless you have a database of highways or highway intersections, and can look for such an intersection that's somewhere between your start and end points (for some approximate value of "between").

There may be problems using lat/lng coordinates for the waypoints, particularly if there's a dual carriageway involved. If the coordinates are for a point on the wrong carriageway, GDirections will drive a considerable distance out of your way so that you visit the wrong side of the road. But even using street names you may well get strange kinks near the waypoints, like this:

from: Jurong West, Singapore to: Ayer Rajah Expy singapore to: Ang Mo Kio, Singapore

Perhaps the only way to really deal with that is to include points on both sides of a dual carriageway, and well clear of roads that cross underneath or overhead, and then try to filter out the ones that are silly.

Consider these examples

from: Jurong West, Singapore to: 1.32558,103.740764 to: Ang Mo Kio, Singapore

from: Jurong West, Singapore to: 1.32582,103.740764 to: Ang Mo Kio, Singapore

One of those adds 7 minutes to the trip by a complicated excursion to visit the wrong side of the road.

Writing code to filter out silly routes isn't easy. As a first approximation, you could discard routes that have estimated times that are more than, say, 10% longer than the initial route. And you can also compare the durations for pairs of points on opposite sides of a dual carriageway and always discard the slower one.

Writing code to discard duplicate routes isn't easy either. For example, a point on Bukit Timah Expy or Kranji Expy might create a route that's a duplicate of Google's Seletar Expy suggestion.

You might want to look at: http://www.geocodezip.com/example_geo2.asp?waypts=yes&addr1=Jurong+West,+Singapore&addr2=Ang+Mo+Kio,+Singapore&waypt=Ayer+Rajah+Expy+singapore&geocode=1&geocode=2

But that may not be a legal implementation since the API does not allow it. Hope this helps.