Geocoding with GMLib on non visual component

Question

I'm using Delphi 10.1 Berlin with GMLib 1.5.5 I can successfully display a map and populate Markers based on data from SQL dataset. But it can be rather slow to drop markers when the result sets of my queries become large. I think a lot of this is due to the overhead of GeoCoding addresses into LatLng.
I would like to GeoCode those address at the time of entry and store the Coordinates making it easier/quicker to display the markers. I wrote a function in my DataModule to GeoCode the address any time it changes (Before Post). But the routine 'hangs' as I don't believe the Map ever gets fully initialized (TGMMap.DoMap)

Here is my function:

procedure GeoCodeAddress(var coords: TLatLng; Address: String);
Var  mMap : TGMMap;
     mBrowser : TWebBrowser;
     mGeoCoder : TGMGeoCode;
begin
     mBrowser := TWebBrowser.Create(Nil);
     mBrowser.Silent := True;
     mMap := TGMMap.Create(Nil);
     mMap.APIKey := GMapsAPIKey;
     mMap.AfterPageLoaded := AfterPageLoaded;
     mMap.WebBrowser := mBrowser;
     mMap.Active := True;
     //mMap.DoMap;
     mGeoCoder := TGMGeoCode.Create(Nil);
     mGeoCoder.Map := mMap;
     mGeoCoder.Geocode(Address);
     if mGeoCoder.GeoStatus = gsOK Then
       Begin
        Coords.Lat := mGeoCoder.GeoResult[0].Geometry.Location.Lat;
        Coords.Lng := mGeoCoder.GeoResult[0].Geometry.Location.Lng;
       End;
     mGeoCoder.Free;
     mMap.Free;
     mBrowser.Free;
end;

procedure AfterPageLoaded(Sender: TObject; First: Boolean);
begin
  if First then
      TGMMap(Sender).DoMap;
end;

Thanks in advance for any suggestions.

score 0 · Answer 1 · answered May 18 '17 at 22:12

0

The problem is that when you call mGeoCoder.Geocode method its possible that the HTML file is not yet loaded.

Try to use mGeoCoder component in AfterPageLoaded event

procedure AfterPageLoaded(Sender: TObject; First: Boolean);
begin
  if First then
  begin
    TGMMap(Sender).DoMap;

    // use here
  end;
end;

answered May 18 '17 at 22:12

cadetill

1,552
16
24

Thanks for the suggestion, but I'm not entirely clear what fires the AfterPageLoaded event. This is on a non-visual data module, so TWebBrowser is never 'shown'. I also have a GMMap and Webbrowser on a form where the user can specify queries, but even though I set the Map.active property in Form Create, the AfterPageLoad doesn't fire until the form is actually shown. – Mike Wilson May 19 '17 at 11:34
Just to follow up, I have not found a way to use GeoCoding without having the browser visible. I know doing this probably violates Google Maps API. I ended up using a 'mini map' display on my main form that turned out to be useful anyway, so I could then use that main form as a vector to do geocoding and cache the result for later display. It definitely speeds up map rendering with many markers. – Mike Wilson May 25 '17 at 13:52

Geocoding with GMLib on non visual component

1 Answers1