How to read the map extents

FNC TMS FNC Maps
1

I haven't found a way of reading the lat/lon extents of the currently displayed TTMSFNCGoogleMap. Is there a way of reading the max and min lat/lon's for the currently displayed map?
Thanks.

2

We are implementing a GetBounds, which will be available in the next release. The code to accomplish this in the current version is:

unit Unit43;

interface

uses
  System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
  FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Dialogs, FMX.TMSFNCGoogleMaps,
  FMX.Controls.Presentation, FMX.StdCtrls;

type
  TForm43 = class(TForm)
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
    m: TTMSFNCGoogleMaps;
  public
    { Public declarations }
  end;

var
  Form43: TForm43;

implementation

{$R *.fmx}

uses
  FMX.TMSFNCMaps, FMX.TMSFNCUtils,
  FMX.TMSFNCTypes, FMX.TMSFNCMapsCommonTypes;

procedure TForm43.Button1Click(Sender: TObject);
var
  s: string;
begin
  s :=
   'function getBounds(){' + LB +
    '  var jsonObj = getDefaultBoundsObject();' + LB +
    '  var loc = ' + MAPVAR + '.getBounds();' + LB +
    '  jsonObj["NorthEast"]["Latitude"] = loc.getNorthEast().lat();' + LB +
    '  jsonObj["NorthEast"]["Longitude"] = loc.getNorthEast().lng();' + LB +
    '  jsonObj["SouthWest"]["Latitude"] = loc.getSouthWest().lat();' + LB +
    '  jsonObj["SouthWest"]["Longitude"] = loc.getSouthWest().lng();' + LB +
    '  return jsonObj;' + LB +
    '}' + LB +
    'getBounds();';

  m.ExecuteJavascript(s,
  procedure(const AValue: string)
  var
    b: TTMSFNCMapsBounds;
    v: string;
  begin
    if AValue = 'null' then
      Exit;

    v := TTMSFNCUtils.URLDecode(AValue);
    b := TTMSFNCMapsBounds.Create;
    try
      b.JSON := v;
      //b.NorthEast;
      //b.SouthWest;
    finally
      b.Free;
    end;
  end
  );
end;

procedure TForm43.FormCreate(Sender: TObject);
begin
  ReportMemoryLeaksOnShutdown := True;
  m := TTMSFNCGoogleMaps.Create(Self);
  m.Parent := Self;
  m.APIKey := 'ENTER API-KEY';
  m.Left := 40;
  m.Top := 40;
end;

end.
3

Thanks Pieter.
I have measured the time taken for the bounds to become available after executing the Javascript to be around 563mSec on my 32 bit tablet. That's too long for what I require so I will wait for the next release to become available.

4

Hi,

The code that is executing JavaScript is the same as we have implemented in GetBounds, so you won't see a difference in timing. Did you test this in debug mode or release mode?

5

I've investigated this further and it appears that at the exact time I was measuring the bounds function duration happened to correspond with the map repositioning. I've moved the timing code such that the map is in a idle state before testing the time taken for the bounds to become available.
On my tablet:
In debug mode it takes 18 - 23mSec
In release mode it takes 15 - 31mSec
So it looks like it is working well and it was my test method that was causing the issue.
Thanks again for supplying the bounds code.

6

Great! Thanks for confirming the implementation is working.