Send Data from JavaScript to Delphi (firemonkey) - delphi

Question

In Delphi , With below code I can send data to Javascript and it work well , but how can send data from Javascript to Delphi ?
first , I Use below code in Javascript but did not work :
JS_DELPHI._geta() ;
even below code did not work :
TMyExtension._geta() ;
I think my code in Delphi have not some essential code.
unit Unit1;
interface
uses
System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Dialogs,
FMX.Controls.Presentation, FMX.StdCtrls, ceffmx, FMX.Edit , ceflib ,
uCEFBaseRefCounted, uCEFInterfaces, uCEFTypes, uCEFListValue, uCEFBrowser, uCEFFrame, uCEFRequest,
uCEFv8Context, uCEFv8Exception, uCEFv8StackTrace, uCEFDomNode, uCEFProcessMessage, uCEFApplicationCore;
type
TForm1 = class(TForm)
ChromiumFMX1: TChromiumFMX;
Button1: TButton;
Edit1: TEdit;
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
type
//这里建议用class 不建议用class(TThread) 不然有些地方要报错
TMyExtension = class(TThread) // or just class, (extension code execute in thread)
public
class function _geta:string;
end;
TCustomRenderProcessHandler = class(TCefRenderProcessHandlerOwn)
protected
procedure OnWebKitInitialized; override;
end;
var
Form1: TForm1;
d : Integer ;
m : TMyExtension ;
CefRenderProcessHandler : TCustomRenderProcessHandler ;
implementation
{$R *.fmx}
{$R *.LgXhdpiPh.fmx ANDROID}
{$R *.XLgXhdpiTb.fmx ANDROID}
{$R *.SSW3.fmx ANDROID}
procedure TForm1.Button1Click(Sender: TObject);
begin
ChromiumFMX1.Load('http://localhost/index.html');
Edit1.Text := '555 ';
ShowMessage('hiiiiiiiiiiiiiiiii');
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
ChromiumFMX1.Browser.MainFrame.ExecuteJavaScript(' d1();',ChromiumFMX1.browser.MainFrame.GetURL, 0);
end;
class function TMyExtension._geta: string;
begin
ShowMessage('dddddddddddddddddddddddd');
Result:='salam';
end;
procedure TCustomRenderProcessHandler.OnWebKitInitialized;
begin
{$IFDEF DELPHI14_UP}
TCefRTTIExtension.Register('JS_DELPHI', TMyExtension);
{$ENDIF}
end;
initialization
CefRemoteDebuggingPort := 9000;
CefRenderProcessHandler := TCustomRenderProcessHandler.Create;
CefBrowserProcessHandler := TCefBrowserProcessHandlerOwn.Create;
end.
end.