How to show Google Maps Alternative Routes on FNC Map

[RANDLE_MR (Ian Randle)]

Hi, I am currently moving a project from WebGMaps to FNCMaps. I am able to show the map and a calculated route (A to B), but I am not able to establish how to show alternative routes. - do you have an example at all please..?

Reviewing FAQs I have established that you have to link a RouteCalculator to the FNCMap and set the option to retrieve alternativeroutes. I also noted that the routes then have to be inspected via the "ARequest.Items" object returned with "RouteCalcGetRouteDirections".

In my example, I have done this, and I can see this object (items) contains 3 routes, but the map displays the first route by default. I want to offer a list of the alternative route options (items array) and when clicked, show this route on the FNCMap. Is there a way to tell the map which route to display (1, 2 or 3), or alternatively replace the route when selected etc...?

If I need to ignore default drawing (by FNC Map) and draw routes manually (from items array), do you have any examples of how I could do this please from the alternatives routes collection..?

Many thanks in advance.
Ian.

[Pieter_Scheldeman (Pieter)]

The option to include alternative routes is only to include them in the calculations, not to display them. You need to manually display them. Below is a piece of code to use:

    for I := 0 to ARequest.Items.Count - 1 do
    begin
      it := ARequest.Items[I];
      arr := it.Coordinates.ToArray;
      with m.AddPolyline(arr) do
      begin
        StrokeColor := gcDarkgoldenrod;
        StrokeWidth := 4;
      end;
    end;

[RANDLE_MR (Ian Randle)]

Thanks Pieter,
The code snip has really helped. I have managed to use this to plot the alternatives to the map.
In follow up, could you confirm the 2 queries below if possible please; thanks.

1. My testing shows that (if enough exist), I seem to get 3 alternative routes. Route 1 of the alternatives also seems to be the main route (default route) that would be plotted without alternatives. - is my assumption correct that you get max of 3, and route 1 is the default..?

2. In the context of the above; is it possible to stop the "default" plot (blue line), so that I can plot all three routes myself using your code snip...? (My rationale is that I will then highlight the route or "alternative" route that the user has selected from a drop-down list). Currently, the default map route is being drawn in blue.

Many thanks in advance.

[Pieter_Scheldeman (Pieter)]

1. Please take a look at the Directions demo, which has a shared UBL.pas layer that contains the code to handle multiple directions. In this sample, the last item is marked in blue, the others are marked in gold/yellow. The amount of alternatives depends on the start & destination & the service. It could be that there are no alternative routes, or there are more than three.

2. When connected & active the route calculator plots the route & adds start & end markers automatically. You could clear them, but then you need to make sure you manually add the necessary information such as start & end markers. You can take a look at the code inside the method RouteCalculatorPlotRoute in FMX.TMSFNCMaps.pas